to get the ratio, put the rear up on jacks, and take the wheels and drums off. Spin the drive shaft, and verify the axles rotate together. Make a mark for 'top' on the pinion and one of the axles. Start spinning the pinion with a helper watching the axle. Keep count of the turns until your helper tells you the axle has returned to its start mark ( exactly ) Compare numbers with your helper and do the math to reduce it to a ratio.