Sean,

I've had to fix similar odo problems on my VWs from '78, '86 (two), & '87 - 
same problem in each case.

The VDO used a die-cast zinc drive gear that drives the disk stack. This gear 
is press-fitted onto a perfectly smooth drive shaft. While zinc can be cast 
very precisely, it is also known for its tendency to "creep" or yield even 
under low loads.

With time (and probably our high US temperatures - Germany stays cooler than 
even the northern US) the zinc gear relaxes and starts slipping on the drive 
shaft. I noticed it usually would stop working first on hot afternoons - then 
progress to more random behavior, and finally complete failure.

I've cured all mine by taking the odometer apart and using a machinist's 
center punch to make a few "dings" on the shaft right under where the zinc 
gear fits. The light dings raise enough material to act like a slight spline. 
Then reassemble and carefully press the zinc gear back on so it doesn't bind. 
(Then there's the matter of getting the speedometer needle back in the right 
position......)

After doing this I've never had another problem. (With the odometers at 
least!)

Likely another case where our severe US climate is outside the German design 
parameters. (If only they wouldn't act like it's our fault.)

Tom Brunson

>Hey all,
>Well, it started yesterday.  My odometer is getting weird.

>The situation:

>Driving to Knoxville TN from Johnson City TN I notice that the trip
>odometer has been on 9.9 miles an awfully darn long time.  I notice that
>the odometer is not advancing but the speedometer is working fine.

>At a rest stop, I push the reset button on the trip odometer.  The trip and
>regular odometers now work fine.

>Sometime on the way back, it stops working again.  I reset it this morning
>when I noticed it had stopped and it starts working again.  Then it stopped
>again, and then I reset it again and now it's working.

>There is no noise being made by the odometer.  The speedometer works fine. 

>There is no real rhyme or reason to when the odometer cuts out.  Once it
>stopped at 9.9 miles, once it stopped at 190 miles, once it stopped at .7
>miles.

>Any ideas?  Is this possibly related to the oh-so-common plastic drive gear
>cracking problem?  It looks like my time has come.  

>I will eventually pull it apart (when I get some free time, could be a few
>weeks...) but I'd love to hear any ideas in the meantime.

>thanks,
>Sean