'86 speedometer stopped working

[BobCT]

I have an '86 Turbo which I just bought. The odometer stopped working so I assume that will be the gear. In the little bit that I've driven it, the speedo wouldn't start working until I hit about 30 MPH or I smacked the top of the dash. Now that's stopped altogether.

For now, I'm assuming the issue isn't at the transaxle end since a dash smack brought it to life. When I replaced the cluster bulbs, I cleaned up the footballs but they really didn't need it. I've gone through and cleaned every ground connection on the car. While I'm replacing the gear, is there anything else electrically in the cluster that might cause this issue other than a bad speedometer? Are cold solder joints an issue? Should I try and run an additional ground? My temp gauge does "bounce" a little when I hit the brake pedal.

Trying to figure what my speedo issue is while I have the cluster removed.

thanks
Bob

[944 Ecology]

While a disintegrated odo gear is the usual cause, it can also be a bad stepper motor, or a bad circuit board.

The speed indicating subsystem usually does not have problems, except for broken mounting pins (when trying to remove the pointer and mount, which is necessary to replace the odo gear).

I have not encountered cold solder joints in 10 years of working on these. However, some cannot be revived after a ham handed mechanic or DIYer has caused damage.

A bench test is the best way to test, as opposed to multiple removal/replacements in a car.

I repair these as a side hustle, and have great success in doing so.