sorry should have said it was a 36-70-2300 and its a converted cen matrix tr i started out with 13/46 but noticed that the gear mesh was wrong due to the motor mount the screws were over as far as i could no way a 12 or 11 tooth pinion could be used only way i could use anything smaller is to change the spur gear to a 50 tooth maybe? thanks for the help so far!!!!