Ed Taylor

Hey Guys,
I'm trying to locate an unusual sound that seems to be coming from the right rear. Car is an 87 s4 auto that I have owned for a little over three years. All four wheel bearings have been replaced. The noise is ground speed dependent and does not change with road surface construction. Sounds a little like bearing noise. Boots were replaced on axles right after I bought the car. Can not find any unusual play in the joints but the axles do seem to be original to the car. 125,000+ miles on the clock.
Can a failing axle create such a sound without any of the clicking sounds associated with FWD cv joint failure?
By the way I have also tried adjusting tire pressures from a low of 32 up to 40 to try to eliminate the noise being tire related. I am running GTS spec wheels and tires.
Thanks for your help and guidance.

worf928

Since you have replaced the bearings and you cannot find play in the joints I'd first suspect wheels/tires.

Is the noise accompanied by a vibration? Is the noise rhythmic at all?

What kind of tires? Tread life left? Even wear?

I've found that some models of tires become incredibly noisy after a few seasons and/or as the tread depth goes down irrespective of pressure. P6000s and SO-2s in particular.

If you have a speed-dependent vibration it could be tire balance related.

I, very recently, 'fixed' a horrific above-75mph-vibration with accompanying noise by having all four wheels/tires rebalanced.

Garth S

This is one of the more difficult sounds to sort out, even when in the driver's seat. As far as bearing and CV joints, I suspect you've already jacked up the rear and spun/twisted/ pulled wheels and shafts.
As to the noise, did it start suddenly - or did you just become aware of it? Has it changed with time?
Changing the tire pressures is a good thing; however, as tires wear, either normally or irregularly (due to misalignment) they can generate some unusual noises. I have SO-2s on the S4 that make a wheel bearing type of noise: Thinking that it was a bearing, I swapped the tires/wheels from another car (Michelin Pilots) - and the noise changed. Everything seems tight, so I motor on - every now and again thinking, " is that really a wheel bearing?"
Just for fun, try swapping the rears side to side (even if they are directional) for a short drive.

Old & New

Did the noise exist before changing the bearings? Perhaps a defective bearing, or damaged upon install.

Ed Taylor

Tires have been recently balanced on a hunter machine. No unusual vibration.
Bearings were changed over two years ago, sound not associated with bearing change. I let a local shop press in the new bearings for me while I watched.
The sound is the same no matter what type of road surface I am on:smooth asphalt, rough asphalt, concrete.
Wear is even on rears. Not down to wear bars quite yet. Kuhmo Ecsta.
I have not swapped the tires L/R to see if the sound follows, maybe I should. My thinking was that if the sound did not change with tire pressure or road surface changes then it probably was not the tires?

Gretch

lug nuts tight?

One way I have isolated sounds to a specific corner of the car is find a brick or cement wall you can drive by slowly. Parking lot with a retaining wall or a brick building with the parking lot right up against it. Roll your window down and drive by the wall and see if you can detect the noise. If the noise occurs it will bounce off the wall and you will be able to isolate it pretty well. The sound is also amplified in its natural state, so you maybe able to hear things you couldn't under normal driving conditions. It has worked for me in some cases ..................

Jim bailey - 928 International

The mud and snow rated tires which we all seem to like for their "aggressive" tread patterns very often are quite noisy as they wear . I do find it somewhat amusing that most performance tires all have big clunky tread patterns with lots of open areas ..no rubber ; when it is the rubber which grips the road . OK I do remember that it does rain in certain parts of the world .

TeufelHei

FWIW, I've got the same issue with my 81. No idea just yet but it's been suggested that driveline hardware might be loose or transmission mounts might be going. I can't offer much more than that since I haven't really driven the car in a few months (just around the neighborhood to keep her going).

Ed Taylor

Gretch, Yep my nuts are tight.
Jim, Never saw the "Z" rating on the 32" I used to run on my K Blazer.
TeufelHei, Definately road speed related. Gone uphill down hill under accel. and aggresive decel, revved the engine in neutral.
I am going to swap the tires and see if it changes tonight. The Kuhmos have not worn as well as I had wished and this sound has kinda snuck up on me slowly. Maybe it's the tires after all.

OT- Was cleaning and waxing my 84 yr old Dads Caddy Catera this weekend when much to my suprise there on the label on the door jam:
"MADE IN GERMANY"
Go figure?

Jim bailey - 928 International

The Catera was an Opel design rebadged , skinned as a Cadillac and assembled by Opel (German GM) .

Ed Taylor

Thanks Jim. I haven't kept up with any of the Opels since they quit selling them in the states. I was not in favor of him buying it but he likes it so far( fingers crossed)
pps. It just started raining. Glad I got them aggressive treads

Tony

Ah..the always forgotten parking brake assembly!

Thats my bet.

Pull the lever up slightly as you drive and see if that changes anything?

Old & New

Ed,

Is it a dry or growely bearing-like sound?

Maybe put it on dyno / rollers for testing.

FWIW, I liked my '70 Opel Kadett 1.9; it was very utilitarian, well built / reliable and pretty zippy.

Adam Opel company.


Tony,

Sure beats most of the alternatives.

Ed Taylor

Tony: No problem with the parking brake or the flaps.
Old and New: Looked at an Opel Gt once. Fun car.
Swapped the rear tires and the sound changed. By the way OMG the directional tread pattern doesn't work worth a flip running backaswards.
removed right rear wheel, supported lower arm so that axle would be level. Car does not have LSD. Ran it up to 65 MPH not a sound to be heard. Just for kicks and giggles did the same test on the driver side, no noise.
"Must be the shoes."
Strange that it doesn't change with road surface.
Thanks for all the feedback.
Now to decide what size and brand of tires to buy for my 17" 7.5" front 9" rear.
???

worf928

Yup. I mentioned the SO-2 and P6000s. What do they have in common? That really cool looking water-pumping ">>>>>" tread pattern. And OH BOY were they noisy once they started to wear. The p6000s in particular only stay quite for the first winter while the SO-2s (not M&S rated) just seemed to get steadily noisier - to the point where they were louder than the failing rear wheel bearing...