Yes, you have a case against the towing company and a readily provable tort case of negligence. But not necessarily so if your husband should attempt to present it pro se.
The previous responses seem to have overlooked the salient fact that the principles and laws of bailment govern the circumstances here. We're not talking about a stranger that is alleged to have negligently caused damage to the car. There the claimant has the burden of proving negligence on the part of the alleged wrongdoer. But here we are taking about the special relationship of a bailor and bailee and the burden of proving liability greatly differs.
A bailment is created when the owner of personal property places it temporarily in the possession and control of a third party for a specific and agreed purpose. (Like taking your clothing to a commercial dry cleaner.)
And because this involves bailment law, your husband DOES NOT have to prove that the towing company was at fault!
If the case is properly prepared and presented,
The towing company MUST PROVE that the damaged transmission was NOT the result of their failure to exercise ordinary care in transporting and storing the vehicle.
It makes no difference that the police and not your husband engaged the towing company to remove the car. If it had broken down and he had called the towing company, it would be an “express or contract of bailment”. But it is a bailment nevertheless and one known as a CONSTRUCTIVE BAILMENT. Your husband the bailor and the towing company the bailee.
And because the company charged your husband for the towing it was not a gratuitous bailment. It was a bailment of mutual benefit making it incumbent upon the towing company to exercise ordinary care in protecting the transmission from being damaged. The same degree of care it would exercise with its own equipment.
In the lawsuit all your husband needs to show to make a prima facie case for recovery of the cost of repairs is to prove that the transmission was in good working order before the towing and that it was only discovered damaged when the vehicle was returned to him.
It had to be in good working order, at least to the extent that it would start and the transmission shifted through the gears as designed, or he wouldn’t have been on the highway. And all he has to do is to testify as to those facts.
Once those facts are in the court record, plus competent evidence of the cost of repairs, the burden of proof then shifts to the towing company to prove convincingly that it exercised ordinary care in protecting against damage to the transmission.
But if you expect to come out on top you are going to need an experienced trial lawyer.
