Thread: HELP Please!!!! 1997 GTP transmission slipping.... trans has been replaced!

I am hoping someone has encountered this issue and can offer me a resolution.

My girlfriend has a 1997 Pontiac Grand Prix GTP VIN#1G2WP1219VFxxxxxx

She started having an issue with the transmission slipping under heavy acceleration.
What would happen is when you try to accelerate quickly the trans would feel like it was slipping but then would "bang" into gear, then it would slip again and then bang into gear again... this process would continue until the car reached a speed fast enough to shift into second gear or if you lifted your foot off the gas due to the horrible feeling it gave.

I warned her to drive with a easy foot to avoid ruining the transmission, but in time the transmission eventually failed and slipped to the point where the car could no longer be driven.

I brought the car to a certified mechanic friend of mine and he replaced the transmission with a rebuilt one.
As soon as he finished installing the trans he took the car for a test drive and immediately noticed and issue.
The car seemed to be "holding back".
The car would not accelerate with any power at all, almost as if it was taking off in 3rd gear.

Unfortunately for him, he put the car back on the hoist and removed the newly installed transmission.
He then got a second transmission and installed it.

Again a road test revealed the same exact issue.
The car felt as if it was taking off in 3rd gear.

We decided the problem must be electrical.
Further investigation revealed a broken 12 volt supply on the connector that plugs into the transmission.
The wire that was broken was the 12 feed wire that provides power to the shift solenoids.
We repaired this broken wire and it solved the issue with the car feeling like it was taking off in 3^rd gear.
I assumed the transmission issues were resolved and picked up the car.
Driving the car home all seemed well until I was almost home.
The car is now exhibiting the same behavior it originally had when it first started acting up.
The transmission slips under heavy acceleration and “bangs back into gear”.
I found another transmission electrical connector at a local junk yard and replaced the connector that was on the car for fear that there maybe another loose wire on the original connector…..same result.

Has anyone had a transmission issue similar to this?
Does anyone know where I might look next?

Thank you,

Ken

Original transmission I can not say for sure..... car has 180k miles
Replacement transmission was installed Saturday, and yes, another the torque converter came with the rebuild transmission.

Originally Posted by slick2500

I would assume as many miles as it is from the shop to his house plus a few for the test drive of the rebuilt trans they put in.

Slick,

I drove the car roughly 10-15 miles from my friends service shop to my driveway.
I didn't drive the car hard at all on the way home because it was a rainy day here in Michigan.
The next day when the roads were dry I took the car for a ride and that is when I noticed it is doing EXACTLY what it did with the original trans.
Slip and "shudder" when accelerating hard.

It's possible, but I can't imagine a rebuilt trans doing the same EXACT strange problem.

I have been reading alot on this forum and I think my next step is to check the trans for a good ground.
I may even add a heavy gauge wire from a body ground to the trans housing just to make sure it's not a ground issue.

I'm still hoping to read a reply from someone who may have had a very similar or exact same symptom......