<PAGE>

                                                                   Exhibit 10.18

                                    AMENDMENT

         THIS AMENDMENT, dated as of December 21, 1999 (the "Amendment") is to
the Consulting Agreement dated as of April 29, 1998 (the "Consulting Agreement")
by and between Grove Worldwide LLC, a Delaware limited liability company (the
"Company") and George Group, Inc., a Texas corporation (the "Consultant").

                                   WITNESSETH

         WHEREAS, the Company and the Consultant are parties to the Consulting
Agreement; and

         WHEREAS, the Company and the Consultant desire to amend the Consulting
Agreement, subject to the conditions set forth herein.

         NOW, THEREFORE, in consideration of the premises and mutual agreements
contained herein, and for other good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the Company and the Consultant
hereby agree as follows:

         1.       DEFINED TERMS. Unless otherwise defined herein, terms defined
                  in the Consulting Agreement shall have such meanings when used
                  herein.

         2.       TERM. The term of the Consulting Agreement is the period
                  commencing on the Effective Date and ending on December 31,
                  1999. The "Term" and the "Performance Term" as previously
                  defined are amended to reflect this new ending date.

         3.       ADVISORY SERVICES. The remaining Services to be provided by
                  the Consultant are set forth in Exhibit B, attached hereto and
                  incorporated by reference herein. The Plan as set forth in
                  Exhibit A is hereby superseded and replaced in its entirety by
                  Exhibit B.

         4.       COMPENSATION. The Monthly Fees and Expenses specified in the
                  Plan are modified in accordance with the revised staffing and
                  project focus in Exhibit B. The Company agrees to pay the
                  Consultant's actual expenses from the date of the Amendment
                  through the remainder of the Term. All other payment terms
                  (E.G., Adjustment, Consultant Bill) remain in effect and
                  unchanged.

                  The last sentence of the first paragraph of Section 4.1 is
                  deleted and replaced in its entirety with the following:

                           The actual out-of-pocket expenses of the Consultant
                           ("Actual Expenses" as reported in the Monthly Expense
                           Reconciliation Report ("Monthly

<PAGE>

                           Report") submitted to the Company) will be calculated
                           at the end of the Term of this Agreement and fifty
                           percent (50%) of the excess, if any, of (a) the total
                           "Invoiced Expenses" (as reported in the Monthly
                           Report) over (b) such Actual Expenses of the
                           Consultant to such date shall be reimbursed by
                           Consultant to the Company promptly following the
                           determination thereof.

         5.       PUBLICITY. In addition to the provisions of Section 6.3 of the
                  Consulting Agreement, neither the Consultant nor the Company
                  shall make any public statement concerning this Amendment
                  without the prior express written consent of the other party.
                  The Company and the Consultant shall agree upon the text of a
                  joint statement announcing the changed business relationship
                  under this Amendment.

         6.       SOLICITATION. Notwithstanding the provisions of Section 7.2 of
                  the Consulting Agreement, the Consultant grants permission to
                  the Company to speak to and negotiate with the employees of
                  the Consultant listed in Exhibit B for potential employment
                  with the Company.

         7.       TERMINATION. For purposes of adjustments to Class B Percentage
                  Interests of the Consultant under Section 4.5 of the LLC
                  Agreement, this Amendment shall constitute termination of the
                  Consulting Agreement.

         8.       POST-TERMINATION OBLIGATIONS. The second sentence of Section
                  8.3 (a) is deleted in its entirely and replaced by the
                  following:

                           The Actual Expenses of Consultant will be calculated
                           at the effective date of the termination of this
                           Agreement and fifty percent (50%) of the excess of
                           (a) the Invoiced Expenses funded through such date
                           (as set forth in the Plan and the Monthly Report)
                           over (b) such Actual Expenses of Consultant to such
                           date shall be reimbursed by Consultant to the Company
                           promptly following the determination thereof.

         9.       AMENDMENTS. As a written instrument duly executed by both
                  parties, this Amendment satisfies the requirements of Section
                  11 of the Consulting Agreement to effectuate the amended
                  provisions contained herein.

         10.      CONTINUING EFFECT OF CONSULTING AGREEMENT. This Amendment
                  shall not constitute a waiver, amendment, or modification of
                  any other provision of the Consulting Agreement not expressly
                  referred to herein. Except as expressly amended or modified
                  herein, the provisions of the Consulting Agreement are and
                  shall remain in full force and effect.

<PAGE>

         11.      COUNTERPARTS. This Amendment may be executed in two or more
                  counterparts, each of which shall be an original and all of
                  which together constitute one and the same instrument.

         12.      EFFECTIVENESS. This Amendment shall be effective upon receipt
                  by the Company and the Consultant of counterparts hereof, duly
                  executed and delivered by the parties.

         IN WITNESS WHEREOF, each party hereto has caused this Amendment to be
duly executed by its duly authorized representative as of the day and year first
above written.

ADDRESS:                                             GROVE WORLDWIDE LLC
1565 Buchanan Trail East
P. O. Box 21
Shady Grove, PA 17256                                By:
                                                         ----------------------
Attention:     Jeffry D. Bust                               Jeffry D. Bust

                                                     Title:   Chairman & CEO

ADDRESS:                                             GEORGE GROUP, INC.
One Galleria Tower
13355 Noel Road, Suite 1100
Dallas, Texas  75240                                          By:
                                                         ----------------------
Attention:     James Storie                          Michael George
               Les Park                              Title:  CEO

<PAGE>

                                    EXHIBIT B

                       Revised Staffing and Project Focus
<TABLE>
<CAPTION>

                    Original                      New                    Original                 New Cost
Date              Staffing Plan             Staffing Plan              Cost to Grove              to Grove
----              -------------             -------------              -------------              --------

<S>                        <C>                       <C>               <C>                      <C>
Oct. 99                    19                        19                $   297,000              $  297,000

Nov. 99                    19                        16                $   297,000              $  247,000

Dec. 99                    16                        13                $   297,000              $  217,000



                                                                                *
                                                                                *

                                                                       ----------                ---------
                                               TOTAL                   $ 3,751,000              $  761,000
                                            TOTAL GROVE SAVINGS                                 $2,990,000
</TABLE>

Note: Grove would like to speak to the following individuals about potential
employment with Grove:

<TABLE>
<CAPTION>
                -------------------------------- -----------------------------------------------
                         GGI Personnel                              Project

                -------------------------------- -----------------------------------------------
                <S>      <C>                     <C>
                1.       Pleiman, David          Manlift Product Development Team

                -------------------------------- -----------------------------------------------
                2.       Nissen, Christine       Manlift Product Development Team

                -------------------------------- -----------------------------------------------
                3.       Gordon, John            Manlift Product Program Leader

                -------------------------------- -----------------------------------------------
                4.       Sendell, Scott          Strategic Procurement Outsourcing

                -------------------------------- -----------------------------------------------
                5.       McGovern, Mark          Crane Operations

                -------------------------------- -----------------------------------------------
                6.       Blackwell, Dan          Crane Operations

                -------------------------------- -----------------------------------------------
</TABLE>