EXHIBIT 31

CERTIFICATION PURSUANT TO

Rule 15d-14(d)

I, Edwin T.
McQuiston, certify that:

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| | -- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | 1. | I have
 reviewed this report on Form 10-K and all reports on Form 10-D required to be
 filed in respect of the period covered by this report on Form 10-K of USAA
 Auto Owner Trust 2008-3 (the Exchange Act periodic reports);                                                                                                                                                                                                                                                                                                                                               
| |    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
| | 2. | Based on my
 knowledge, the Exchange Act periodic reports, taken as a whole, do not
 contain any untrue statement of a material fact or omit to state a material
 fact necessary to make the statements made, in light of the circumstances
 under which such statements were made, not misleading with respect to the
 period covered by this report;                                                                                                                                                                                                                          
| |    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
| | 3. | Based on my
 knowledge, all of the distribution, servicing and other information required
 to be provided under Form 10-D for the period covered by this report is
 included in the Exchange Act periodic reports;                                                                                                                                                                                                                                                                                                                                                              
| |    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
| | 4. | I am
 responsible for reviewing the activities performed by the servicer and based
 on my knowledge and the compliance review conducted in preparing the servicer
 compliance statement required in this report under Item 1123 of Regulation
 AB, and except as disclosed in the Exchange Act periodic reports, the
 servicer has fulfilled its obligations under the servicing agreement in all
 material respects; and                                                                                                                                                       
| |    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
| | 5. | All of the
 reports on assessment of compliance with servicing criteria for asset-backed
 securities and their related attestation reports on assessment of compliance
 with servicing criteria for asset-backed securities required to be included
 in this report in accordance with Item 1122 of Regulation AB and Exchange Act
 Rules 13a-18 and 15d-18 have been included as an exhibit to this report,
 except as otherwise disclosed in this report. Any material instances of
 noncompliance described in such reports have been disclosed in this report on
 Form 10-K.

In giving the
certifications above, I have reasonably relied on information provided to me by
the following unaffiliated parties: The Bank of New York Mellon; FDI Computer
Consulting, Inc.

|                |                                                      
|--------------- | -----------------------------------------------------
|                | /s/ EDWIN T.
 MCQUISTON                              
|                |                                                      
|                | Name: Edwin
 T. McQuiston                            
|                | Title:
 Senior Vice President, Treasurer             
|                | (Senior
 Officer in Charge of the Servicing Function)
|                |                                                      
|March 31,
 2009 |                                                      

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