i had this problem, too, and decided that it was caused by an angular
misalignment of the axis of rotation of the cable with the piece that it
mates to in the socket on the back of the spedo...  if the cable enters
the spedo at an angle, this will cause the speed at which the gear in
the the gauge is driven to be faster during part of the rotation and
slower during the opposite part, hence the bounce (this same phenomenon
is why a universal joint is not a constant velocity joint).  i think
this also wears out the bearings in the gauge eventually because they
aren't designed to take that side loading.  i replaced my spedo cable
because i thought the plastic fitting on the end that clips to the back
of the gauge was loose, allowing the cable to enter at an angle.  the
problem went away for many months but it just reaapeared when i took the
instrument cluster out to put some new lights in.  i guess i'll try
reaching in and moving the cable around while i drive and see if i can
get it to dissapear again.

Ben.

Tim King wrote:

>Hi -- I know I've seen references to this, but can't find anything. I have an 87 syncro with a bouncy speedometer needle. I've actually replaced the speedo with a Jetta unit and I get the same bounce. I think that isolates it to the cable(s), or possibly the gear in the syncro front diff.
>
>I've pulled the cables, test spun them with a drill, cleaned them out with brake clean and compressed air, and then lubed them up with nice bike lube (white lightning). So far, this makes no difference. Any tips on getting rid of the bounce, or at least isolating it to one cable?
>
>Thanks
>
>Tim in Seattle
>87 Syncro Westy/Suby 2.5
>
>
>