Pontiac Repair: no overdrive, sludge deposits, pontiac dealer

Question
QUESTION: 01 grand prix 3.8 nonturbo 64k miles no overdrive at all, tranny works fine otherwise. low temp thermostat in engine runs at 160 degrees never goes higher, heater reflects this temp also. Have seen lots on the net about this same problem. Any suggestions?

ANSWER: Hi Paul..

I'm not a transmission tech but I'll try to help you out.. what happens when the car is hot and you drive it up around 40-45 MPH? does it neutral out or does it just not upshift into 4'th gear? if it neutrals out meaning the engine rpm's go up and the car is no longer being driven by the transmission ther is a problem with 4'th gear mechanically... if it just doesn't up shift and stays in 3'rd it can be a control issue with the computer or an issue in the valve body of the transmission.. what other modifications have you doe to this other than the cold thermostat? That is NOT a good thing to do it hurts fuel economy and in the long run it will speed up sludge deposits in the engine and cause increased wear on engine parts. The hotter it runs the better it is...


---------- FOLLOW-UP ----------

QUESTION: all engine work was done by a Pontiac dealer the low temp seemed unusual to me. the transmission does not shift above 3rd, you can pull the shifter into 3rd at any speed and it doesn't change r.p.m. or anything. engine runs at approx 3000 r.p.m. at 55 m.p.h.and loves gasoline.

Answer
i STILL STAND BY WHAT i SAID BEFORE THE FACT THAT IT WILL NOT UPSHIFT IT HAS TO HAVE COME KIND OF A CONTROL ISSUE GOING INTO OT INSIDE THE TRANSMISSION. WITH OUT THE USE OF A SCAN TOOL TO SEE ACTUALLY WHAT'S GOING ON WITH THE TRANSMISSION IT'S REALLY HARD TO SAY FOR SURE. nO SERVICE ENGINE SOON LIGHT ON?