I have a TH350 in an 86 Camaro that was rebuilt about a year ago when I was rebuilding the engine. I have about 500 miles on it now. The other day I was driving along with it locked in second gear and it wouldn't shift to third. When I got home I realized that it wouldn't go into reverse or neutral. I checked the linkage and it is hooked up and working. It will go into Park, kinda. What ever engages in Park to lock the transmission engages, but it is still in gear. It will sit there idling rocking the car back and forth. Pull it out of park and it acts just like it is locked in second gear, regardless of what gear I put the shifter in. Takes off in first, shifts into second and stays there. I can run it up to about 60 mph and let off of the gas and it acts like a false neutral, the rpm's will drop almost to idle. If I floor it then it will grab when the rpm's get up to where they should be in that gear. Fluid is full and not burned. Any ideas or input would be greatly appreciated.
Thanks.

 

Pull the pan off and see if there are any parts lying in the bottom before we start guessing as to what's wrong.