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                                                                    EXHIBIT 10.8

                                                                  EXECUTION COPY

                                 AMENDMENT NO. 1

                          dated as of December 1, 2002

                                      among

                      AMERICREDIT MTN RECEIVABLES TRUST II,

                                   as Debtor,

                      AMERICREDIT FINANCIAL SERVICES, INC.,
                          Individually and as Servicer,

                           MBIA INSURANCE CORPORATION,
                                   as Insurer

                                       and

                         MERIDIAN FUNDING COMPANY, LLC,
                                  as Purchaser

                                       to

                               SECURITY AGREEMENT

                            dated as of June 12 ,2001

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          AMENDMENT NO. 1, dated as of December 1, 2002 (the "Amendment"), among
AMERICREDIT MTN RECEIVABLES TRUST II (the "Debtor"), AMERICREDIT FINANCIAL
SERVICES, INC., individually and in its capacity as Servicer ("AFS"), MBIA
INSURANCE CORPORATION, as Insurer ("MBIA"), and MERIDIAN FUNDING COMPANY, LLC,
as Purchaser ("Meridian"), to the Security Agreement dated as of June 12, 2001
(the "Security Agreement"), among the Debtor, AFS, AmeriCredit MTN Corp. II and
The Chase Manhattan Bank (predecessor to JPMorgan Chase Bank), as Collateral
Agent and as Securities Intermediary.

          WHEREAS, Section 9.2(b) of the Security Agreement permits amendment of
the Security Agreement by the Debtor, AFS, MBIA and Meridian (the "Parties")
upon the terms and conditions specified therein;

          WHEREAS, the Parties wish to amend the Security Agreement.

          NOW, THEREFORE, the Parties agree that the Security Agreement is
hereby amended effective as of the date hereof as follows:

     Section 1. Definitions. Each term used but not defined herein shall have
the meaning assigned to such term in the Security Agreement.

     Section 2. Amendment to Section 1.1 (Certain Defined Terms).

          (a)    The definition of "Adjusted EBITDA" is deleted in its entirety.

          (b)    The following definitions are inserted in Section 1.1 in
appropriate alphabetical order:

                 "EBITDA" means, with respect to AmeriCredit Corp., GAAP
     earnings before interest, taxes, depreciation and amortization.

                 "Ineligible Receivable" means any Receivable that is not an
     Eligible Receivable.

                 "Substitute Receivables Pool" means, on any Delivery Date, that
     portion of the Receivables comprising the Receivables Delivery having an
     Aggregate Outstanding Balance equal to the Aggregate Outstanding Balance of
     those Receivables that have become Ineligible Receivables since the most
     recent to occur of (i) the most recent preceding Delivery Date, (ii) the
     most recent preceding Take-Out Date and (iii) the most recent preceding
     Determination Date.

     Section 3. Amendment to Section 2.11 (Funding Account). Clause (i) of
Subsection 2.11(c) is amended by replacing the phrase "(y) the aggregate Net
Receivable Balance of all Receivables comprising the Receivables Delivery, but
in no event" contained therein with "(y) the Aggregate Outstanding Balance of
all Receivables comprising the Receivables Delivery less the Aggregate
Outstanding Balance of all Receivables comprising the Substitute Receivables
Pool, but in no event (1) an amount less than zero or (2)".

                                        1

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     Section 4. Amendments to Section 6.1 (Termination and Amortization Events).

          (a)    Clause (x) of Section 6.1 is deleted in its entirety and
replaced with the following:

                 (x)    the Tangible Net Worth of AmeriCredit Corp. shall be
     less than the sum of (a) $1,800,000,000 and (b) 75% of the cumulative
     positive net income (without deduction for negative net income) of
     AmeriCredit Corp. for each fiscal quarter having been completed since
     September 30, 2002, as reported in each annual report on Form 10-K and
     periodic report on Form 10-Q filed by AmeriCredit Corp. with the Securities
     and Exchange Commission; or

          (b)    Clause (z) of Section 6.1 is deleted in its entirety and
replaced with the following:

                 (z)    the ratio of AmeriCredit Corp.'s EBITDA (plus any loss
     provision minus net charge-offs) for the financial quarter ended December
     31, 2002 to its Interest Expense for the financial quarter ended December
     31, 2002 shall be less than 1.5x. The ratio of AmeriCredit Corp.'s EBITDA
     (plus any loss provision minus net charge-offs) for the financial quarter
     ended March 31, 2003 to its Interest Expense for the financial quarter
     ended March 31, 2003 shall be less than 1.8x. The average of the ratios of
     AmeriCredit Corp.'s EBITDA to Interest Expense for the two most recent
     financial quarters ended June 30, 2003 shall be less than l.0x. The average
     of the ratios of AmeriCredit Corp.'s EBITDA to Interest Expense for the two
     most recent financial quarters ended September 30, 2003 or December 31,
     2003 shall be less than 1.1x. The average of the ratios of AmeriCredit
     Corp.'s EBITDA to Interest Expense for the two most recent financial
     quarters ended March 31, 2004 and any two consecutive financial quarters
     thereafter shall be less than 1.2x; or

