Michael S.

I have a strange noise coming from the front of my 05 Cayenne S... Done a bunch of searches, and nothing matches exactly. I had hoped that it was worn brakes, but just finished replacing pads and rotors tonight and the sound is still there...

It seems to need to warm up first. Then it is speed dependent... sounds almost like a dragging brake pad and gets quieter (but doesn't go away) under braking. No change when shifted to neutral. Seems to be quieter when turning hard left than when rolling straight or turning right. I'm thinking wheel bearing? But, it doesn't sound like a bearing noise... Hoping it's not a diff...

Any help is appreciated! We are going on vacation tomorrow, so I guess we'll be driving the Audi...

wirunner

When my rear brakes were replaced, the dealer accidentally had bent the thin protective plate behind the brakes and it was rubbing on the rotor causing a sound exactly similar to what you describe. Not sure if front brake setup is the same.

If you are familiar with wheel bearings, their sound is pretty distinct when going bad. Hard to tell just by reading it here unfortunately.

XR4Tim

Lift the front of the car and shake each front wheel to help rule out wheel bearings. I replaced a front wheel bearing on a 955 that made a loud grinding sound at low speeds. Grabbing the wheel by the spokes and shaking up and down made it obvious just how loose the bearing was.

Michael S.

Had it in the air yesterday when replacing the brakes... Nothing loose that is noticable. And, I would not describe the noise as a "grinding"... More a high frequency scraping or whining...

Michael S.

I've decided it must be some sort of "gear whine"... Likely the front diff. I will do a fluid change (125k miles), but not optimistic... Where is it you can send oil for analysis? How much $$ for the analysis? How much $$ for a replacement Diff? How difficult is the install? DIY?

uh60pin

What speeds does your noise occur? I have a similar noise on my 05 CTT, it only has 44k miles on it also. I can't tell if it is a wind noise or something mechanical, but definitely seems to be coming from the front of the vehicle. My noise is most prevalent in the 50-70mph range.

Michael S.

Probably 40 - 70mph... Though I doesn't go away, I just haven't been higher to verify. It reminds me of an old truck's transmission... The more I listen to it, the more I know it's gear whine... I just have to determine the source.

SCOTITUDE

BTDT, front diff blows, gotta drop the whole front cradle. Look at bearings, CV/s and axles before diff. the front bearings are pretty beefy. you might not feel a wiggle by just checking the wheel. Bearings groan, axles go crunch, low speed tight turns. At your mileage id start there, after you check the backing plates and make sure they are not hitting the rotor.

Michael S.

Ok... So, tonight I replaced the fluids in the front and rear diffs and the transfer case. Big surprise, no change in the noise. Oh well, with 125k on the odo, they were all overdue replacement anyway. On my testdrive tonight the car started making the noise almost immediately... Throw the pig into a left bend, and the noise is gone... throw it into a right hander, and it gets a bit louder. Then I get on the brakes hard (almost into the anti-lock) and the noise is gone... drive it for another 10 miles or so, and it never came back! Dammit... I hate these kind of problems!

So, it's now looking brake related... though it can't be pads, as I just changed both pads and rotors... Maybe a sticky piston in a caliper, but noting felt funny when replacing the pads, and no odd wear on the pads I removed... If something is sticking, it's just enough to cause some noise, and not enough to generate any siginficant heat or pad wear. Any ideas as to how to best isolate which wheel a noise is coming from? I can't hear the noise when the windows are down, so maybe I can get the wife to drive around whilst I climb around in the car with my automotive stethoscope. I'm open to any and all ideas...

Orantes

Opps, sorry, null post...Good luck anyway!

Michael S.

Question for all...

Would I damage anything if I lifted my Cayenne off the ground by a few inches, then put it in gear to try and help isolate where my noise is coming from? I know mechanically it should be ok, but there are so many electronic nannies (traction control primarily), that I am afraid to test this way without someone telling me I won't burn something up...

Michael S.

Anyone?

XR4Tim

They don't particularly like to drive without the wheels on the ground. Even with PSM off, you'll still have odd things going on (one or two wheels braking on their own, warning lights, etc.).
Also, since you have air suspension, even if you turn it off, it will automatically re-engage when you hit a certain wheel speed, which could cause other problems.

Michael S.

Thanks Tim... I have in on the lift right now and everything looks good... I can't help but believe that I am just dealing with a sticking caliper piston... The noise is still very intermittent and frequently goes away with a stab of the brakes.. Not always, but often... I hate these sort of problems!

Michael S.

Yet another update... I have now replaced the right front caliper to the tune of about $300, and I am still fighting the noise. I purchased a "chassis ear" off of Amazon for $50 (a bargain!) and still cannot positively locate the noise. The transfer case/center diff has a lot of gear noise, but it is consistent and doesn't sound anything like what I am hearing. The noise still gets quieter with the application of brakes, but never really goes completely away. I also hear noise from the front diff, but I refuse to replace a $2k part without a positive diagnosis...

Anyway, I have the pig scheduled at Hendrick in Charlotte on the 25th... We'll see if their wrenches are able to make any sort of diagnosis. I know I am only a shade-tree mechanic, but I am usually pretty good with this sort of thing. I hate the idea of paying a dealer $100 a hour for some 20 year old to tell me nothing constructive... Guess we will see.