Consider refinancing your existing vehicle loan or lease through AutoLoanSoup
The following is an excellent source for auto loans for people with an "Excellent" to "Less Then Peerfect" Credit Rating: AutoLoanSolutions
Here are several excellent car loan sources for people who have a "Poor" to "Bad" Credit Rating: AutoLoanSoup
The lenders above specialize in helping individuals obtain bad credit auto loans for the purchase of a new or used vehicle. Apply to them and compare. You're under no obligation to accept any of their offers.
Also visit my new website GreatCreditCardDeals.com to apply for a credit card. If managed properly it could eventually improve your credit rating.
If you're not sure what your credit rating is go to CreditReport.com.