2002 GT Vibration, possible diagnosis

[dtunget]

I've recently aquired a 2002 Grand Prix GT. 3.8L v-6, no supercharger. I noticed a fast vibration when the engine is under a load i.e. getting from 50 to 70, up hill under cruise control.

This vibration can be felt when getting from 40 to 50 to pass on city roads too. It's fast, faster than a tire issue, and it's only happening when you're on the throttle. It shakes the entire car and you can't really just feel it in the steering wheel like you would a front end issue.

We're thinking that we have a broken passenger side engine mount, judging from the travel of the bottom of the engine on that side when throttling to 2k rpm in D with the brake depressed. It also clunks real hard when shifting from N to R or D.

Anyone have any experiences to share with these engine mounts? I've got a GM mechanic that is going to do the work for me, he owes me a favor and the part looks to be about $60 if I'm looking at the right one. I just need to know if there is anything else I should suspect and if anyone has had a similar experience.

[GTP Dad]

Welcome to AF!!

It sounds like you are on the right track with the motor mounts. However, while your mechanic friend is working on the car have him check the CV joints on the axle shafts for you. It is possible that one of the CV joints may be going bad since it happens under throttle and between 50 and 70 mph.

[dtunget]

He's gonna do that for sure. We did notice that one of the boots is leaking.

[dtunget]

You wouldn't believe this if you saw it......We've had this car for 6 days and we got rear-ended today while sitting at a stop light. Fun stuff. I'm going to try to get the lady's insurance company to replace the cv joints and engine mounts because of this "new" vibration in the front of the car.

[monkeylizard]

Originally Posted by dtunget

You wouldn't believe this if you saw it......We've had this car for 6 days and we got rear-ended today while sitting at a stop light. Fun stuff. I'm going to try to get the lady's insurance company to replace the cv joints and engine mounts because of this "new" vibration in the front of the car.

As grampa used to say on Hee-Haw...

"Ah don't believe I'd uh told that."

[dtunget]

Well here's a new development in this vibration issue:

about a week ago the Service Engine Soon light came on so we had our guy pull the code and call our buddy at the GM dealership to see what it meant.

The conversation went something like this:

Mechanic: Tell me about code XXXX
Dealership Guy: Does that car shake bad with the engine under a load?
Mechanic: Absolutely, that's the symptom that they're having.
Dealership Guy: That code is for the torque converter
Me: sigh

I never had the motor mounts or anything fixed so at least I didn't go replacing all that stuff before we found this out, however the job just got a little more expensive I suppose.

If anyone knows how much I should expect to pay for a new tourqe converter, any other parts for the replacement, and labor, please advise!

[troy1]

A bad PCS can cause a TC shudder. SO don't condem it yet

[dtunget]

PCS?

I'm going to check the fluid when I get in the same location as the car and see if it looks good and black. Anything else to look for to verify the TC?

Thanks.

[GTP Dad]

The PCS (pressure control solenoid) is located inside the transmission, about a $600 repair. A new torque convertor will cost about $1000 to have replaced. Mostly due to labor costs to remove and reinstall it.

[dtunget]

Saving several hundred dollars is never a bad thing. I guess I need to figure out how to narrow down what the problem is.

[troy1]

You need to take it to a trans shop and have them look at the shift adapt times and the TCC duty cycle percentage and TCC RPM slip. What was the DTC you had anyway?

[dtunget]

DTC?

I'm not really familiar with this car and it's configuration yet

[bangbg]

I have no idea what your status is with this car at this point but I will put in my $ 0.02 anyway.

I have a 2000 Grand Prix GTP coupe with 149,000 miles on it. It developed the same type of vibration/shake/shudder that you described in your initial post. It happened when the drivetrain was under load accelerating or if the suspension loaded up when going on a road that was not perfectly level(gentle up and down undulations). In particular it was worst when accelerating and turning to the right.

In my vehicles case it turned out to need both the left and right side axle shaft/CV joints R & R'd. With that fix it now is as smooth as it was when it was new. All traces of the vibration are gone under all driving situations.

I paid a local shop to do it, for both sides parts and labor was $324.00.

I hope you get the chance to even fix that problem from the sound of your situation.

PS. I had already replaced all 3 of the motor mounts while trying to diagnose this problem, the clunk you describe does sound like a motor mount.

[dtunget]

I'm gonna find a shop here where I've moved to and take it to get proffesionally diagnosed. I think I've learned enough here not to get BS'd into paying for something that isn't broken. The shake + the SES light makes it look like the tourqe converter which would absolutely make the car shake...however it would also shake with bad CV's etc. I haven't heard it happen under steering specifically though, only climbing hills and hard acceleration.

[reidway]

I too have the nasty vibration but only when turning to the right under acceleration and when I am travelling straight over a slight uneveness in the road which makes the suspension load up and the car bounces a bit. turn to the left everything is fine. I noticed the driver side CV boot leasks grease so do you think that may be my problem? someone also suggested a bad wheel hub but it does not make any noise like a bad bearing would. you feel the shake in the drivers seat as well as the steering wheel.
Thanks