[R.L.]

Originally Posted by raycow

If it is a C-10 you probably have a 3.73, but there is no need to guess about it.

Jack one rear wheel off the ground, put the transmission in neutral and the parking brake off. Put matching marks on the pinion yoke and differential housing. 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

Thanks Ray