Any way to tell differential gear ratio without removing the cover?

[hrbergeron]

Is there any way to tell what gear ratio the differentials are without dropping the covers? I thought they were stamped on the side, but I can't find it. This is on a 1994 M998A1. Need to know the ratio for programming my transmission computer.

 

[gringeltaube]

With the TC in N, and wheels chocked.... jack up one wheel, then turn the other one 1 full revolution while counting the number (and fraction) of turns the drive shaft made.
That number, times two, is your ratio.

If you have a 2.73:1 ratio, your drive shaft will spin exactly 1.365 turns. Or 360⁰ plus another 131⁰.
For more precise results, turn your wheel 10 revs and then divide by 5 the number of drive shaft revs.


Note: Just in case, better do this on both, front AND rear differentials. We have seen cases of mismatched ratios, already...
See this thread...

 

[Retiredwarhorses]

Easier is too tell what model year the truck is...
85-94 A0-A1 have 2:56
all A2’s have 2:73
ECV on up, 3:08