          (c)    Clause (jj) of Section 6.1 is deleted in its entirety and
replaced with the following:

                 (jj)   more than 30% of the Eligible Receivables held as
     Collateral have Contracts which provide for 72 monthly payments and such
     condition shall continue for five Business Days; or

     Section 5. Amendment to Exhibit M (Cumulative Net Loss Table). The entry of
"0.50%" in the "Trigger Rate" column, corresponding to a "Seasoning in Months"
of "3", is deleted and replaced with "1.25%".

     Section 6. Counterparts. This Amendment to the Security Agreement may be
executed in several counterparts, each of which shall be deemed an original
hereof and all of which, when taken together, shall constitute one and the same
Amendment to the Security Agreement.

                                        2

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     Section 7. Ratification of Security Agreement. Except as provided herein,
all provisions, terms and conditions of the Security Agreement shall remain in
full force and effect. As amended hereby, the Security Agreement is ratified and
confirmed in all respects.

     Section 8. Entire Agreement. This Amendment sets forth the entire agreement
between the Parties with respect to the subject matter hereof, and this
Amendment supersedes and replaces any agreement or understanding that may have
existed between the Parties prior to the date hereof in respect of such subject
matter.

                                        3

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          IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the date set forth on the first page hereof.


                                AMERICREDIT MTN RECEIVABLES TRUST II

                                By: DEUTSCHE BANK TRUST COMPANY
                                 DELAWARE, not in its individual capacity but
                                 solely as Owner Trustee on behalf of the Issuer

                                By:               /s/ LOUIS BODI
                                   ---------------------------------------------
                                                                ATTORNEY-IN-FACT
                                   Name:             LOUIS BODI
                                   Title:          VICE PRESIDENT


                                AMERICREDIT FINANCIAL SERVICES, INC.,
                                 Individually and as Servicer,

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:


                                MBIA INSURANCE CORPORATION,
                                 as Insurer,

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:


                                MERIDIAN FUNDING COMPANY, LLC,
                                 as Purchaser

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:

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          IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the date set forth on the first page hereof.


                                AMERICREDIT MTN RECEIVABLES TRUST II

                                By: DEUTSCHE BANK TRUST COMPANY
                                 DELAWARE, not in its individual capacity but
                                 solely as Owner Trustee on behalf of the Issuer

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:


                                AMERICREDIT FINANCIAL SERVICES, INC.,
                                 Individually and as Servicer,

                                By: /s/ Beth Sorensen
                                   ---------------------------------------------
                                   Name:  Beth Sorensen
                                   Title: Senior Vice President, Finance


                                MBIA INSURANCE CORPORATION,
                                 as Insurer,

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:


                                MERIDIAN FUNDING COMPANY, LLC,
                                 as Purchaser

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:

<PAGE>

          IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the date set forth on the first page hereof.


                                AMERICREDIT MTN RECEIVABLES TRUST II

                                By: DEUTSCHE BANK TRUST COMPANY
                                 DELAWARE, not in its individual capacity but
                                 solely as Owner Trustee on behalf of the Issuer

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:


                                AMERICREDIT FINANCIAL SERVICES, INC.,
                                 Individually and as Servicer,

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:


                                MBIA INSURANCE CORPORATION,
                                 as Insurer,

                                By: /s/ Rosemary Kelley
                                   -------------------------------------------
                                   Name:  Rosemary Kelley
                                   Title: Director


                                MERIDIAN FUNDING COMPANY, LLC,
                                 as Purchaser

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:

<PAGE>

          IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the date set forth on the first page hereof.


                                AMERICREDIT MTN RECEIVABLES TRUST II

                                By: DEUTSCHE BANK TRUST COMPANY
                                 DELAWARE, not in its individual capacity but
                                 solely as Owner Trustee on behalf of the Issuer

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:


                                AMERICREDIT FINANCIAL SERVICES, INC.,
                                 Individually and as Servicer,

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:


                                MBIA INSURANCE CORPORATION,
                                 as Insurer,

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:


                                MERIDIAN FUNDING COMPANY. LLC,
                                 as Purchaser

                                By:          /s/ Andrew L. Stidd
                                   ---------------------------------------------
                                   Name:       Andrew L. Stidd
                                   Title:         President