<PAGE>

                                                                   EXHIBIT 10.44

--------------------------------------------------------------------------------


                        THIRD MASTER AMENDMENT AGREEMENT



                           dated as of April 11, 2003

                                      among

                      APEX TRAILER LEASING & RENTALS, L.P.,
                                    as Lessee

                          WABASH NATIONAL CORPORATION,
                                  as Guarantor

                         WABASH STATUTORY TRUST -- 2000,
                                    as Lessor



                         U.S. BANK NATIONAL ASSOCIATION



             (as successor to the corporate trust business of State
                   Street Bank and Trust Company), not in its
               individual capacity except as provided herein, but
                                solely as Trustee



                    THE INSTITUTIONS INDICATED IN SCHEDULE I,
                              as Tranche A Lenders

                           FLEET CAPITAL CORPORATION,
                               as Tranche B Lender

                           FLEET CAPITAL CORPORATION,
                              as Owner Participant

                           FLEET CAPITAL CORPORATION,
                               as Collateral Agent

                                       and

                           FLEET CAPITAL CORPORATION,
                             as Administrative Agent


--------------------------------------------------------------------------------


<PAGE>


                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                                               PAGE
<S>                                                                                                            <C>
ARTICLE I             DEFINITIONS; CONSENT.......................................................................2

         SECTION 1.1           Use of Defined Terms..............................................................2

         SECTION 1.2           Consent...........................................................................2

ARTICLE II            AMENDMENTS.................................................................................2

         SECTION 2.1           Amendments to the Participation Agreement.........................................2

                  (a)      Amendment to Section 6.1(e)(vii)......................................................2

                  (b)      Amendment to Section 6.1(e)(viii).....................................................2

                  (c)      Amendment to Section 6.1..............................................................3

                  (d)      Amendment to Section 10.1.............................................................3

                  (e)      Amendment to Financial Covenants......................................................3

                  (f)      Amendment to Exhibit A................................................................3

         SECTION 2.2           Amendments to Appendix A to the Participation Agreement...........................4

         SECTION 2.3           Amendments to the Lease...........................................................4

                  (a)      Amendment to Section 17.1.............................................................4

ARTICLE III           CONDITIONS TO EFFECTIVENESS................................................................4

         SECTION 3.1           Conditions Precedent..............................................................4

                  (a)      Closing Proceedings...................................................................4

                  (b)      Amendments to Credit Agreement and Note Purchase Agreements...........................4

                  (c)      Fees, Costs and Expenses..............................................................4

                  (d)      Representations and Warranties........................................................5

                  (e)      Fees and Expenses.....................................................................5

ARTICLE IV            MISCELLANEOUS PROVISIONS...................................................................5

         SECTION 4.1           Waiver............................................................................5

         SECTION 4.2           Ratification of and References to the Operative Documents.........................5

         SECTION 4.3           Headings, Etc.....................................................................5

         SECTION 4.4           Counterparts......................................................................5

         SECTION 4.5           Governing Law; Entire Agreement...................................................5

         SECTION 4.6           Instructions to the Trustee.......................................................6
</TABLE>



                                      -i-

<PAGE>



                                TABLE OF CONTENTS
                                   (continued)

<TABLE>
<S>                                 <C>
SCHEDULE I                          Institutions Participating as Tranche A Lenders
SCHEDULE II                         Financial Covenants
SCHEDULE III                        Definitions
SCHEDULE IV                         Fee Schedule

EXHIBIT A                           Compliance Certificate
</TABLE>


                                      -ii-

<PAGE>


                        THIRD MASTER AMENDMENT AGREEMENT

         THIS THIRD MASTER AMENDMENT AGREEMENT (this "Amendment"), dated as of
April 11, 2003, to the Amended and Restated Participation Agreement (the
"Participation Agreement"), dated as of March 30, 2001, and the Amended and
Restated Equipment Lease (the "Lease"), dated as of March 30, 2001, is entered
into by and among APEX TRAILER LEASING & RENTALS, L.P., a Delaware limited
partnership, as the Lessee (in such capacity, together with its permitted
successors, the "Lessee"); WABASH NATIONAL CORPORATION, a Delaware corporation,
as guarantor (the "Guarantor"); WABASH STATUTORY TRUST - 2000, a Connecticut
statutory trust, as Lessor (together with its permitted successors and assigns,
the "Lessor"); U.S. BANK NATIONAL ASSOCIATION (as successor to the corporate
trust business of State Street Bank and Trust Company), not in its individual
capacity, except as set forth herein, but solely as Trustee (the "Trustee" and
in its individual capacity, the "Trust Company"); the Institutions indicated in
Schedule I as "Tranche A Lenders" (each, together with its permitted successors
and assigns, a "Tranche A Lender," and together with the other Tranche A
Lenders, the "Tranche A Lenders"), FLEET CAPITAL CORPORATION, a Rhode Island
corporation ("Fleet Capital"), as the Tranche B Lender (in such capacity,
together with its permitted successors and assigns, the "Tranche B Lender", and
together with the Tranche A Lenders, the "Lenders"); FLEET CAPITAL, as the Owner
Participant (in such capacity, together with its permitted successors and
permitted assigns, the "Owner Participant", and together with the Lenders, the
"Participants"); FLEET CAPITAL, as administrative agent for the Lenders (in such
capacity, together with its permitted successors and assigns, the
"Administrative Agent"); and FLEET CAPITAL, as collateral agent for the Lenders
(in such capacity, together with its permitted successors and assigns, the
"Collateral Agent").

