Very Confussed - Trans slipping in ALL Gears, converter works fine.

[Badvw68]

Ok guys, any and all help would be great. I have a 99 Grand Prix GTP with 110,000 miles. I am aware that these cars are nortorious for trans problems, but in doing research, I cant find any of the same problem as mine.

Yesterday, on the way to work,the car ran fine, as it always has. I left work to come home yesterday evening, and when it shifted into 2nd, it made a noticable jerk (2 times) then shifed. Well this got my attention!! From there on, the car still shifts, but has a really delayed shift. If I give it a fair amout of gas, in any gear, it slips. If I baby it, it doesnt seem to slip. Once the torque converter locks up and it runs flawlessly assuming it doesnt disengage.

I serviced the trans about 25,000 miles ago
I check the fluid level yesterday, and it is still full
The fluid was still red, but did have a little burnt smell

Guys, the only thing I can picture happening here is a few things:
For some reason, the line pressue is low, causing it to slip in all gears.
- The filter clogged?
- Pressure Solinoid? - I do not know the location to replace

It would make more sense to me if it was only one gear slipping - Clutch pack, but all gears have really got me stumped.

Please let me know what you think. I really would like to avoid the trans rebuild if that is NOT what I need. The car is not really worth a 1500.00 investment. I am hoping it is a solinoid or something I can pull apart at home or check at home.

Thanks for any help! Alden
Sorry for the long thread!!!

[BNaylor]

Welcome to AF.

A common problem is the PCS solenoid. I would get it scanned with a trans capable scanner and see what DTC codes are stored. Look for codes such as P1811 which may indicate you have PCS problem. It controls line pressure. Also, any TCC or slippage codes. Certain codes do not trigger the SES light but are stored for retrieval.

This type tranny work is not typically DIY.

Replacing the PCS solenoid requires major disassembly since it is located under the side cover with the valve body.

[Badvw68]

Thanks Bob!!

I just cant imagine that it is anything else but low line pressure.

The PCS Solinoid - I am unaware of where exactly it is, but depending how far you have to tear the trans down, I think I should be able to do it. Do you have to remove the trans or is it above the valve body?

Thanks!

[BNaylor]

You're welcome. Line pressure can be tested to see if in specs. There is a fitting at the top of the tranny. To get to the PCS solenoid or any component at the valve body the complete engine/tranny is dropped down on the subframe cradle intact. It is a PITA of a job but can be done DIY. I have a general procedure for FWD GM vehicles if you want it. Let me know.