Geez, You should've said that before.

h:
So your speedometer works but ONLY in 5th gear? Correct?
Do you drive it normally like say from 1st to 5th gear? And then the speedometer works? Or just throw it in 5th gear?
Thats very strange. You almost get power to the wheels because your speedometer gear on the differential is turning.
Yes please keep me updated.