<PAGE>

EXHIBIT 4.4


     FINANCIAL                          FINANCIAL GUARANTY
     SECURITY                           INSURANCE POLICY
     ASSURANCE

<TABLE>
     <S>                                                              <C>
     OBLIGOR: AmeriCredit Automobile Receivables Trust 2000-A         Policy No.:  50902-N
     OBLIGATIONS: $1,300,000,000 Asset Backed Notes, in the Classes   Date of Issuance:
               described in Endorsement No. 1 hereto                  February 11, 2000
</TABLE>

     FINANCIAL SECURITY ASSURANCE INC. ("Financial Security"), for consideration
received, hereby UNCONDITIONALLY AND IRREVOCABLY GUARANTEES to each Holder,
subject only to the terms of this Policy (which includes each endorsement
hereto), the full and complete payment by the Obligor of Scheduled Payments of
principal of, and interest on, the Obligations.

     For the further protection of each Holder, Financial Security irrevocably
and unconditionally guarantees:

     (a)  payment of the amount of any distribution of principal of, or interest
on, the Obligations made during the Term Of This Policy to such Holder that is
subsequently avoided in whole or in part as a preference payment under
applicable law (such payment to be made by Financial Security in accordance with
Endorsement No. 1 hereto).

     (b)  payment of any amount required to be paid under this Policy by
Financial Security following Financial Security's receipt of notice as described
in Endorsement No. 1 hereto.

     Financial Security shall be subrogated to the rights of each Holder to
receive payments under the Obligations to the extent of any payment by Financial
Security hereunder.

     Except to the extent expressly modified by an endorsement hereto, the
following terms shall have the meanings specified for all purposes of this
Policy.  "Holder" means the registered owner of any Obligation as indicated on
the registration books maintained by or on behalf of the Obligor for such
purpose or, if the Obligation is in bearer form, the holder of the Obligation.
"Scheduled Payments" means payments which are scheduled to be made during the
Term Of This Policy in accordance with the original terms of the Obligations
when issued and without regard to any amendment or modification of such
Obligations thereafter; payments which become due on an accelerated basis as a
result of (a) a default by the Obligor, (b) an election by the Obligor to pay
principal on an accelerated basis or (c) any other cause, shall not constitute
"Scheduled Payments" unless Financial Security shall elect, in its sole
discretion, to pay such principal due upon such acceleration together with any
accrued interest to the date of acceleration.  "Term Of This Policy" shall have
the meaning set forth in Endorsement No. 1 hereto.

     This Policy sets forth in full the undertaking of Financial Security, and
shall not be modified, altered or affected by any other agreement or instrument,
including any modification or amendment thereto, or by the merger, consolidation
or dissolution of the Obligor.  Except to the extent expressly modified by an
endorsement hereto, the premiums paid in respect of this Policy are
nonrefundable for any reason whatsoever, including payment, or provision being
made for payment, of the Obligations prior to maturity.  This Policy may not be
canceled or revoked during the Term Of This Policy.  THIS POLICY IS NOT COVERED
BY THE PROPERTY/CASUALTY INSURANCE SECURITY FUND SPECIFIED IN ARTICLE 76 OF THE
NEW YORK INSURANCE LAW.

In witness whereof, FINANCIAL SECURITY ASSURANCE INC. has caused this Policy to
be executed on its behalf by its Authorized Officer.

                              FINANCIAL SECURITY ASSURANCE INC.

                              By /s/ [Authorized Officer]
                                 ------------------------
                                     Authorized Officer

A subsidiary of Financial Security Assurance Holdings Ltd.
350 Park Avenue, New York N.Y. 10022-6022                        (212) 826-0100
Form 100NY (5/89)
<PAGE>

                               ENDORSEMENT NO. 1

FINANCIAL SECURITY                                               350 Park Avenue
ASSURANCE INC.                                          New York, New York 10022

OBLIGOR:       AmeriCredit Automobile Receivables Trust 2000-A

OBLIGATIONS:   $182,000,000 Class A-1 6.04% Asset Backed Notes
               $313,000,000 Class A-2 6.54% Asset Backed Notes
               $572,000,000 Class A-3 7.15% Asset Backed Notes
               $233,000,000 Class A-4 7.29% Asset Backed Notes

Policy No.: 50902-N
Date of Issuance: February 11, 2000

     1.   Definitions.  For all purposes of this Policy, the terms specified
          -----------
below shall have the meanings or constructions provided below.  Capitalized
terms used herein and not otherwise defined herein shall have the meanings
provided in the Indenture or the Sale and Servicing Agreement unless otherwise
specified.

