OZ951

I have picked up an early 85 model 944 N/A, it has a speedo problem that is a bit annoying - the speedo needle will indicate the correct speed for a second or so and then click and drop towards zero, moments later this situation will repeat and continue to repeat as long as the car is driven.

This particular car was off the road for more than 12 months due to a blown transmission. It now has my spare transmission in it. I have noticed that the ticking has reduced slightly the more I drive the car (its only been on the road for a few hours at this point).

Has anyone else seen this problem and know of the solution? My search of previous posts hasnt showed up any info on this problem, so I thought I would pose this question before I start pulling things apart.

Cheers
OZ951