This is a common VW problem. It is caused by a combination of two things.
1) questionable design, 2) resetting the trip odometer while the vehicle is
in motion.

I have had four separate vehicles "do" this, prior to learning about the
trip reset issue. I have never had 100% long-lasting success in any repair
with the original gear, as it gets wallowed out quickly when the shaft
spins inside it. There was a source in San Diego a year ago who had a dozen
of these gears...some help now, huh?

The most lasting fix I have done involved removing the gear, abrading the
shaft so it had some "tooth", cleaning all with electronics cleaner,
applying a small amount of epoxy, and shoving the gear back on. Let harden
12 hours, carefully reassemble. Lube with a VERY scant amount of axle
grease.

Then NEVER reset your trip odometer unless the vehicle is completely
stopped. Reason being, when you press the reset button, it forces certain
parts to de-mesh and get out of synch.  Consequently, the main odometer is
temporarily locked, unable to rotate. That little white gear, however,
continues to be driven by the worm gear, so it breaks its grip on the main
odometer shaft, and is forced to free-rotate on the shaft until you release
the button.

Cheers.
G. Matthew Bulley
Director
Bulley-Hewlett & Associates
www.bulley-hewlett.com
Cary, NC USA
888.468.4880 tollfree

-----Original Message-----
From:   Bill Johnson [SMTP:bjohns@DTX.NET]
Sent:   Tuesday, October 05, 1999 8:24 PM
To:     vanagon@GERRY.VANAGON.COM
Subject:        Odometer fix

I have my Speedo out of my '82 and found the little white gear
that is engaged by the worm gear had slipped off it's shaft.
Put it back on and it looks like it will work, but it also looks
like it will slip off again.  Are there any suggestions here.
What type lube should I use in the Speedo, if any?

The back case of the Speedo is disintegrating.  It looks like I
will have to tape it up.

Bill