     "Business Day" means any day other than a Saturday, Sunday, legal holiday
      ------------
or other day on which commercial banking institutions in Wilmington, Delaware,
New York City, New York or Columbus, Ohio or any other location of any successor
Servicer, successor Owner Trustee or successor Trust Collateral Agent are
authorized or obligated by law, executive order or governmental decree to be
closed.

     "Holder" shall have the meaning set forth in the Indenture; provided,
      ------                                                     --------
however Holder shall not include the Obligor or any affiliates or successors
-------
thereof in the event the Obligor, or any such affiliate or successor, is a
registered or beneficial owner of the Obligation.

     "Indenture" means the Indenture, dated as of February 6, 2000 between the
      ---------
Obligor and Bank One, N.A. as Trustee and Trust Collateral Agent, as amended
from time to time with the consent of Financial Security.

     "Indenture Trustee" means Bank One, N.A. in its capacity as Trustee under
      -----------------
the Indenture and any successor in such capacity.

     "Policy" means this Financial Guaranty Insurance Policy and includes each
      ------
endorsement thereto.

     "Receipt" and "Received" mean actual delivery to Financial Security and to
      -------       --------
the Fiscal Agent (as defined below), if any, prior to 12:00 noon, New York City
time, on a
<PAGE>

Business Day; delivery either on a day that is not a Business Day, or after
12:00 noon, New York City time, shall be deemed to be receipt on the next
succeeding Business Day. If any notice or certificate given hereunder by the
Trust Collateral Agent is not in proper form or is not properly completed,
executed or delivered, it shall be deemed not to have been Received, and
Financial Security or its Fiscal Agent shall promptly so advise the Trust
Collateral Agent and the Trust Collateral Agent may submit an amended notice.

     "Sale and Servicing Agreement" means the Sale and Servicing Agreement dated
      ----------------------------
as of February 6, 2000 among the Obligor, AmeriCredit Financial Services, Inc.,
as Servicer, AFS Funding Corp., as Seller and Bank One, N.A., as Backup Servicer
and Trust Collateral Agent, as such agreement may be amended, supplemented or
otherwise modified from time to time in accordance with the terms thereof.

     "Scheduled Payments" means, as to each Insured Distribution Date, payments
      ------------------
which are required to be made to Holders in accordance with the original terms
of the Obligations when issued and without regard to any subsequent amendment or
modification of the Obligations or of the Indenture except amendments or
modifications to which Financial Security has given its prior written consent,
which payments are (i) the Noteholders' Interest Distributable Amount with
respect to the related Distribution Date, (ii) the Noteholders' Remaining Parity
Deficit Amount with respect to the related Distribution Date and (iii) with
respect to the Final Scheduled Distribution Date for any class of Obligations,
the outstanding principal amount of such class on such Final Scheduled
Distribution Date, after taking into account reductions on such Date of such
outstanding principal amount from all sources other than this Policy.  Scheduled
Payments do not include payments which become due on an accelerated basis as a
result of (a) a default by the Obligor, (b) an election by the Obligor to pay
principal on an accelerated basis, (c) the occurrence of an Event of Default
under the Indenture or (d) any other cause, unless Financial Security elects, in
its sole discretion, to pay in whole or in part such principal due upon
acceleration, together with any accrued interest to the date of acceleration.
In the event Financial Security does not so elect, this Policy will continue to
guarantee payment on the Obligations in accordance with their original terms.
Scheduled Payments shall not include (x) any portion of a Noteholders' Interest
Distributable Amount due to Holders because the appropriate notice and
certificate for payment in proper form as required by paragraph 2 hereof was not
timely Received by Financial Security, (y) any portion of a Noteholders'
Interest Distributable Amount due to Holders representing interest on any
Noteholders' Interest Carryover Amount accrued from and including the date of
payment of the amount of such Noteholders' Interest Carryover Amount pursuant
hereto or (z) any Note Prepayment Amounts, unless Financial Security elects, in
its sole discretion, to pay such amount in whole or in part.  Scheduled Payments
shall not include any amounts due in respect of the Obligations attributable to
any increase in interest rate, penalty or other sum payable by the Obligor by
reason of any default or event of default in respect of the Obligations, or by
reason of any deterioration of the credit worthiness of the Obligor, nor shall
Scheduled Payments include, nor shall coverage be provided under this Policy in
respect of, any taxes,

                                       2
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withholding or other charge with respect to any Holder imposed by any
governmental authority due in connection with the payment of any Scheduled
Payment to a Holder.

