i got this 92 grand prix for my daughter that looks like new . it has 93000 miles and was a one owner car and she past away . i was told it had tranny probs but it was still worth what i gave for it .

this is what it does . put it in drive and you can feel it go in to gear . then you touch the gas and it slips ( so bad it just wont move ) and reverse is the same . there is a rocker switch that has start in 2nd gear . when i push it the car will move just fine . than i noticed that on the road it will stay in 2nd . switch it back to normal while your moving and it still stays in 2nd gear . after messin around with it for a while and it started working fine . i shut it off and started it back up put it in reverse and it backed up fine went to drive and it started to take off and it was like i shifted to neutral and went to slippin again . this car was takin care of and i just cant beleave this tranny is out . it only has 2nd gear and its the only gear that works right . please help

You have an early model 4T60E transmission and the computer controls the shifts, and a vacuum modulator on the front of the trans controls line pressure. If the modulator is bad it will cause very low pressure and slippage an all gears. There is a vacuum line on the front of it, the modulator is a round gray can on the front top of the engine and will have a vacuum line coming out of it. Check the vacuum line conditions and make sure there isnt trans fluid inside it. Without a vacuum pump you wont be able to check its operation. If that is fine then you have an internal problem. Were you given any info on the trans problem when you bought the car? Any history to the trans? Have you checked the fluid level when the car is warmed up and engine running with shifter in park?

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4T65E Transmission Info
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the only thing i was told was the trans was weak . and it is full of fluid and i seen the modulator and the hose your talking about . i do have a vacuum pump so i'll check the line . if the modulator is bad will it have fluid in it or can it be bad w/o fluid in it also ?

It can be bad without fluid leaking. The best way to check the modulator is to remove it from the trans and hook up your vacuum hand pump and watch the rod in the trans side move in and out, in with more vacuum. Make sure vacuum will hold and not bleed off and that it appears to function ok. No vacuum means harsh shifts, high vacuum or stock valve can cause soft shifts caused by the low pressure. There is a valve behind the modulator that sits in the trans, if you have a small magnet you can see if the valve is free or not. If that checks out ok then you have an internal problem.

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4T65E Transmission Info
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how much is this rod suppose to move ? i'm getting it to move in and out but only like a 1/16 on an inch . and it does hold vacuum .

correction , i had a old one in the shop that looks alot like the one i took off the car . well thats the one i checked like a goof . went back out to the shop and realized what i had done . the one i took off the car and yes its the one i took off lol is full of trans fluid and will not hold a vacuum at all . called napa and they will have one in the morning . man i hope this fix's the problem . i just hope they didn't drive it like this to long .

well i have bad news . had to get the new modulator at the dealership and it was $126.00 and didn't fix it . so i guess its off to a trans shop to get a rebuild . thanks for all the help and i'll keep you all updated when i get it back .

Ouch! I didnt know you could still get OE replacements, sorry that didnt fix your problem and I hope you find a good shop to take care of your trans.

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4T65E Transmission Info
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