                              W I T N E S S E T H:

         WHEREAS, the Lessee, the Lessor, the Guarantor, the Trustee, the
Lenders, the Owner Participant, the Administrative Agent, and the Collateral
Agent have heretofore entered into a certain Participation Agreement dated March
30, 2001;

         WHEREAS, the Lessee, the Lessor, the Guarantor, the Trustee, the
Lenders, the Owner Participant, the Administrative Agent, and the Collateral
Agent have heretofore entered into a Master Amendment Agreement, dated as of
April 11, 2002, to the Participation Agreement;

         WHEREAS, the Lessee, the Lessor, the Guarantor, the Trustee, the
Lenders, the Owner Participant, the Administrative Agent, and the Collateral
Agent have heretofore entered into a Second Master Amendment Agreement, dated as
of December 13, 2002, to the Participation Agreement;

         WHEREAS, the Lessee and the Lessor have heretofore entered into a
certain Lease dated as of March 30, 2001;

         WHEREAS, the Lessee, the Lessor, the Guarantor, the Trustee, the
Lenders, the Owner Participant, the Administrative Agent, and the Collateral
Agent now desire to amend the Participation Agreement;

         WHEREAS, the Lessee and the Lessor now desire to amend the Lease;



<PAGE>




         NOW, THEREFORE, the parties hereto agree as follows:


                                    ARTICLE I
                              DEFINITIONS; CONSENT


         SECTION 1.1 Use of Defined Terms. Capitalized terms used but not
otherwise defined in this Amendment have the respective meanings specified in
Appendix A to the Participation Agreement; and the rules of interpretation set
forth in Appendix A to the Participation Agreement shall apply to this
Amendment.


         SECTION 1.2 Consent. Subject to the conditions precedent set forth in
Article III below, the Participants, the Collateral Agent and the Administrative
Agent grant their consent to certain transactions as follows:

         (a) In connection with the amendments specified in Article II below,
the Guarantor has informed the Participants, the Collateral Agent and the
Administrative Agent of its intention to amend the Note Purchase Agreements and
the Credit Agreement, in each case in a manner similar to the amendments
hereunder. At the Guarantor's request, the Participants, the Collateral Agent
and the Administrative Agent consent to such amendments.


                                   ARTICLE II
                                   AMENDMENTS


         SECTION 2.1 Amendments to the Participation Agreement.

         (a) Amendment to Section 6.1(e)(vii). Section 6.1(e)(vii) of the
Participation Agreement is hereby amended and restated to read as follows:

                  (vii) as soon as available, and in any event within (30) days
after the last day of each calendar month, (x) a copy of all information
relating to the Equipment subject to the Lease; (y) a copy of one or more
spreadsheets of the Lessee, including the Lessee's master equipment spreadsheet
(the "Equipment Spreadsheets") indicating, among other things, net book value,
appraisal value (where available), rental status, location and the status, sale
or other disposition relating to all trailers owned, leased or otherwise
controlled by the Lessee for such month and (z) a statement setting forth the
account receivables aging for the previous month of the Lessee.

         (b) Amendment to 6.1(e)(viii). Section 6.1(e)(viii) is hereby amended
and restated to read as follows:

                  (viii) in the course of each calendar month, all information
concerning the business or financial condition of the Guarantor as is provided
to (and at the same time as is provided) to the Bank Group, the Receivables
Group, and the Master Equipment Lease parties or any of the Noteholders,
including without limitation, and by no later than fifteen (15) days after the
end of each monthly accounting period of the Guarantor, the following (prepared
in such format and detail as is required by the Administrative Agent): (1) a
statement of projected cash sources and uses of the Guarantor and its
Subsidiaries for the 13 calendar weeks following such end and a report (to the
extent requested by the Administrative Agent from time to time)


                                       2
<PAGE>



containing management's discussion and analysis of such projections and (2) a
statement of cash sources and uses for the immediately preceding monthly
accounting period of the Guarantor and for such historical period as is
reasonably required by the Administrative Agent, in comparative form against the
figures and for the corresponding date and period in the projected cash flow
statements required under the foregoing subsection (1); the foregoing statements
required under subsections (1) and (2) being duly certified by the chief
financial officer or treasurer of the Guarantor.

         (c) Amendment to Section 6.1. Section 6.1 is amended to add new
subsections (n) and (o) which shall read as follows:

                  (n) Deliver Refinancing Commitment Letter. The Lessee and the
Guarantor shall deliver, by no later than January 31, 2004, a commitment letter
or letters (in form and substance satisfactory to the Participants) to refinance
the Obligations.

                  (o) Deliver Business Plan. The Guarantor shall deliver, by no
later than June 30, 2003, a business plan with respect to the Lessee detailing
the Guarantor's operational plans and financial projections for the Lessee for
the immediately following 24 months in a form satisfactory to the Participants.