     "Term Of This Policy" means the period from and including the Date of
      -------------------
Issuance to and including the date on which (i) all Scheduled Payments have been
paid or deemed to be paid within the meaning of Section 4.1 of the Indenture;
(ii) any period during which any Scheduled Payment could have been avoided in
whole or in part as a preference payment under applicable bankruptcy,
insolvency, receivership or similar law shall have expired and (iii) if any
proceedings requisite to avoidance as a preference payment have been commenced
prior to the occurrence of (i) and (ii), a final and nonappealable order in
resolution of each such proceeding has been entered.

     "Trust Collateral Agent" means Bank One, N.A. in its capacity as Trust
      ----------------------
Collateral Agent under the Indenture, acting as agent for the Indenture Trustee
in accordance with the terms of the Indenture, and any successor in such
capacity.

     2.  Notices and Conditions to Payment in Respect of Scheduled Payments.
         ------------------------------------------------------------------
Following Receipt by Financial Security of a notice and certificate from the
Trust Collateral Agent in the form attached as Exhibit A to this Endorsement,
Financial Security will pay any amount payable hereunder in respect of Scheduled
Payments on the Obligations out of the funds of Financial Security on the later
to occur of (a) 12:00 noon, New York City time, on the third Business Day
following such Receipt; and (b) 12:00 noon, New York City time, on the date on
which such payment is due on the Obligations.  Payments due hereunder in respect
of Scheduled Payments will be disbursed to the Trust Collateral Agent by wire
transfer of immediately available funds.

     Financial Security shall be entitled to pay any amount hereunder in respect
of Scheduled Payments on the Obligations, including any amount due on the
Obligations on an accelerated basis, whether or not any notice and certificate
shall have been Received by Financial Security as provided above; provided,
however, that by acceptance of this Policy the Trust Collateral Agent agrees to
provide upon request to Financial Security a notice and certificate in respect
of any such payments made by Financial Security.  Financial Security shall be
entitled to pay hereunder any amount due on the Obligations on an accelerated
basis at any time or from time to time, in whole or in part, prior to the
scheduled date of payment thereof; Scheduled Payments insured hereunder shall
not include interest, in respect of principal paid hereunder on an accelerated
basis, accruing from and after the date of such payment of principal.  Financial
Security's obligations hereunder in respect of Scheduled Payments shall be
discharged to the extent funds are disbursed by Financial Security as provided
herein whether or not such funds are properly applied by the Trust Collateral
Agent.

     3.  Notices and Conditions to Payment in Respect of Scheduled Payments
         ------------------------------------------------------------------
Avoided as Preference Payments.  If any Scheduled Payment is avoided as a
------------------------------
preference payment under applicable bankruptcy, insolvency, receivership or
similar law, Financial Security will pay such amount out of the funds of
Financial Security on the later of (a) the date when due to be paid pursuant to
the Order referred to below or (b) the first to

                                       3
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occur of (i) the fourth Business Day following Receipt by Financial Security
from the Trust Collateral Agent of (A) a certified copy of the order (the
"Order") of the court or other governmental body that exercised jurisdiction to
 ------
the effect that the Holder is required to return Scheduled Payments made with
respect to the Obligations during the Term of this Policy because such payments
were avoidable as preference payments under applicable bankruptcy law, (B) a
certificate of the Holder that the Order has been entered and is not subject to
any stay and (C) an assignment duly executed and delivered by the Holder, in
such form as is reasonably required by Financial Security, and provided to the
Holder by Financial Security, irrevocably assigning to Financial Security all
rights and claims of the Holder relating to or arising under the Obligations
against the estate of the Obligor or otherwise with respect to such preference
payment or (ii) the date of Receipt by Financial Security from the Trust
Collateral Agent of the items referred to in clauses (A), (B) and (C) above if,
at least four Business Days prior to such date of Receipt, Financial Security
shall have Received written notice from the Trust Collateral Agent that such
items were to be delivered on such date and such date was specified in such
notice. Such payment shall be disbursed to the receiver, conservator, debtor-in-
possession or trustee in bankruptcy named in the Order and not to the Trust
Collateral Agent or any Holder directly (unless a Holder has previously paid
such amount to the receiver, conservator, debtor-in-possession or trustee in
bankruptcy named in the Order, in which case such payment shall be disbursed to
the Trust Collateral Agent for distribution to such Holder upon proof of such
payment reasonably satisfactory to Financial Security). In connection with the
foregoing, Financial Security shall have the rights provided pursuant to Section
6.2 of the Sale and Servicing Agreement.

