I would investigate your CVs .  There are two on each side on the rear axel.
I had barely audible thumping last summer that developed into horrendous
banging over a three week period.  Test it out by turning in a parking lot
one way then another.  Also, note the difference when going up a hill and
then down.  If the noise intensifies going uphill, it's probably the CVs.
The ball bearing have worn out with flat sides on them.

Cheers,

DJL
----- Original Message -----
From: Bradley Flubacher <flubach@HOME.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, April 12, 2001 9:31 PM
Subject: disturbing thumps (Transaxle?)

> I've been hearing a thump.  I think it's my transmission.  I just got this
> 4-spd from a 90 vanagon at the auto salvage yard. Anyhow, this is what the
> conditions are:
>
> I hear a thump, thump, thump when I'm in third gear an accelerating. Only
in
> third gear.  The frequency of the thump seems to be about 1 per-sec at
> around 40 MPH.  It is not thumping as fast as the engine is turning, nor
as
> fast as the wheels.
>
> Any thoughts?  I guess I should get ready for a rebuild? I have a core
> sitting in my garage with the broken 3/4 slider problem, now this.  I'd
love
> to be able to trade them both for one good one.
>
>
> Bradley Flubacher
> State College, PA
>