1985 Pontiac Bonneville
5.0 Engine

This past weekend I had some radiator problems causing my car to overheat. I had to drive it a few times with it overheating. The max temp got up to about 255. I had to replace the radiator and thermostat. Once I had that all fixed I noticed I had no reverse. I figured since I drove the car with it overheating it may have burnt up some tranny fluid. I was right and she was about a pint low. I filled the fluid to the proper level and still have no reverse. Now I'm guessing the overheating caused some damage in the tranny causing the reverse to go out. What can be wrong besides low fluid? What kind of damage can overheating cause to a tranny? Am I looking at my whole tranny going out and costly repairs? Any tranny experts on here that can give some advice I would really appreciate it. Or if anybody else has experienced this same problem. Thanks.

I would start with a tranny flush and new fluid, add some Lucas tranny guard and see if reverse comes back?
If not its off to the tranny shop.

Yeah, automatic transmissions are very sensative to heat. Heat will actually kill an auto trans as quick or quicker then just about anything else. Not sure if the overheating actually caused the no reverse problem, but I am sure it didn't help.

Is it the three speed trans, if so, probably the TH350, and about $800 - $1,000 to rebuild at a trans shop, depending on your location.

I agree to start with a flush and filter change and see what happens. Worst case is you spend $30 and it doesn't work :? Sure, it is $30 and might help at all, but it might also fix the problem and help avoid costly repairs.

Was there any signs of reverse going out before this? Was it slow to shift into any gear, or slow to go into reverse when cold or hot?