         (d) Amendment to Section 10.1. Section 10.1 is amended to add a new
subsections (c) and (d) which shall read as follows:

                  (c) The Guarantor acknowledges that it is required to pay
certain closing fees (excluding in any event reimbursement for out of pocket
costs and expenses) to the Participants, the Collateral Agent and the
Administrative Agent in connection with, and as required by, the this Amendment
and comparable amendments to the Note Purchase Agreements and the Credit
Agreement (the "Third Amendment Closing Fees"), including the following: (i)
closing date fees, payable to the Noteholders, the Receivables Group, the
Lenders and the Participants on the date and in the manner set forth below,
calculated based on outstandings as of the Third Amendment Effective Date as set
forth on Schedule IV hereto (the "Closing Date Fees"). The Closing Date Fees are
payable as follows: (a) on the Third Amendment Effective Date, fees not to
exceed $2,000,000 allocated on a pro rata basis among the Noteholders, the
Receivables Group, the Lenders and the Participants and (b) any amount of the
Closing Date Fees which exceed $2,000,000 may at the Guarantor's election be
deferred (the "Deferred Fee Amount") and shall be paid to the Noteholders, the
Receivables Group, the Lenders and the Participants pro rata and on an
equivalent basis as to timing, and shall accrue at a rate per annum equal to the
sum of (A) the rate of interest applicable to Base Rate Loan(s)/Equity
Investments(s) plus (B) (i) 2.00% from the Third Amendment Effective Date until
the date such Deferred Fee Amount has been reduced to $0 plus (ii) 1.00% from
the date such Deferred Fee Amount has been reduced to $0 until January 15, 2004.

                  (d) The Guarantor agrees to pay an additional fee (the
"Additional Fee"), as set forth below, for each and every calendar month in
which the Lessee does not have: (i) a 65% minimum utilization for each of (a)
all the trailers owned, leased or otherwise controlled by the Lessee, including
the Equipment and (b) for all Units of Equipment (as reflected in the Equipment
Spreadsheet for such month, the "Minimum Utilization Requirement") and (ii) a
two hundred dollar ($200.00) minimum average revenue for each of (a) all the
trailers owned, leased or otherwise controlled by the Lessee, including the
Equipment and (b) for all Units of


                                       3
<PAGE>


Equipment (as reflected in the Equipment Spreadsheet for such month, the
"Minimum Average Revenue Requirement"). The Additional Fee is an amount, which
is payable in the aggregate on January 15, 2004, and which shall be calculated
as follows: with respect to each calendar month in which the Minimum Average
Utilization Requirement or the Minimum Average Revenue Requirement are not met
by the Lessee (as reflected in the applicable Equipment Spreadsheet) at a rate
of 0.20% of the Participant Balance outstanding on the last day of such calendar
month. Each calculation of the Additional Fee will be determined without giving
effect to, and shall not be additive of, the Additional Fee in any previous
month.

                  (e) The Guarantor agrees to pay to the Participants on January
15, 2004, a Lease amendment fee (the "Lease Amendment Fee") in an amount equal
to .25% of the Participant Balance outstanding on January 15, 2004.

         (e) Amendment to Financial Covenants. The financial covenants in the
Participation Agreement are amended in their entirety and replaced with the
financial covenants in Schedule II hereto.

         (f) Amendment to Exhibit A. Exhibit A, referred to in Section
6.1(e)(vi), is hereby replaced in its entirety with the Exhibit A (Compliance
Certificate) attached hereto.


         SECTION 2.2 Amendments to Appendix A to the Participation Agreement.

                  Appendix A to the Participation Agreement is amended by adding
or amending the definitions of "Additional Fee", "Applicable Margin", "Closing
Date Fees", "Consolidated EBITDA", "Consolidated Equity", "Deferred Fee Amount",
"Eligible Asset Disposition Charges", "Eligible Asset Impairment Charges",
"Eligible Miscellaneous Non-Cash Charges", "Eligible Restructuring Charges",
"Equipment Spreadsheets", "Lease Amendment Fee", "Minimum Average Revenue
Requirement", "Minimum Utilization Requirement", "Note Purchase Agreement",
"Targeted Consolidated EBITDA Amount", "Third Amendment", "Third Amendment
Closing Fees", "Third Amendment Effective Date" and "Unadjusted Consolidated
EBITDA" as described in Schedule III hereto.


         SECTION 2.3 Amendments to the Lease.

         (a) Amendment to Section 17.1(b). Section 17.1(b) is hereby replaced in
its entirety to read as follows:

                  (b) For purposes of this Section 17.1, "Early Termination
Payment" means an amount equal to (i) for each Unit or Units of Equipment, as
the case may be, computed as of the Early Termination Date, the greater of net
book value of each such Unit or Units and the sale proceeds from the sale of
each such Unit or Units, plus (ii) all Basic Rent then due and owing with
respect to each such Unit or all Units of Equipment, as the case may be, plus
(iii) all other Rent due for each such Unit or all Units of Equipment, as the
case may be, on the Early Termination Date, plus (iv) all accrued and unpaid
Rent owing for periods prior to the Early Termination Date, plus (v) any Break
Costs associated with such early termination.



                                       4
<PAGE>




                                   ARTICLE III
                           CONDITIONS TO EFFECTIVENESS


         SECTION 3.1 Conditions Precedent. The effectiveness of this Amendment
is subject to the following conditions precedent:

         (a) Closing Proceedings. All proceedings taken in connection with this
Amendment and all documents and instruments to be delivered thereon or relating
thereto shall be reasonably satisfactory to each of the Participants and its
counsel, and each of the Participants and its counsel shall have received copies
of such documents as each of the Participants or its counsel may reasonably
request in connection therewith, all in form and substance reasonably
satisfactory to each of the Participants and its counsel.

         (b) Amendments to Credit Agreement and Note Purchase Agreements. The
amendments to the Credit Agreement and Note Purchase Agreements, providing for
covenants of the Guarantor no more restrictive than the covenants set forth
herein and entered into by the Guarantor, the Bank Group and the Noteholders,
shall have been duly executed and delivered by the parties thereto and such
amendments shall be in full force and effect and no default shall exist in the
performance by any party of any of its obligations under such agreements.

