<PAGE>

Exhibit 99.4

[Ernst & Young, LLP Letterhead]

             Report of Independent Registered Public Accounting Firm

USAA Federal Savings Bank
Wachovia Trust Company, National Association
JPMorgan Chase Bank

We have examined management's assertion, included in the accompanying Management
Assertion, that USAA Federal Savings Bank "the Bank" complied with Article III,
Section 3.9 of the Sale and Servicing Agreement, dated as of November 1, 2005
"the Agreement," between USAA Federal Savings Bank as Seller and Servicer, and
the USAA Auto Owner Trust 2005-4 as Issuer, with Wachovia Trust Company,
National Association, as Owner Trustee, and JPMorgan Chase Bank as Indenture
Trustee, for the year ended December 31, 2005. Management is responsible for the
Bank's compliance with Article III, Section 3.9 of the Agreement, including the
accuracy of the mathematical calculations of each amount set forth in the
Monthly Servicer Certificates, delivered pursuant to Article III, Section 3.9,
using the Bank's computer reports which were the source of such amounts. Our
responsibility is to express an opinion on management's assertion about the
Bank's compliance based on our examination.

Our examination was conducted in accordance with attestation standards
established by the Public Company Accounting Oversight Board and, accordingly,
included examining, on a test basis, evidence about the Bank's compliance with
the aforementioned section of the Agreement and performing such other procedures
as we considered necessary in the circumstances. We believe that our examination
provides a reasonable basis for our opinion. Our examination does not provide a
legal determination on the Bank's compliance with that section.

In our opinion, management's assertion that the Bank complied with the
aforementioned section of the Agreement during the year ended December 31, 2005,
is fairly stated, in all material respects.

                                                           /s/ ERNST & YOUNG LLP

February 17, 2006





<PAGE>

Exhibit 99.4 Continued

[USAA Federal Savings Bank letterhead]

                              Management Assertion

February 17, 2006

The management of USAA Federal Savings Bank (the "Bank") is responsible for the
preparation of Monthly Servicer Certificates in compliance with Article III,
Section 3.9 of the Sale and Servicing Agreement, dated as of November 1, 2005
(the "Agreement"), between USAA Federal Savings Bank, as Seller and Servicer,
USAA Acceptance, LLC, as Depositor, and the USAA Auto Owner Trust 2005-4, as
Issuer, with Wachovia Trust Company, National Association, as Owner Trustee, and
JP Morgan Chase Bank, as Indenture Trustee. Management is also responsible for
the accuracy of the mathematical calculations of each amount set forth in the
Monthly Servicer Certificates, delivered pursuant to Article III, Section 3.9 of
the Agreement, using the Bank's computer reports which were the source of such
amounts.

Management has performed an evaluation of the Bank's compliance with Article
III, Section 3.9 of the Agreement, including the accuracy of the related
mathematical calculations, for the year ended December 31, 2005. Based on this
evaluation, management believes that, for the year ended December 31, 2005, the
Bank was materially in compliance with Article III, Section 3.9 of the
Agreement, including the related mathematical calculations.

/s/ EDWIN T. MCQUISTON
-----------------------
Edwin T. McQuiston
SVP - Corporate Finance





<PAGE>

Exhibit 99.4 Continued

[Ernst & Young, LLP letterhead]

             Report of Independent Registered Public Accounting Firm

USAA Federal Savings Bank
Wachovia Trust Company, National Association
JPMorgan Chase Bank

We have examined management's assertion, included in the accompanying Management
Assertion, that USAA Federal Savings Bank "the Bank" complied with the servicing
requirements in Article III, Sections 3.1, 3.2, 3.3, 3.4, 3.5, and 3.14 of the
Sale and Servicing Agreement, dated as of November 1, 2005 "the Agreement,"
between USAA Federal Savings Bank as Seller and Servicer, and the USAA Auto
Owner Trust 2005-4 as Issuer, with Wachovia Trust Company, National Association,
as Owner Trustee, and JPMorgan Chase Bank as Indenture Trustee, for the year
ended December 31, 2005. Management is responsible for the Bank's compliance
with those requirements. Our responsibility is to express an opinion on
management's assertion about the Bank's compliance based on our examination.

Our examination was conducted in accordance with attestation standards
established by the Public Company Accounting Oversight Board and, accordingly,
included examining, on a test basis, evidence about the Bank's compliance with
the aforementioned sections of the Agreement and performing such other
procedures as we considered necessary in the circumstances. We believe that our
examination provides a reasonable basis for our opinion. Our examination does
not provide a legal determination on the Bank's compliance with those sections.

In our opinion, management's assertion that the Bank complied with the
aforementioned sections of the Agreement during the year ended December 31,
2005, is fairly stated, in all material respects.

                                                               ERNST & YOUNG LLP

February 17, 2006





<PAGE>

Exhibit 99.4 Continued

[USAA Federal Savings Bank letterhead]

                              Management Assertion

February 17, 2006

The management of USAA Federal Savings Bank (the "Bank") is responsible for
complying with the servicing requirements of Article III, Sections 3.1, 3.2,
3.3, 3.4, 3.5, and 3.14 of the Sale and Servicing Agreement, dated as of
November 1, 2005 (the "Agreement"), between USAA Federal Savings Bank, as Seller
and Servicer, USAA Acceptance, LLC, as Depositor, and the USAA Auto Owner Trust
2005-4, as Issuer, with Wachovia Trust Company, National Association, as Owner
Trustee, and JP Morgan Chase Bank, as Indenture Trustee.

Management has performed an evaluation of the Bank's compliance with the
aforementioned sections of the Agreement for the year ended December 31, 2005.
Based on this evaluation, management believes that, for the year ended December
31, 2005, the Bank was materially in compliance with the aforementioned sections
of the Agreement.

/s/ MICHAEL A. LUBY
---------------------------
Michael A. Luby
President and CEO

/s/ FRITZ D. BOHNE
---------------------------
Fritz D. Bohne
VP Senior Financial Officer