I was behind a newer Pontiac Grand Am when one of my dogs started to become sick and I let me foot off the brake a little when I turned around to look at the dog. I have a Honda Fit and I bumped the grand am in front of me, but when we got out of our cars neither of us could find any damage to either car, not even a scratch. I felt we didn’t need to do anything else because both cars were fine but the other car’s passenger kept insisting that the bump might have damaged the tranny in the trans am. Could a very low impact bump (less than 5mph) damage a transmission? It took forever to convince the passenger that the car was fine.
There’s always a possibility of anything happening, but the chances of a less than 5 MPH impact harming the transmission on that car are about as close to zero as you can get.
If you whacked them at 35 MPH then maybe? they might have a case; and that’s a slim maybe also.
So the owner of the Grand Am momentarily forgot that his/her mechanic had said that the car’s tranny was on the verge of failure only last week. The passenger, not being shaken by the accident, remembered, and figured YOU would make a fantastic scapegoat. Fear not. You didn’t hurt the transmission in a lowe speed rear impact of a FWD car. I recently wrecked out a '99 Taurus that was hit so hard from behind that the trunk wall was pushed almost up to the back of the front seat. It was quite a wreck. That 61K mile AX4N transmission is now propelling a '99 Sable, and it’s just fine. Need a good '99 Taurusable engine? I have one left over. Those, and the hood were all that was any good.
From what you have posted, you didnt hurt their transmission at all. Watch out for knuckleheads like this, it sounds like they are trying to get a free transmission out of this. I’m surprised no one grabbed their neck…