Nasty rear end buzz

[yeeha68]

I have come to a point where any suggestions are appreciated. I have a nasty buzz in the rear of the car. It starts at 40 MPH and grows with speed. It is not engine related as I can push in the clutch, or slip into neutral while moving and it does not change. It sounds and acts like noisy tires, but they are in good shape and only 4 months old. It just appeared one day out of the blue, and wont go away. There is no noticeable vibration in the car, or on the clutch. It is not effected by taking turns or braking.

I have repacked the CV joints, changed the gear oil, and checked the bearings with no change. I suppose the bearings may be bad and I just cant tell from close inspection, or manual spin.

With the car lifted and the wheels running in gear the noise cannot be found or heard. I cant think of anything else it might be other then the transmission, but changing gears does not effect the sound. Only velocity effects it.

I'll take any suggestions even if they require ritual dances around the car. :notworthy:

'98 boxster

5 speed

75,000 miles

[RFM]

I give it a try with 4 wheels coming from the same type of car with approved N coded tyres if i was you, simple, cheap and efficient solution.

[rsfeller]

I always consider bad bearings a "groan" and not a buzz. I have had brand tires (twice) develop a cup and cause a noisy buzz. Have you confirmed no cupping on the tires?

[Topless]

Oversize tires rubbing on break components?

[yeeha68]

Tires are stock size, and dont look like they have a cup. Ill try swapping them out next.

[yeeha68]

Well, I tried swapping tires around (I dont have additional tires available) and the plot thickens. It would seem that when the spare is on the rear passenger side the noise goes away. This is odd because the buzz is not present when either of the existing tires is used on the drivers side. However, when you put the front tire on the passenger rear side (wider then the spare, narrower then the rear) the buzz is present at about half the volume. The Conclusion: the wider the tire on the passenger side the louder the buzz.

Im at a loss...I can only come to two resolutions: 1. the tires have worn to create a resonance buzz, or 2. The toe is placing a torque on the bearings and they do need to be replaced.

Any suggestions before I breakdown and drive to the dealer?

Edited January 7, 2008 by yeeha68

[juniinc]

IM WONDERING .whats the depth on your tires? have u measured it yet?

if bearing was going out ,would make a humming noise rather than the buzz

Well, I tried swapping tires around (I dont have additional tires available) and the plot thickens. It would seem that when the spare is on the rear passenger side the noise goes away. This is odd because the buzz is not present when either of the existing tires is used on the drivers side. However, when you put the front tire on the passenger rear side (wider then the spare, narrower then the rear) the buzz is present at about half the volume. The Conclusion: the wider the tire on the passenger side the louder the buzz.

Im at a loss...I can only come to two resolutions: 1. the tires have worn to create a resonance buzz, or 2. The toe is placing a torque on the bearings and they do need to be replaced.

Any suggestions before I breakdown and drive to the dealer?

[yeeha68]

They are standard size tires. 255/40/17. about 10" deep. They are Michelin Pilot Sport tires.

[juniinc]

I meant for the tread depth? brand new are like 10/32" but when they get lower than 4~5/32" some tires can be very noisy.

if it make a squealing sound, grinding humming noise usually... change sound as u turn...buzzing then definitely the wheel bearing.

Grab the tire at the top and bottom and move the tire back and forth, if there is any play (looseness) the wheel bearing could be bad.