         (c) Fees, Costs and Expenses. The Lessee shall have paid to the
Participants all fees, costs and expenses due under the Operative Documents,
including, but not limited to, the Closing Date Fees payable to the Participants
in an aggregate amount equal to 0.375% of aggregate Participant Balance
calculated in accordance with Section 2.1(d) above.

         (d) Representations and Warranties. The Lessee and the Guarantor hereby
represent and warrant that (i) this Amendment and the Participation Agreement as
amended hereby constitute legal, valid and binding obligations of each of the
Lessee and the Guarantor and are enforceable against each of the Lessor and the
Guarantor in accordance with their terms; and (ii) the representations and
warranties of the Lessee and the Guarantor set forth in the Operative Documents
(or in certificates delivered pursuant thereto) executed by any thereof shall be
true and correct in all respects as though made on and as of such date, except
to the extent such representations or warranties relate solely to an earlier
date, in which case such representations and warranties shall have been true and
correct in all respects on and as of such earlier date.

         (e) Fees and Expenses. The Lessee shall have paid all the reasonable
fees, costs and expenses incurred by Mayer, Brown, Rowe & Maw, as counsel to the
Participants, the Collateral Agent and the Administrative Agent hereunder, in
connection with the execution and delivery of this Amendment.


                                   ARTICLE IV
                            MISCELLANEOUS PROVISIONS

         SECTION 4.1 Waiver. The execution, delivery and effectiveness of this
Amendment shall not, except as expressly provided herein, operate as a waiver of
any right, power or remedy of the Participants, the Collateral Agent or the
Administrative Agent, nor constitute a waiver of any provision of the
Participation Agreement or any other documents, instruments and agreements
executed and/or delivered in connection therewith.



                                       5
<PAGE>



         SECTION 4.2 Ratification of and References to the Operative Documents.
This Amendment shall be deemed to be an amendment to the Participation Agreement
and as such agreement is amended hereby, is hereby ratified, approved and
confirmed in each and every respect. All references to any such Operative
Document in any other document, instrument, agreement or writing shall hereafter
be deemed to refer to such Operative Document as amended hereby.


         SECTION 4.3 Headings, Etc. The Table of Contents and headings of the
various Articles, Sections and clauses of this Amendment are for convenience of
reference only and shall not modify, define, expand or limit any of the terms or
provisions hereof.


         SECTION 4.4 Counterparts. This Amendment may be executed by the parties
hereto in separate counterparts, each of which when so executed and delivered
shall be deemed to be an original, but all such counterparts shall together
constitute but one and the same instrument.


         SECTION 4.5 Governing Law; Entire Agreement. THIS AMENDMENT AND EACH
OTHER OPERATIVE DOCUMENT EXECUTED IN CONNECTION HEREWITH SHALL EACH BE DEEMED TO
BE A CONTRACT MADE UNDER AND GOVERNED BY THE LAW OF THE COMMONWEALTH OF
MASSACHUSETTS (EXCLUDING ANY CONFLICT-OF-LAW OR CHOICE-OF-LAW RULES WHICH MIGHT
LEAD TO THE APPLICATION OF THE INTERNAL LAWS OF ANY OTHER JURISDICTION) AS TO
ALL MATTERS OF CONSTRUCTION, VALIDITY AND PERFORMANCE. This Amendment and the
other Operative Documents constitute the entire understanding among the parties
hereto with respect to the subject matter hereof and supersede any prior
agreements, written or oral, with respect thereto.


         SECTION 4.6 Instructions to the Trustee. The undersigned Participants,
Collateral Agent and Administrative Agent hereby authorize and direct the
Trustee to enter into, execute and deliver this Amendment and perform all of the
obligations of the Trustee and Lessor hereunder.



                                       6
<PAGE>





         IN WITNESS WHEREOF, the parties hereto have caused this AMENDMENT to be
executed by their respective officers thereunto duly authorized as of the date
and year first above written.

                             APEX TRAILER LEASING & RENTALS, L.P.,
                                      as Lessee

                             By:      Wabash National Corporation,
                                      General Partner




                                      By:_______________________________________
                                               Name:
                                               Title:

                             WABASH NATIONAL CORPORATION,
                                      as Guarantor




                             By:________________________________________________
                                Name:
                                Title:


                             WABASH STATUTORY TRUST -- 2000

                             By:    U.S. BANK NATIONAL ASSOCIATION (as successor
                                    to the corporate trust business of State
                                    Street Bank and Trust Company), not in its
                                    individual capacity but solely in its
                                    capacity as Trustee



                             By:________________________________________________
                                Name:
                                Title:


<PAGE>



                             U.S. BANK NATIONAL ASSOCIATION (as successor to the
                             corporate trust business of State Street Bank and
                             Trust Company), not in its individual capacity,
                             except as provided herein, but solely as Trustee




                             By:________________________________________________
                                Name:
                                Title:

                             U.S. BANK, NATIONAL ASSOCIATION
                             (formerly known as FIRSTAR BANK, N.A.)
                                        as Tranche A Lender




                             By:________________________________________________
                                Name:
                                Title:

                             GENERAL ELECTRIC CAPITAL
                             CORPORATION,
                                      as Tranche A Lender




                             By:________________________________________________
                                      Name:
                                      Title:


<PAGE>


                             NATIONAL CITY BANK OF INDIANA,
                                  as Tranche A Lender




                             By:________________________________________________
                                  Name:
                                  Title:



                             FLEET CAPITAL CORPORATION,
                                  as Tranche B Lender




                             By:________________________________________________
                                  Name:
                                  Title:

                             FLEET CAPITAL CORPORATION,
                                  as Owner Participant




                             By:________________________________________________
                                  Name:
                                  Title:

                             FLEET CAPITAL CORPORATION,
                                  as Administrative Agent




                             By:________________________________________________
                                  Name:
                                  Title:

                             FLEET CAPITAL CORPORATION,
                                  as Collateral Agent




                             By:________________________________________________
                                  Name:
                                  Title:


<PAGE>

                                                                      SCHEDULE I
                                             TO THIRD MASTER AMENDMENT AGREEMENT


                 INSTITUTIONS PARTICIPATING AS TRANCHE A LENDERS


TRANCHE A LENDERS:

U.S. Bank, National Association
(formerly known as Firstar Bank, N.A.)
7th & Washington, 7th Floor
St. Louis, MO  63101
Attention:        Alan R. Milster
                  Vice President
Phone:            (314) 418-2468
Fax:              (314) 418-2135
Email:            alan.r.milster@usbank.com


National City Bank of Indiana
One National City Center
Suite 200E
Indianapolis, IN  46255
Attention:        Lex Curry
Phone:            (317) 267-3668
Fax:              (317) 267-8899
Email:            lex.curry@national-city.com


General Electrical Capital-Capital Funding Inc.
301 Merritt 7
Suite 23
Norwalk, CT 06851
Attention:        Howard Norowitz
Phone:            (203) 229-1821
Fax:              (203) 229-1922
Email:            howard.norowitz@ge.com

Attention:        Ben Faustini
Phone:            (203) 229-1836
Fax:              (203) 229-1922
Email:            sebastian.faustini@ge.com


                                      I-i

<PAGE>





                                                                     SCHEDULE II
                                             TO THIRD MASTER AMENDMENT AGREEMENT


                               FINANCIAL COVENANTS

For purposes of this Schedule II to the Third Master Amendment Agreement,
capitalized terms used herein and not otherwise defined shall have (a) the
meanings set forth in Schedule III, or (b) to the extent such term is not
defined in such Schedule III, the meanings set forth in Appendix A to the
Participation Agreement.

Financial Covenants. The Lessee or the Guarantor, as the case may be, shall
comply with the following:

         1.       Minimum Consolidated Equity. The Guarantor shall, as of the
                  last day of each of the fiscal quarters specified below,
                  maintain Consolidated Equity at an amount not less than the
                  applicable "Minimum Consolidated Equity" specified below:

<TABLE>
<CAPTION>
Fiscal Quarter Ending                    Minimum Consolidated
---------------------                    --------------------
                                                Equity
                                                ------
<S>                                     <C>
March 31, 2003                               $40,000,000
June 30, 2003                                $35,000,000
September 30, 2003                           $30,000,000
December 31, 2003                            $25,000,000
</TABLE>

         2.       Maximum Leverage Valuation Ratio. The Guarantor shall not
                  permit, as of the last day of each of the fiscal quarters
                  specified below, the Leverage Valuation Ratio to exceed the
                  applicable "Maximum Leverage Valuation Ratio" specified below:

<TABLE>
<CAPTION>
Fiscal Quarter Ending                Maximum Leverage Valuation
---------------------                --------------------------
                                                Ratio
                                                -----
<S>                                  <C>
March 31, 2003                               0.95 to 1
June 30, 2003                                0.95 to 1
September 30, 2003                           0.95 to 1
December 31, 2003                            0.95 to 1
</TABLE>

                                      II-i

<PAGE>




         3.       Minimum Consolidated EBITDA. The Guarantor shall, as of the
                  last day of the calendar months specified below, maintain
                  Consolidated EBITDA at an amount not less than the applicable
                  "Minimum Cumulative Consolidated EBITDA" specified below for
                  the period commencing on January 1, 2003 and ending on such
                  last day:
<TABLE>
<CAPTION>
Month Ending                        Minimum Rolling 12 Month
------------                        ------------------------
                                      Consolidated EBITDA
                                      -------------------
<S>                                 <C>
March 31, 2003                            $0
June 30, 2003                             $5,000,000
September 30, 2003                        $15,000,000
December 31, 2003                         $20,000,000
</TABLE>

         4.       Maximum Capital Expenditures. The Guarantor will not, and will
                  not permit any Subsidiary to, expend for Capital Expenditures
                  during any fiscal year of the Guarantor or its Subsidiaries,
                  in excess of $4,000,000 in the aggregate for the Guarantor and
                  its Subsidiaries.

         5.       Maximum Finance Contracts. The Lessee and the Guarantor will
                  not, and will not permit any of their respective Subsidiaries
                  to, enter into any new Finance Contract if and to the extent
                  that the sum of such Finance Contract (a) when added to the
                  aggregate amount of all Finance Contracts entered into by the
                  Lessee or the Guarantor or such Subsidiaries during the twelve
                  (12) month period that commences on the Amendment Closing Date
                  exceeds $5,000,000 or (b) when added to the aggregate amount
                  of all Finance Contracts entered into by the Lessee or the
                  Guarantor or such Subsidiaries during the twelve (12) month
                  period that commences on the first (1st) anniversary of the
                  Amendment Closing Date exceeds $5,000,000.

