drive ratio

[ftwflh]

Is there an easy way to tell what gears you are running?

 

[CJ]

Jack up the wheels off of the ground, rotate a wheel in the forward direction. If the other wheel rotates in the opposite direction you have an open differential, if it rotates in the same direction you have a Limited slip diff.

For Limited slip diffs, count the number of times the axle turns - that is your gear ratio. Example, the axle turns 3.75 times to the wheel - you have a 3.73 diff.

For open diffs - you have to divide by two. The ratio is still the same. The axle will rotate twice per wheel revolution.

 

[derf]

I usually just check the tag on the differential. If there's no tag, it's probably been modified.

In that case, I will lift both rear tires off the ground, put it in neutral, and spin the driveshaft. Count the number of times the driveshaft has to spin to get the wheels to make one complete rotation. With both tires off the ground it doesn't matter what kind of differential you have, it will spin the tires the same.

About 3 = 3.07. Just over 3-1/4 = 3.31. About 3-1/2 is 3.54. Around 3-3/4 = 3.73. Just over 4 = 4.10. And 4-1/2 = 4.56. Those are the common gears for Jeeps.


****Shameless plug**** Another way to figure it out is to have a tachometer telling you your RPMs at a given speed and you put in the numbers in a gear ratio calculator like mine: Gear Ratio Calculator