Thread: 99 grand prix GT tranny ??

Hello,
Have a 99 grand prix. Drove to work this AM and ran like a gem. Parked and went out tonight and it runs about 35 ft and the tranny goes into neutral or so it seems, nothing in any gear just gone. Then if you shut off car and wait a minute and restart it does it all over again. Runs strong and perfect for 35 ft and then start over etc. It feels either electric or linkage based. But who knows. Thanks for any and all input.

It was dark and full. Seemed a tad runny to me. Didn’t smell burnt at all. Kinda wondered if something might have froze also.

I’ve read up on something with a clip under the shifter that might cause this ? Have you heard of that ? I’ll try pulling a code tomorrow

From Dave at triple edge performance:

No Forward Cold



No Forward Cold, Neutrals at stops, Shudders on take off:

One of the most common problems I have found after the milege gets over roughly 60K miles. The scenario.... You are driving in traffic for a while OR your car has sat for a while and is a cold startup. You put the car in Drive range and it wont move, or if driving you come up to a stop light and in heavy traffic and the light turns green and SUPRISE!!! You are holding up traffic with a car that wont go anywhere. The most common cause of this problem is a worn out inner surface of the Input clutch piston. I will post pics soon so you can better understand why it IS a real problem. Once the inner sealing area wears it can prevent the inner lip seal for the piston from sealing properly. You may find that revving th engine up will finally get the car to move and it will BANG into gear. This is because the pump in the transmission is working harder and moving more fluid thus allowing the added fluid to overcome the leak which prevented the clutch from either initially applying or staying applied. From the factory the rubber lip seals that are used on the inner and outer sections of the input cluch apply piston are a Short design seal. The transmission repair service field has found that a Long style lip seal greatly helps against this problem and is what is included in aftermarket gasket and seal kits and is also what we use in our rebuilds. New seals from GM are still the short design and offer no benifit over the originals. Another area of concern that causes this is a boost valve in the valve body, not near as common but it can cause this problem on a lessor scale. If a fluid/filter service has not been performed in a very long time then a very dirty or plugged up filter can add to problems as it because a major restriction. IF the filter is found to be very dirty on the inside, which can be verified by cutting open the filter, then there are other problems inside the transmission anyways and an overhaul is the only correct way to fix the problem. Sometimes servicing a transmission with this condition will make the problem worse, so dont feel that you need to rush out to have a transmission fluid service done to make the transmission work like new again because it isnt going to.

Does this car have a TCM or is it all run by the PCM ? Thanks

I’m going to hook up scanner now. It took another turn this morning. It’s about -15 here and I went to start it this morning and it ran fine. When I put in gear I had nothing, it was like the shifter was unhooked. Then before I could even get out to open hood it began running awful and killed. I attempted to unhook the MAF and restart but it won’t start now. I just replaced the MAF,MAP and TPS sensors. I’m thinking it’s the PCM but who knows