Rearend diff question.

[GobbleStalker]

Is there any way to tell the gearing in the rear end without taking it appart. Also I do not know if it is posi or not. Truck is running but not well enought to burn the tires. Motoer getting ready for a rebuild. Any help is appreciated.

Thanks
Kev

[ChevLoRay]

With it jacked up, or on a rack....mark a reference point on the tire (or remember where you started)..then turn the tire one full revolution while you count the number of times that the rear u-joint turns. If the tire turns one time and the u-joint turns just a hair over 4 turns, it's probably a 4.11.

[jcis4me]

So if the drive shaft turns 3 times? 3.08?
Thanks
Marty

[raycow]

Close, but no cigar.

Put matching marks on the pinion yoke and differential housing. Jack one rear wheel off the ground, put the transmission in neutral, and the parking brake off. Turn the wheel exactly TWO revolutions and count how many times the driveshaft turns, estimating any fractional turn as closely as possible. That number is your axle ratio.

If the wheel is difficult or impossible to turn, you may have posi. In that case, jack both rear wheels off the ground and turn either of them only ONE revolution. Count the driveshaft turns the same way as for an open rear.

Ray