March 24, 2008, TCRA Email Forum
We have a converter from 06 pontiac gran prix 5.3 8cylinder. the tcc piston is bent like to much apply pressure or weak piston . anyone have any experience with this?. It is a gm rebuilt trans & converter.I have seen this same piston deflection 1 time before and it was another converter that did not have a 4 digit code like this one. I have posted pictures at http://www.flickr.com. (search people) fnatrans and you will find 2 pics
We had one of these in the shop last week, same problem. GM should have used the 4T80E in this car, probably good for us they didn’t. It is my understanding that something is wrong in the transmission valve body and causes high line pressure on the lock up piston. Sonnax has numerous valves fixes for this transmission and I even had a customer get a new VB from GM. Your customer needs to fix this or it will probably happen again. I would also suggest putting in Sonnax’s billet piston, a little added insurance.
If this is a 4t65 it should be a 258mm not be behind 5.3 I think this part # is what you are looking for Sonnax # 84757-01K.Mark Mustard
THEIR IS A GREAT ARTICLE AND PICTURES TO THE PROBLEM YOU ARE HAVING WRITTEN
BY BOB WARNKE IN THE VOLUME 6 SONNAX CATALOG PAGE 58 & 59.THIS SHOULD HELP
YOU THROUGH THIS PROBLEM.
This link is to the overpressure valve that fails the TC. Hope this helped
Thanks to all. We Put in billet piston & TCC Relief Valve Kit. Found channel plate bushing for turbine shaft ring grooved.Mike