The Stovebolt Site Forums The Shop Area Driveline speedo / trans

in my 1951 chevy 3100 all origonal (3 on the tree) my speedo is not workin the speedo head is fine i rebuilt it and the cable is fine i put a drill on the end of the cable from off of the tranny and ran a drill, the speedo works and cable works, now i removed the gear nut from the tranny and the squair part is good and the gear at the end is fine too, the gear inside the tranny that drives this unit was not visable so i put my finger in there and i could spin the gear inside the tranny (the tranny was in N) now i am not sure what the problem could be as to why the speedo is not working?? unless the gear on the inside is stripped although it did not feel stripped??

I would guess that your problem is with the transmission gears. You shouldn't be able to turn the gears in the transmission if they are good and in mesh. The drive gear is hooked to the output shaft of the transmission and should only turn with the output shaft.
Hope this helps
Jim

The front U' joint yoke has a bolt that holds the yoke on. This also pinches a spacer, speedo drive gear, and a spacer pipe between the rear trans bearing and the yoke. The gear is free floating unless pinched between the two spacers.
All this to say the bolt is loose so the drive gear is spinning on the shaft.

Here is a breakdown of a car transmission but the truck is the same. Link to parts book illustration (see 4.345 spacer, 4.337 gear, and 5.579 spacer/pipe).

You will need to split the U' joint to tighten the bolt.

One thing to watch for is, if the bolt has been loose for a long time the spacer pipe will wear on it's ends. When this happens tightening the bolt will not be enough to pinch down on the spacers and gear. Instead the washer in the center of the yoke will bottom out on the end of the shaft.