1993 Ford Escort LX Wagon - Speedometer issue

I'm hoping someone may have some knowledge of this problem, or at least some ideas before I start digging into it. More often than not the speedometer on this car will make a loud clicking noise and begin jerking around like crazy. However, the odometer will still count off miles correctly, or at least appears to be. I may be wrong, but it seems like if it was the speed sensor, or a cable, the odometer would not work. Any ideas? Thank you in advance.

Update for anyone interested: I went ahead and dug into it.

This particular car has a speedometer cable.....I removed the cable from the transaxle so I could pull the instrument cluster, and then removed the speedometer from the cluster.

To see if I could re-create the problem, I connected the cable back to the speedometer and then connected the other end to a variable speed drill. I set the drill to it's lowest speed setting and turned it on. (speed showed around 15MPH).

Right away I could see a problem with the shaft/wheel that connects to the speed indicator needle. It looks like some sort of clutch setup. Anyway, there is a lot of slippage in it, especially the more I increased the speed.

I can't see where you can really make any adjustments to this clutch, so I am going to go to the salvage yard to find another.

Also, after some further research on this and other forums, it seems that this was a common problem with the 85MPH speedo from around this model year. (However, I could not find a TSB from Ford that addressed it). So I think replacing should solve my problem.