audijim113

Never a dull moment with A8 with 180K. (2000 A8L). Returned from a 1500 mile trip, no problems but now i notice a vibration/noise. It seems to be coming from the rear. At first it was around 45 mph and could be felt on accel/decel and quieted over 50 MPH or lower speed. Now it's pretty much all the time, starts around 45mph but is evident especially at highway speed.

It doesn't feel like a tire or bent rim vibration of shake. More like a shudder/vibration loud hum like the vibration of a commercial passenger jet from the engine on those with the engines on both side of the rear. I feel it in my butt. Back passengers feel it more.

Is it a wheel bearing or a drive line issue? My rear different seals have only been very slightly wet so i don't think it's that but don't know.

I seem to remember someone telling me the rear wheel bearings are more prone to fail than the fronts. Any thought on this? What's involved to replace and most importantly, is there chance of catastrophic fail if i continue to drive it?

silverd2

Need to start with a good, thorough visual check >>

- Recent oil loss at rear diff (then check the level)...a dry diff can be noisy and always speed sensitive.

- Look at rear diff mounts (collapsed, torn), including rubber bushings on cross member.

- Boot on rear end of drive shaft CV boot...get hold of drive shaft to feel for side play (at diff or middle of shaft)...radial play is normal.

- Look at all 4 rear CV boots...rips or leaking gray grease.

Wheel bearings are always side load sensitive...should get worse or better in left or right turns.

audijim113

At one time, I would have crawled under and checked this myself. instead, I took it to my front end guy (probably one of the best in the business). He was busy but called me late yesterday and asked, "who was the last person to have wheels off? To my knowledge, it was when he put 4 new billstiens on in August. More recently, he replaced the bent,shaking right rear wheel with the spare which smoothed things out. The problem with this vibration was traced to the left rear lug bolts were slightly loose. The vibration started shortly after returning from trip to NYC and got progressively worse.

Tightening / torquing the lug bolts eliminated the vibration except for the wheel which also has a slight bump but I've known about that and vibration from that is about a 1 out of 10 compared to what i was feeling with the loose lugs being 7 out of 10. Vibration was felt through my butt so the scale I'm referencing is built into my ***.

The only other service it had was an oil change before leaving on 1500 mile trip, Oct 17, which included a casual look over. The list with checks included "brakes, ok". Talking to that place this morning, they only looked through the wheel and didn't take it off.

It seems odd that I could have been driving since August with a number of smaller trips 100-200 miles), plus daily driving and not noticed the loose lugs. Given the wheels are aluminum, is it possible the trip and heat generated / expansion contraction might have loosened the lugs? Is there credibility to a comment that lugs on aluminum wheels should be retorqued after 100 miles? Is it possible that wheel with a minor shake due to bumped rim might have shaken it loose?

I'm now going to look for one good wheel (factory original, optional 18") Any suggestions for a source? There have been several 2000s listed for parting out but they are on the left coast and i hate to pay shipping for a wheel, plus i'd really like to see the wheel before buying.

S8ilver

http://www.ebay.com/itm/AUDI-A8-S8-Q...2f61e2&vxp=mtr

S8ilver

Oops, was readying "01-S8"'s post and had "01 S8 wheel" in my head.

Was there only 1 style of 18" wheel for A8L?

http://www.midwestwheelandtire.com/product/1088

No way I'd pay that for one wheel though...however I don't know the alternative besides someone parting out. Craigslist?

S8ilver

http://www.hubcaphaven.com/mm5/merch...egory_Code=663

S8ilver

http://www.partsultimate.com/product/158242