                                     II-ii

<PAGE>



                                                                    SCHEDULE III
                                             TO THIRD MASTER AMENDMENT AGREEMENT


                                   DEFINITIONS

         "Additional Fee" is defined in Section 10.1(d).

         "Applicable Margin" shall mean the sum of (x) the per annum rates
constituting the Applicable Margin, as set forth in the chart below plus (y) the
"Additional Fee" described in Section 10.1(d):*

<TABLE>
<CAPTION>
APPLICABLE MARGIN WITH         APPLICABLE MARGIN WITH RESPECT TO      APPLICABLE MARGIN WITH
RESPECT TO TRANCHE A AND       EURODOLLAR EQUITY INVESTMENTS          RESPECT TO BASE RATE
TRANCHE B EURODOLLAR LOANS                                            LOAN(S)/EQUITY INVESTMENT(s)
--------------------------------------------------------------------------------------------------
<S>                            <C>                                    <C>
         4.30%                              5.25%                                 2.00%
--------------------------------------------------------------------------------------------------
</TABLE>

         "Closing Date Fees" are defined in Section 10.1(c).

         "Consolidated EBITDA" means, for any period, on a consolidated basis
for the Guarantor and its consolidated Subsidiaries, the sum of the amounts for
such period, without duplication, of (i) Consolidated Operating Income, plus
(ii) charges against income for foreign taxes and U.S. income taxes to the
extent deducted in computing Consolidated Operating Income, plus (iii) Interest
Expense to the extent deducted in computing Consolidated Operating Income, plus
(iv) depreciation expense to the extent deducted in computing Consolidated
Operating Income, plus (v) amortization expense, including, without limitation,
amortization of goodwill and other intangible assets to the extent deducted in
computing Consolidated Operating income, plus (vi) Eligible Asset Disposition
Charges to the extent deducted in computing Consolidated Operating Income, plus
(vii) Eligible Asset Impairment Charges to the extent deducted in computing
Consolidated Operating Income, plus (viii) Eligible Miscellaneous Non-Cash
Charges to the extent deducted in computing Consolidated Operating Income, plus
(ix) Eligible Restructuring Charges to the extent deducted in computing
Consolidated Operating Income, minus (a) the total interest income of the
Guarantor and its Subsidiaries to the extent included in computing Consolidated
Operating Income minus (b) the total tax benefit reported by the Guarantor and
its Subsidiaries to the extent included in computing Consolidated Operating
Income.

         "Consolidated Equity" means as of the date of any determination thereof
for any relevant period, the total stockholders' equity of the Guarantor and its
Subsidiaries on a consolidated basis, as determined in accordance with Agreement
Accounting Principles, plus the sum of the amounts for such period, without
duplication, of (i) foreign currency translation and transaction gains and
losses, plus (ii) all charges against income for foreign taxes and U.S. income
taxes,

                                     III-i

<PAGE>


plus (iii) Eligible Asset Disposition Charges, plus (iv) Eligible Asset
Impairment Charges, plus (v) Eligible Non-Cash Miscellaneous Charges, plus (vi)
Eligible Restructuring Charges.

         "Deferred Fee Amount" is defined in Section 10.1(c).

         "Eligible Asset Disposition Charges" means charges, calculated in
accordance with Agreement Accounting Principles, incurred by the Guarantor in
its fiscal year ending on December 31, 2003 but only to the extent (i) such
charges relate solely and directly to the sales of assets and properties.

         "Eligible Asset Impairment Charges" means up to $35,000,000
attributable to, without duplication, any charges incurred by the Guarantor in
its fiscal year ending on December 31, 2003 but only to the extent such charges
relate solely and directly to the impairment of long-lived assets, goodwill and
other intangible assets, all in accordance with Agreement Accounting Principles.

         "Eligible Miscellaneous Non-Cash Charges" means non-cash charges
(including but not limited to non-cash losses on finance contracts, severance
and other loss contingencies), calculated in accordance with Agreement
Accounting Principles and, to the extent deducted in computing Consolidated
Operating Income, incurred by the Guarantor in its fiscal year ending on
December 31, 2003 but only to the extent the aggregate amount of Eligible
Miscellaneous Non-Cash Charges do not exceed $10,000,000.

         "Eligible Restructuring Charges" means any charges incurred by the
Guarantor in its fiscal year ending on December 31, 2003 but only to the extent
such charges (i) are incurred in accordance with Agreement Accounting Principles
and (ii) relate solely and directly to the restructuring, waiving or amending of
the instruments and documents evidencing any of the Secured Obligations and
other lines of credit, leases or other extensions of credit, including any
amounts paid to any lenders, advisor fees and other related costs.

         "Equipment Spreadsheets" is defined in Section 6.1(e)(vii).

         "Lease Amendment Fee" is defined in Section 10.1(e).

         "Minimum Average Revenue Requirement" is defined in Section 10.1(d).

         "Minimum Utilization Requirement" is defined in Section 10.1(d).

         "Note Purchase Agreement" or "Note Purchase Agreements" means any of
those certain Note Purchase Agreements dated as of December 1, 1996, January 31,
1996 or September 29, 2000 among the Guarantor and the Noteholders thereunder as
subsequently amended or restated.

         "Targeted Consolidated EBITDA Amount" means, for each relevant month,
the cumulative Consolidated EBITDA amount (measured from and after January 1,
2003) furnished on March 6, 2003 to the Lenders as part of the Guarantor's 2003
budget minus that portion of such cumulative Consolidated EBITDA amount which is
attributable to the sale of any assets or any Subsidiary to the extent permitted
herein or otherwise approved by the Required Lenders.


