The Stovebolt Site Forums The Shop Area Engine Shop What is rear end gear ratio?

The year and model of your truck is a good place to start in terms of figuring out what the gear ratio is. Then you can look in the shop manual at the chart showing gear ratios for different models.

The method suggested in the thread posted by Joker might be difficult to implement if you've got a torque tube rear end. The way to do it with an open driveline is to count the number of drive shaft revolutions it takes to get the tires to go around once. Usually you work with 10 revolutions of the tire and move the decimal point. However, since in a torque tube (aka closed driveline) you can't see the drive shaft is turning that way won't work.

If you do it by pulling the cover to the differential you would count the number of teeth on the ring gear and the number of teeth on the pinion gear and then divide. Many times the ratio is stamped into the ring gear in that format- 11 pinion teeth and 41 ring teeth = 3.72:1. The ring gear would be stamped with several numbers including 11 (space) 41.