I think buyer has a case if he can prove that the seller knew about the transmission problem and covered it up. Basically if the seller did not disclosure the transmission problem and sold the car under false pretense, then the buyer can recover damages.
If the buyer can not prove the seller knew about the transmission problem, then the buyer can not ask for damages. If the seller really did not know about the problem and sold the car as is, why should the seller be liable for problems that he had no control over? After all, the car did not have a warrantee and was sold as is.
It is responsibility of the buyer to prove the seller knew about the problem and tried to cover it up. In a civil court, the plaintiff (buyer) will have to prove that the preponderance of the evidence shows the seller covered up the problem.
The buyer needs to go to a transmission shop and have an expert diagnose the problem. If the expert is willing to testify that the transmission problem was covered up, then the buyer has a good case. If the buyer can not get an expert to testify that the transmission problem was covered up, then it will be very difficult to prove with preponderance of the evidence that the seller sold the car without disclosing the transmission problem.
Either way, the first step the buyer needs to do is to take the car to an automatic transmission shop with a good reputation.