                                     III-ii

<PAGE>


         "Third Amendment" means that certain Third Amendment dated as of April
11, 2003 among the Lessee, the Guarantor, the Lessor, the Trustee, the Lenders,
the Owner Participant, the Administrative Agent and the Collateral Agent.

         "Third Amendment Closing Fees" are defined in Section 10.1(c).

         "Third Amendment Effective Date" means April 11, 2003.

         "Unadjusted Consolidated EBITDA" means, for any period, on a
consolidated basis for the Guarantor and its consolidated Subsidiaries, the sum
of the amounts for such period, without duplication, of (i) Consolidated
Operating Income, plus (ii) charges against income for foreign taxes and U.S.
income taxes to the extent deducted in computing Consolidated Operating Income,
plus (iii) Interest Expense to the extent deducted in computing Consolidated
Operating Income, plus (iv) depreciation expense to the extent deducted in
computing Consolidated Operating Income, plus (v) amortization expense,
including, without limitation, amortization of goodwill and other intangible
assets to the extent deducted in computing Consolidated Operating Income, plus
(vi) Eligible Asset disposition Charges to the extent deducted in computing
Consolidated Operating Income, minus (a) the total interest income of the
Guarantor and its Subsidiaries to the extent included in computing Consolidated
Operating Income minus (b) the total tax benefit reported by the Guarantor and
its Subsidiaries to the extent included in computing Consolidated Operating
Income.


                                    III-iii

<PAGE>


                                                                     SCHEDULE IV
                                             TO THIRD MASTER AMENDMENT AGREEMENT

         CLOSING DATE FEES*
         -----------------
         (Payable in part on the Third Amendment Effective Date and in part on
         a deferred basis)

<TABLE>
<CAPTION>
PARTY TO RECEIVE FEE         FEE RATE         THIRD AMENDMENT EFFECTIVE DATE
--------------------         --------         ------------------------------
                                              AGGREGATE OUTSTANDINGS
                                              ----------------------
<S>                          <C>              <C>
Lenders                      .625%            $_____________
Noteholders                  .625%            $_____________
Receivables Group            .375%            $_____________
Participants                 .375%            $_____________
</TABLE>


         Fees are calculated for each Person by multiplying the applicable Fee
Rate by the amount of outstandings, as set forth above opposite such Person's
name.


                                     III-i

<PAGE>


                                                                       EXHIBIT A
                                             TO THIRD MASTER AMENDMENT AGREEMENT

                    FORM OF AUTHORIZED OFFICER'S CERTIFICATE
                                  OF COMPLIANCE


To:  The Participants, Lessor, Collateral Agent and Administrative Agent to the
     Third Master Amendment Agreement Described Below

                  This Compliance Certificate is furnished pursuant to that
certain Third Master Amendment Agreement dated as of April 11, 2003 (as amended,
modified, renewed or extended from time to time, the "Agreement") among APEX
TRAILER LEASING & RENTALS, L.P., a Delaware limited partnership, as the Lessee
(in such capacity, together with its permitted successors, the "Lessee"); WABASH
NATIONAL CORPORATION, a Delaware corporation, as guarantor (the "Guarantor");
WABASH STATUTORY TRUST - 2000, a Connecticut statutory trust, as Lessor
(together with its permitted successors and assigns, the "Lessor"); U.S. BANK
NATIONAL ASSOCIATION (as successor to the corporate trust business of State
Street Bank and Trust Company), not in its individual capacity, except as set
forth therein, but solely as Trustee (the "Trustee" and in its individual
capacity, the "Trust Company"); the Institutions indicated in Schedule I thereto
as "Tranche A Lenders" (each, together with its permitted successors and
assigns, a "Tranche A Lender," and together with the other Tranche A Lenders,
the "Tranche A Lenders"), FLEET CAPITAL CORPORATION, a Rhode Island corporation
("Fleet Capital"), as the Tranche B Lender (in such capacity, together with its
permitted successors and assigns, the "Tranche B Lender", and together with the
Tranche A Lenders, the "Lenders"); FLEET CAPITAL, as the Owner Participant (in
such capacity, together with its permitted successors and permitted assigns, the
"Owner Participant", and together with the Lenders, the "Participants"); FLEET
CAPITAL, as administrative agent for the Lenders (in such capacity, together
with its permitted successors and assigns, the "Administrative Agent"); and
FLEET CAPITAL, as collateral agent for the Lenders (in such capacity, together
with its permitted successors and assigns, the "Collateral Agent"). Unless
otherwise defined herein, capitalized terms used in this Compliance Certificate
have the meanings ascribed thereto in the Agreement.

         THE UNDERSIGNED HEREBY CERTIFIES THAT:

                  1. I am the duly elected _________________ of the [Lessee]
[Guarantor] and the [Chief Financial Officer] [Treasurer];

                  2. I have reviewed the terms of the Agreement and I have made,
or have caused to be made under my supervision, a detailed review of the
transactions and conditions of the [Lessee] [Guarantor] and its Subsidiaries
during the accounting period covered by the attached financial statements;

                  3. The examinations described in paragraph 2 did not disclose,
and I have no knowledge of, the existence of any condition or event which
constitutes a Lease Event of Default

                                      -i-

<PAGE>

or Unmatured Lease Default during or at the end of the accounting period covered
by the attached financial statements or as of the date of this Certificate,
except as set forth below; and

                  4. Schedule I and Schedule II attached hereto set forth
financial data and computations evidencing the [Lessee] [Guarantor]'s compliance
with certain covenants of the Agreement during the accounting period covered by
the attached financial statements, all of which data and computations are true,
complete and correct.

