Dr. McCoy's scanner on Star Trek

[Mr._Graybeard]

I'm hearing a faint, high-pitched, oscillating squeal while driving my 540i at low speed. Braking doesn't affect it. I've also tried weaving to check the wheel bearings. That doesn't seem to be the source either.

At this point I'm thinking the driveshaft center bearing is going dry. I also get an occasional chattering at freeway speed with the drivetrain loaded, like going up a hill. I think the chattering is becoming more frequent.

I've got the bearing, carrier and guibo on hand for my next free weekend. Just looking for confirmation here, or a warning if my hard work is likely to be unproductive.

[Ross]

Like this?
http://www.youtube.com/watch?v=dtjf6aXfm_Y
does that car have a metal u-joint? My autobox 540 has one at the back of the front half. A dry u-joint will make high pitched noises and oscillates as the bearing speed changes with each revolution.
Look for signs of rust around the seals on the caps, if so it's toast.
http://www.powertrainindustries.com/

[Mr._Graybeard]

That's the sound! It oscillates a little more than that, but Star Trek is what came to mind when I started hearing it a few thousand miles ago. I'm sure it's continuous, but the only time I can hear it is when I'm barely moving.

I wasn't totally convinced about the center bearing, because I've heard a couple bad ones on Audi 4000s -- this sounds much much less apocalyptic than that.

I'll get under the car this weekend and check the U-joint caps. Thanks, Ross!

[Jehu]

Wow. I hear something like this too.. My car is in a shop as I type... is this a potential sudden catastrophicfailure part or can I get to it another time?

[Mr._Graybeard]

I've been living with this for several months, so if that's any indication, you might be OK for awhile. The last time I had a U joint go bad on a car it sounded a lot worse than this (probably because I ignored the squeaking, dumb kid that I was), and it was driveable enough to get it home and take it to a shop. I suspect the condition would have to be grossly neglected before it would leave you at the side of the road.

If your car's in the shop now, though, it seems like a good time to have it looked at to confirm the diagnosis. At that point the tech could check for play to see how far gone the joint is.

Here's a pretty good tech article that will give you an idea what's going on if the driveshaft U-joint is your problem. It's for Jeeps, but I think the principle is the same for the U-joint. http://www.jpmagazine.com/techarticl...101/index.html

[Jehu]

Yah I've noticed it a few months now but i keep forgetting. I thought it was just soemthign rubbing. I only notice it when rolling slowly along with a window down and in close proximity to a wall or soemthing off which the noise gets reflected ... thanks for the info.

[Jehu]

Update... The noise on my car turned out to be some heat shield which was rubbing on a rotor...phew..