I was hearing a 'clunk' when I put my 87 IROC 700R-4 in reverse, so I decided to replace the transmission mount. I searched this forum for installation tips and found several posts on the subject and ordered a new Energy Suspension polyurethane mount from Summit.

Some of the posts I found talked about whether or not to install the plate (comes with the mount) designed to fit between the transmission and mount. The installation instructions that come with the mount say to put it in, it's not an option. After doing this, I noticed the car vibrated much more than with the stock mount. The stock mount was not broken, but worn. The vibration was not caused by an unbalanced driveshaft, as the vibrations could be felt while stopped.

So, I decided to take the plate out. The car now feels like it did with the stock mount, very little vibration. The original problem remains however, I still hear the 'clunk' when putting the car in reverse.

I'm wondering now if the sound really indicates a problem that needs attention or is just characteristic of the transmission. I visually inspected the U joints while changing the mount and they didn't look worn. Anything else to look for before I take it to a transmission shop? Thanks.

 

I dont know about the clucking but i put the plate in and put spacers between the frame and tranny x member.