1999 Grand Prix Transmission headaches...please help!

[istorm70]

I have a 99 Grand Prix GT with 3.8. The last month or 2 I'm experiencing several transmission problems:

Starting out from the lights, the car shudders and slips (in all gears except first - if I put it in first I can punch it and no slippage)

Going up hills at about 50-60km/h the car starts bucking - like it's shifting in and out of 3rd and 4th

At highway speed, the rpm's are constantly fluctuating up and down (like it's in 4th, and then "almost" goes down to third....even on a flat stretch the rpm's are always going up and down

If I have 3rd gear selected, the car seems to shift into third, and then almost immediately shifts into 4th

I am trying to decide which way to go with this (dealer or transmission shop), any advice you could give I would really appreciate.

[cerick08GP]

Well, since you asked, I would take it to a tranny shop. I say that only because it will save you some coin. But I would ask around for one that has experience with the 4T65E, and definitely put in a hardened 4th gear clutch hub. Good luck.

[istorm70]

Do you have any ideas on what the problems could be? Just don't want to go in blind without any ideas on possible causes.

[GTPJOE90]

inspect the teeth on the sungear and the 4th clutch hub "talking from personal experiance" Triple Edge Performance - Home Page PROBLEM SOLVED

[Zef_66]

inspect the teeth on the sungear and the 4th clutch hub "talking from personal experiance" Triple Edge Performance - Home Page PROBLEM SOLVED

While this is often a problem on higher mileage cars, none of the issues that he mentioned points to this problem.

First things first, check the transmission fluid level when the car is warmed up, running, in park on a level surface. If it is low, top it off and look for where it is leaking.

If you haven't changed the fluid and filter in awhile, that would be a good place to start. But I doubt it will help you much.

Overall, your best bet is going to be a trans rebuild. You have a couple issues going on there that is going to need an entire rebuild. For this, I would go to a respectable local transmission shop. The dealer is known to rape you on price.

[istorm70]

Thanks for the info...I know that the fluid is OK, I just did a fluid change and the level is good. Today it was really bad on the highway, just up and down rpm's constantly...lurching going up even small hills.

I will avoid the dealer and try and find a local shop that has at least some experience with the 4t65e.

[Zef_66]

Thanks for the info...I know that the fluid is OK, I just did a fluid change and the level is good. Today it was really bad on the highway, just up and down rpm's constantly...lurching going up even small hills.

Check it again. Make sure the car is hot, in park, and level. And then check it. And check it again. I typically check my tranny fluid every day for 2 weeks after I change my filter and fluid. The level will change.

But I am still of the assumption that you will need a rebuild.

[istorm70]

Will check again....good point I havent checked since just after the change...have it booked into Tranny shop tomorrow though to diagnose. I'll keep you posted about what they say problems are.

[Zef_66]

Will check again....good point I havent checked since just after the change...have it booked into Tranny shop tomorrow though to diagnose. I'll keep you posted about what they say problems are.

Maybe a little late, but make sure you check the fluid before you take it in.