Shimmy, not tire related

[xxdabroxx]

All the motor mounts good?

[J Wikoff]

They were new less than 20k ago. I can check them out though.

[xxdabroxx]

Loose nut behind the wheel?











I kid....

[96 SSEi]

Actually, I think I'll do the ball joint while I'm at it.

hi, my 92 GTP was doing the same around 300k and it was the ball joints- they were badly worn

[RJolly87]

Take this information as you wish.

I have a similar shutter in the PA too, and it feels like it's in the right front. I am betting however, its in the left rear now that I think about it. When I did rear brakes, it was obvious that things were cooked so bad back there that everything is wrecked. It led to this post:

http://www.pontiacbonnevilleclub.com/fo ... 39054.html

I won't know until I try, but I think the left rear hub plate is warped, and I will likely have to replace the hub to correct it, because that is the only thing left back there.

Essentially, it feels like a tire out of round or balance, but its the brake dragging on a portion of the wheel rotation. Simple check for you would be to jack the rear and see if the rears rotate smooth, or if the brakes grab on a part of the rotation.

"When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth."

[J Wikoff]

I'm trying to decide... if I replace the driver front strut and it doesn't fix this issue, do I throw one part at a time at the rear and do some things repeatedly as I go further in (like replacing the ball joint, then undoing it later when I do the control arm bushings) and having the issue probably linger longer, or do I go whole-hog and do struts, wheel bearings, drums, ball joints, control arm bushings, and tie rods all at once?

[xxdabroxx]

Have you jacked up each wheel independently and checked for play. Rock the wheel up and down, left and right? That's how I found my front hub going out on my truck that the alignment shop couldn't figure out. Real scientific like...

If you jerk the wheel quickly and let it recenter on its own does it induce the shake? Another symptom of my truck when the hub was bad.

[J Wikoff]

When I redid the rear lines and cylinders a couple years ago I did that test and don't remember finding any issues. The shimmy predates that.

[J Wikoff]

I just got the rear in the air. There is no play 12/6 or 10/3 at all. Both wheels spin very smoothly and evenly. I can see one drum is a bit out of round, and does not make any once-a-rev noises. The opposite drum isn't visibly out of round, but it does make a once-a-rev friction sound.

What do you think, maybe replace the drums and bearings and leave the rest alone? I got the other front strut done today. I'll test drive after the rain clears out.

[RJolly87]

If there are concerns with the drums, I would at least address that. I would feel like parts are just being thrown at it if you did bearings without a good reason.

[RJolly87]

But it sounds like the condition you are describing is generally regarded as normal.

[J Wikoff]

I've been throwing parts at it this whole time. I have no issues with that really. Lol

I did rock the car and listen. There is a small clunk as it starts to roll forward again. It sounds like it's on the driver side down near the steering rack, but i can't see anything move. I crawled under and looked. It doesn't look like the rear driver side trans mount or any of the subframe bushings have ever been replaced like I thought. After driving it, the driver side strut didn't fix it either. It still feels like a front end issue with the way it comes through the steering wheel. I think I should address those mounts before anything in the rear.

[J Wikoff]

Assuming no welding in patch panels is needed, does this Dorman kit work in all 6 places?

http://www.rockauto.com/catalog/moreinf ... 680&jpid=0

[MKMike]

Technically, they are replacements for the 4 rear bushings.
They do fit in the slots for the front bushings, though.

The first symptom I had noticed was a clunk/thump when braking.

[J Wikoff]

OK, I tried to replace the subframe bushings today. The good news is none of the nuts broke free. But I do need a new subframe. The rear holes were rusted out. One rear bushing is doing almost nothing. Couldn't pry any of the other 4 bushings out at all. I did replace the rear two and the shimmy did change. At times, cruising, it seemed lessened. Off throttle at highway speeds, it got worse.

[desertpierat]

have you tried switching your front and rear wheels to see if that makes any difference? If you move the front to the back and the shimmy seems to move from the wheel to the seat, you have a bent wheel or tire out of round. if nothing changes, you can rule out the wheels. if it goes away entirely, then have a beer. or two.

[J Wikoff]

Wheels and tires have been ruled out.

[MattStrike]

I wonder if it's pronounced enough that a passenger in a chaser car can narrow it down? Another thought is to swap the front rotors left to right, while they're off check the vents for something stuck in them causing imbalance.

[J Wikoff]

Since the behavior changed when I monkeyed with the subframe bushings, does that not mean that's what it is?

[95naSTA]

How many miles are on the rack it's self and how does the driver's (only) rack bushing look?

I'm with you on the subframe bushings probably being the cause but I didn't see the above mentioned on a quick scan.