Mechanical speedo stoped turning at 47530

[Guest]

Hello, I have a 1985 Limited that runs great, but the mechanical speedo stoped working. It's winter now in Wisconsin so I thought I'd tackel the job of replacing
or rebuilding. After I removed the speedo unit I found the mechanical parts in good working, thought I'd see the plastic gears ground. A little background, all other aspects of the electric speedo and tach work perfectly, as well as the digital computer. Now to my question, is they a way to test the drive motor?
Or is it possible for the drive motor to not receive power when all other electric parts are working?
Thanks for any help