Mechanics

VIBRATION

1999 Pontiac Bonneville

Shakes or Wobbles problem
1999 Pontiac Bonneville 6 cyl Front Wheel Drive Automatic 86000 miles

1999 Pontiac Bonneville with 86,000 miles has vibration in seat, and little in steering wheel. Slight vibration at 50 mph, very noticeable at 70 mph. Vibration becomes worst and then gets better, then worst, at any given speed. Tires have been balanced twice. I switched tires with known good set - vibration basically stayed with car. There is a small cut in rubber boot of right 1/2 shaft. At 30 MPH, you can hear a noise in front that I thought was tires at each rotation. Now I think it may be front wheel bearing or half shaft.

Have you ever heard of a bearing causing a vibration?

Is there a likely cause of the vibration?

Any diagnostic I can do rather than just change parts?

Thanks,
Ed
Avatar
Edroelle
August 24, 2009.




If you feel it more in the seat, chances are the problem is in the rear. Yes a wheel bearing can cause it, but did it change at all with the new tires?

When I changed tires, the vibration continued in the car.

I recently drove the car on a long trip and at a constant 65 MPH, the vibration would get worst, then better, then worst - but always there to a degree. All tires were balanced twice. I had considered that the phase relation between tires could have changed the vibration, but I have ruled that as unlikely because of the balance.

Tiny
Edroelle
Sep 8, 2009.
Did you check for a bent rim? Also, is there any play in the rear bearings? Are the shocks good?

That is a good idea to check for a bent rim. I should have done that. I will. My daughter has the car and I will put a dial indicator on all the wheels. They are aluminum so I would not expect any to be bent. An aluminum wheel would not bend very far before cracking and failing, would it?

I saw no wheel bearing play.

Shocks are good.

Thanks,
Ed
AD

Tiny
Edroelle
Sep 8, 2009.
They do bend, but you are correct. They won't bend too far without cracking. It could be the problem.


AD