I have an 87 5.7 (TPI) GTA, with a 700-R4.

On extremely heavy escalation the transmission sounds like it is hitting the floor of the car. It is a loud knocking sound; the transmission almost feels like it is hopping up and down.

The cross member is tight and the transmission mount is bran new, the motor mounts are new, and the u-joints are all good. I’m starting to think maybe it is the guts of the transmission bouncing around or the converter failing. Has anyone had this problem or have any Ideas what this might be.

I am running the car without the lock-up converter connected, not sure if this has anything to do with it or not?
I also just swaped this motor and transmission in and used the Painless wiring harness and buypassed the VSS.

If you have your foot to the floor, it also will not shift unless you let off a bit.

 

When you replaced the tranny mount did you use a rubber or did you use a poly mount? if you just replaced it with a rubber mount you might want to double check it cause its not to hard to break those things. and from what it sounds like with the way you drive, you probably already broke it.

 

Or a loose exhaust pipe is bumping on the floor boards......

or torque arm mount is busted....

 

have you tried getting under your car and loking things over? might find a broke mount of some sort like was said above.

 

I figured out what was making it hop, I should have noticed it before. The front drive shaft yoke was hitting a bracket. Feel stupid for posting that now. Thanks for the help though.
The other thing is the transmission will not shift into the next gear under full throttle unless I let off of the gas for a second or so. Is this a common problem? Any suggestions on this would be appreciated also.

 

adjust the TV cable

 

Ok, I'll try and not sound too stupid, but doesn't the kick down cable only adjust the kick down speed?

I thought the changing of the gears was determined by the vacuum module

She kicks down really nice, no problem in the down shifts, only on the way up.