     4.  Governing Law.  This Policy shall be governed by and construed in
         -------------
accordance with the laws of the State of New York without giving effect to the
conflict of laws principles thereof.

     5.  Fiscal Agent.  At any time during the Term of this Policy, Financial
         ------------
Security may appoint a fiscal agent (the "Fiscal Agent") for purposes of this
                                          ------------
Policy by written notice to the Trust Collateral Agent at the notice address
specified in the Indenture specifying the name and notice address of the Fiscal
Agent.  From and after the date of receipt of such notice by the Trust
Collateral Agent, (i) copies of all notices and documents required to be
delivered to Financial Security pursuant to this Policy shall be simultaneously
delivered to the Fiscal Agent and to Financial Security and shall not be deemed
Received until Received by both, and (ii) all payments required to be made by
Financial Security under this Policy may be made directly by Financial Security
or by the Fiscal Agent on behalf of Financial Security.  The Fiscal Agent is the
agent of Financial Security only and the Fiscal Agent shall in no event be
liable to any Holder for any acts of the Fiscal Agent or any failure of
Financial Security to deposit, or cause to be deposited, sufficient funds to
make payments due under the Policy.

     6.  Waiver of Defenses.  To the fullest extent permitted by applicable law,
         ------------------
Financial Security agrees not to assert, and hereby waives, for the benefit of
each Holder, all rights (whether by counterclaim, setoff or otherwise) and
defenses (including, without limitation, the defense of fraud), whether acquired
by subrogation, assignment or

                                       4
<PAGE>

otherwise, to the extent that such rights and defenses may be available to
Financial Security to avoid payment of its obligations under this Policy in
accordance with the express provisions of this Policy.

     7.   Notices. All notices to be given hereunder shall be in writing (except
          -------
as otherwise specifically provided herein) and shall be mailed by registered
mail or personally delivered or telecopied to Financial Security as follows:

          Financial Security Assurance Inc.
          350 Park Avenue
          New York, NY 10022
          Attention: Senior Vice President - Transaction Oversight Department
          Telecopy No.: (212) 339-3518
          Confirmation: (212) 826-0100

     Financial Security may specify a different address or addresses by writing
mailed or delivered to the Trust Collateral Agent.

     8.   Priorities.  In the event that any term or provision of the face of
          ----------
this Policy is inconsistent with the provisions of this Endorsement, the
provisions of this Endorsement shall take precedence and shall be binding.

     9.   Exclusions From Insurance Guaranty Funds.  This Policy is not covered
          ----------------------------------------
by the Property/Casualty Insurance Security Fund specified in Article 76 of the
New York Insurance Law.  This Policy is not covered by the Florida Insurance
Guaranty Association created under Part II of Chapter 631 of the Florida
Insurance Code.  In the event that Financial Security were to become insolvent,
any claims arising under this Policy are excluded from coverage by the
California Insurance Guaranty Association, established pursuant to Article 14.2
of Chapter 1 of Part 2 of Division 1 of the California Insurance Code.

     10.  Surrender of Policy.  The Trust Collateral Agent shall surrender this
          -------------------
Policy to Financial Security for cancellation upon expiration of the Term of
this Policy.

     IN WITNESS WHEREOF, FINANCIAL SECURITY ASSURANCE INC. has caused this
Endorsement No. 1 to be executed by its Authorized Officer.

                         FINANCIAL SECURITY ASSURANCE INC.

                         By: /s/ [Authorized Officer]
                             -------------------------
                                    Authorized Officer

                                       5
<PAGE>

                                   EXHIBIT A

                             To Endorsement No. 1

                        NOTICE OF CLAIM AND CERTIFICATE

                    (Letterhead of Trust Collateral Agent)

Financial Security Assurance Inc.
350 Park Avenue
New York, NY 10022

     Re:  AmeriCredit Automobile Receivables Trust 2000-A
          -----------------------------------------------

     The undersigned, a duly authorized officer of Bank One, N.A. (the "Trust
Collateral Agent"), hereby certifies to Financial Security Assurance Inc.
("Financial Security"), with reference to Financial Guaranty Insurance Policy
No. 50902-N dated February 11, 2000 (the "Policy") issued by Financial Security
in respect of the $182,000,000 Class A-1 6.04% Asset Backed Notes, $313,000,000
Class A-2 6.54% Asset Backed Notes, $572,000,000 Class A-3 7.15% Asset Backed
Notes and $233,000,000 Class A-4 7.29% Asset Backed Notes of the above-
referenced Trust (the "Obligations"), that:

     (i)    The Trust Collateral Agent is the Trust Collateral Agent under the
Indenture.

