My friend is telling me that when you engine over heats that it will cause the transmission to go bad also. I have never heard of that is this true. I don't see how one would affect the other if so please explain.

 

Well it would probably take quite a few miles of the engine overheating to ruin an automatic trans.You have to remember that in the radiator is were the trans cooler is and if you are driving an overheated car for long enough the trans fluid also gets very hot..............not good for a auto trans.

 

The engine is bolted to tranny and transfers heat thru the housing's dozens or so bolts.............when the block gets to 300F so does tranny housing by then everything is done.............cooked.

The radiator heat exchanger is designed to heat the ATF [up faster] in winter not cool it much in summer as both are running at 174-212F.

 

sounds feasible but it's not a black-and-white answer IMO.