4kq grinding drivetrain/differential/axle

["ScandurroDM" <scandurrodm@gw.arlaw.com>]

I've just rejoined this list after a few months' absence.  I've checked the archives for my problem, to no avail.

I'm the original owner of a 1986 4000 CS Quattro with about 140,000 miles.

Starting a few months ago, I've had a grinding/scraping sound coming from under the front of my car.  It could be the drivetrain, front differential, front axle, or some other part.  It's not a wheel bearing, because it's from the center of the vehicle.

The sound varies in loudness.  It comes and goes, but has been constant in recent weeks.  The noise is usually drowned out by engine and wind noise above about 45 mph.  It seems worst when the vehicle is run the first time in a day, or after a long (over 1 hour) drive.  The noise varies with vehicle speed.  The noise comes when the car is moving in forward or reverse, regardless of the terrain, in or out of gear, whether the differentials are locked or not, and even coasting with the engine off in the driveway.

There is no change in the handling of the car.  It does not "grind" me to a stop.  I cannot see anything visibly wrong with anything under the hood or under the car.

On an unrelated note, what's the best way to clean 12 years of crud and VSLCF's (very slowly leaking congealed fluids) off of my engine?  I'm wary of Gunk.

Thanks,
Dewey Scandurro (scandurrodm@arlaw.com)
Baton Rouge, Louisiana, USA