     (ii)   The sum of all amounts on deposit (or scheduled to be on deposit) in
the Note Distribution Account and available for distribution to the Holders
pursuant to the Indenture will be $_________ (the "Shortfall") less than the
aggregate amount of Scheduled Payments due on ___________________.

     (iii)  The Trust Collateral Agent is making a claim under the Policy for
the Shortfall to be applied to the payment of Scheduled Payments.

     (iv)   The Trust Collateral Agent agrees that, following receipt of funds
from Financial Security, it shall (a) hold such amounts in trust and apply the
same directly to the payment of Scheduled Payments on the Obligations when due;
(b) not apply such funds for any other purpose; (c) not commingle such funds
with other funds held by the Trust Collateral Agent and (d) maintain an accurate
record of such payments with respect to each Obligation and the corresponding
claim on the Policy and proceeds thereof, and, if the Obligation is required to
be surrendered or presented for such payment, shall stamp on each such
Obligation the legend "$[insert applicable amount] paid by Financial Security
and the balance hereof has been cancelled and reissued" and then shall deliver
such Obligation to Financial Security.

                                      A-1
<PAGE>

     (v)    The Trust Collateral Agent, on behalf of the Holders, hereby assigns
to Financial Security the rights of the Holders with respect to the Obligations
to the extent of any payments under the Policy, including, without limitation,
any amounts due to the Holders in respect of securities law violations arising
from the offer and sale of the Obligations. The foregoing assignment is in
addition to, and not in limitation of, rights of subrogation otherwise available
to Financial Security in respect of such payments. Payments to Financial
Security in respect of the foregoing assignment shall in all cases be subject to
and subordinate to the rights of the Holders to receive all Scheduled Payments
in respect of the Obligations. The Trust Collateral Agent shall take such action
and deliver such instruments as may be reasonably requested or required by
Financial Security to effectuate the purpose or provisions of this clause (v).

     (vi)   The Trust Collateral Agent, on behalf of the Holders, hereby
appoints Financial Security as agent and attorney-in-fact for the Trust
Collateral Agent and each such Holder in any legal proceeding with respect to
the Obligations. The Trust Collateral Agent hereby agrees that, so long as an
Insurer Default (as defined in the Indenture) shall not exist, Financial
Security may at any time during the continuation of any proceeding by or against
the Obligor under the United States Bankruptcy Code or any other applicable
bankruptcy, insolvency, receivership, rehabilitation or similar law (an
"Insolvency Proceeding") direct all matters relating to such Insolvency
Proceeding, including without limitation, (A) all matters relating to any claim
in connection with an Insolvency Proceeding seeking the avoidance as a
preferential transfer of any payment made with respect to the Obligations (a
"Preference Claim"), (B) the direction of any appeal of any order relating to
any Preference Claim at the expense of Financial Security but subject to
reimbursement as provided in the Insurance Agreement and (C) the posting of any
surety, supersedes or performance bond pending any such appeal. In addition, the
Trust Collateral Agent hereby agrees that Financial Security shall be subrogated
to, and the Trust Collateral Agent on its behalf and on behalf of each Holder,
hereby delegates and assigns, to the fullest extent permitted by law, the rights
of the Trust Collateral Agent and each Holder in the conduct of any Insolvency
Proceeding, including, without limitation, all rights of any party to an
adversary proceeding or action with respect to any court order issued in
connection with any such Insolvency Proceeding.

     (vii)  Payment should be made by wire transfer directed to [SPECIFY
ACCOUNT].

     Unless the context otherwise requires, capitalized terms used in this
Notice of Claim and Certificate and not defined herein shall have the meanings
provided in the Policy.

                                      A-2
<PAGE>

     IN WITNESS WHEREOF, the Trust Collateral Agent has executed and delivered
this Notice of Claim and Certificate as of the __th day of ________, 20___.

                              BANK ONE, N.A.
                              as Trust Collateral Agent

                              By____________________________
                              Title_________________________


__________________________________________________

For Financial Security or Fiscal Agent Use Only

Wire transfer sent on ____________ By ___________________________
Confirmation Number _____________________.

                                      A-3