                  Described below are the exceptions, if any, to paragraph 3,
listing, in detail, the nature of the condition or event, the period during
which it has existed and the action which the [Lessee] [Guarantor] has taken, is
taking, or proposes to take with respect to each such condition or event:

-----------------------------------------------------------------

-----------------------------------------------------------------


                                      -ii-

<PAGE>



                  The foregoing certifications, together with the computations
set forth in Schedule I and Schedule II hereto and the financial statements
delivered with this Certificate in support hereof, are made and delivered this
_____ day of __________, ____.


                                        --------------------------------
                                            [Insert Name of Officer]


                                     -iii-

<PAGE>



                                            SCHEDULE I TO COMPLIANCE CERTIFICATE

[Wabash National Corporation] [Apex Trailer Leasing & Rentals, L.P.]
Quarterly Compliance Certificate Worksheet

                             COMPLIANCE CERTIFICATE
          QUARTERLY SCHEDULE OF COMPLIANCE AS OF _______________, 2003
                             (DOLLARS IN THOUSANDS)

<TABLE>
<S>                                                                                    <C>
A.       MAXIMUM LEVERAGE VALUATION RATIO

         1.       Actual Amount:
                  a.       Term Debt (Notes & Bank Debt)
                  b.       Revolver (Super Revolver)
                                                                                        -----------
                  c.       Total Debt (a+b)                                             $        -
                  d.       Cash and Cash Equivalents
                  e.       Net Inventory
                  f.       Net Prepaid and Other Expenses
                  g.       Net PP&E
                                                                                        -----------
                  h.       Total Assets (d+e+f+g)                                       $        -
                  i.       Leveraged Ratio (c/h)                                                  x

         2.       Minimum Required Amount                                                         x

B.       MAXIMUM CAPITAL EXPENDITURES

         1.       Actual Amount:
                  a.       Capital Expenditures (Year-to-Date)                          $        -

         2.       Maximum Annual Allowed Amount                                         $     4,000

C.       MAXIMUM FINANCE CONTRACTS

         1.       Actual Amount:
                  a.       Finance Contracts (Year-To-Date)                             $        -

         2.       Maximum Annual Allowed Amount                                         $     5,000

D.       MINIMUM CONSOLIDATED CUMULATIVE (SINCE 1/1/2003) EBITDA

         1.       Actual Amount:

                  a.       Consolidated Operating Income                                           $    -
                  b.       Foreign and Domestic Taxes Deducted in Operating Income                 $    -
                  c.       Interest Expense Deducted in Operating Income                           $    -
                  d.       Eligible Asset Disposition Charges                                      $    -
                  e.       Eligible Asset Impairment Charges                                       $    -
                  f.       Eligible Miscellaneous Non-Cash Charges                                 $    -
                  g.       Eligible Restructuring Charges                                          $    -
</TABLE>


                                      -iv-

<PAGE>


<TABLE>
<S>                                                                                     <C>
                  h.       Depreciation Expense Deducted in Operating Income                       $    -
                  i.       Amortization Expense Deducted in Operating Income                       $    -
                  j.       Interest Income Included in Operating Income                            $    -
                  k.       Total Tax Benefit Included in Operating Income                          $    -
                  l.       Consolidated EBITDA (a+b+c+d+e+f-g-h)                                   $    -

         2.       Minimum Required Amount                                               $     -

E.       MINIMUM CONSOLIDATED EQUITY

         1.       Actual Amount:

                  a.       Consolidated Equity                                          $     -
                  b.       Minimum Required Amount                                      $     -
</TABLE>

                                      -v-

<PAGE>



<TABLE>
<S>                                                                                <C>
A.       MAXIMUM OTHER UNSECURED INDEBTEDNESS

         1.       Actual Amount                                                     $_____________

         2.       Maximum Permitted Amount:                                         $3,000,000

B.       SALES OF ASSETS

         1.       Actual Amount:

                  a.       Total amount of sales of assets in current fiscal
                           year to date (See Schedule II for detail)                $_____________

         2.       Maximum Permitted Amount:                                         $5,000,000

C.       INVESTMENTS

         For each new Investment pursuant to Section 6.3(D)(vii) of the Credit
         Agreement during the most recent fiscal quarter covered by this
         Certificate, complete the following:

         1.       Date and brief description of nature of new Investment:

                  -------------------------------------------------------

                  -------------------------------------------------------

         2.       Actual Amount:

                  a.       Amount of new Investment                                 $_____________

                  b.       Amount of existing Investments                           +_____________

                  c.       Total Investments                                        =$____________

         3.       Maximum Permitted Amount:                                         $5,000,000

D.       LEASES

         1.       Actual Amount of Leases:                                          $__________

         2.       Maximum Permitted Amount:                                         $5,000,000
</TABLE>


                                      -vi-

<PAGE>




                                           SCHEDULE II TO COMPLIANCE CERTIFICATE

                  Schedule of Compliance as of __________, ____

                             (Dollars in Thousands)

A.       Sales of Assets

         [List separate sales and amounts]                        $_____________
                                                                  ______________
                                                                  ______________
                                                                  ______________
                                                                  ______________

                                                     Total        $_____________



                                     -vii-