http://consumerist.com/2009/09/09/car-dealers-can-use/

“An auto dealership checking a consumer’s credit through TransUnion is not required to have the individual’s social security number (SSN) in order to submit the request,” says Steven Katz, a TU spokesman. Does the dealer need your permission to do that? “The dealer does not need ‘permission'; rather, it needs only certify a permissible purpose (such as extension of credit),” says Katz. [Consumer Reports]