Mismatched Diffs

[KANTANKRUS]

I was informed that I could run, mismatched differentials, as long as the front diff was, for example 3.07 and the rear diff was 3.73 is this true?

[cruiser54]

Not at all.

[Eagle]

Definitely not. Too much mismatch.

 

Because not all axles have the same size ring and pinion gears, there are combinations where the front doesn't match the rear perfectly -- at the second decimal place. In the XJ and MJ, for example, you'll actually find a 3.07 axle mated with a 3.08, and a 3.54 mated with a 3.55. Those are close enough to work. But 3.07 with 3.73? Nope!

[HOrnbrod]

If you ran different tire sizes front and rear it would work w/o generating much diff-killing heat. For example with a 3.07 front ratio axle w. 27" tires and a 3.73 rear ratio axle w. 33" tires, calculated engine RPM would be 2483 RPM vs. 2469 RPM, a difference of only 14 RPM. I think you could run forever with no problems that close....

 

Would look funny though unless it was a gasser..

[omega_rugal]

1 hour ago, HOrnbrod said:

If you ran different tire sizes front and rear it would work w/o generating much diff-killing heat. For example with a 3.07 front ratio axle w. 27" tires and a 3.73 rear ratio axle w. 33" tires, calculated engine RPM would be 2483 RPM vs. 2469 RPM, a difference of only 14 RPM. I think you could run forever with no problems that close....

 

what he says...

[KANTANKRUS]

Not gonna happen. I plan to either convert the front diff to 3.73 or both axles to 4.10, running on 33 inch tires.

 

[HOrnbrod]

3 minutes ago, RestoringNV said:

Not gonna happen. I plan to either convert the front diff to 3.73 or both axles to 4.10, running on 33 inch tires.

 

 

Err, good plan.

[Eagle]

Of course, as long as you leave it in 2WD you can run mismatched ratios. Most folks doing that remove the front drive shaft just to ensure that nobody accidentally engages 4WD and grenades a transfer case.