l took the car in for the ''free computer check'' and they called and told me the computer codes indicated they needed to remove the tranny to ''see'' what is going on. The cost on that was $495. l said OK. they called back to say the total repair would be $3400 - l said ''no way'' and they reduced the price to $2295, and l said I'd get back to them.
next thing l know they did the work and wanna get paid, and they have my car.
What are my rights, and what is fair?

It depends on what u signed when u brought the car in. If u did not sign anything authorizing the work, they should not have done it. If l were you, I'd take to the Better Business Bureau, the Chamber of Commerce, & the State Attorney General as a start. Is there a consumer protection agency where u live? File complaints with everybody u can think of. Do not yell & rank. Be polite to everybody. Just tell them ur story & that u did not authorize the repairs. It would might pay to get an attorney. This sounds like a real racket. There was probably nothing wrong with the tranny in the first place. Unfortunately, u now know how they make money on these ''free'' checks.

in the state of illinois, the total bill should not be more than 10% of the quoted repairs. You r legally required to pay the $495 since u authorized it. You r not legally required to pay the additional cost. The repair facility has no rights here, u may pick up the vehicle, they may fight u for payment, but u r not liable for it, if they do not release the vehicle, contact the police, as they r holding ur property. Make sure there is not a mechanics lein put on the vehicle. This is illegal if they do.