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raycow · 08-06-2010, 02:09 PM

A GMC would have a Dana 44, which has much better parts availability than the old Chevy rear. Most of these were not geared as low as the Chevys. I have seen them with 3.07 and 3.54.

There is no need at all to guess about the ratio.

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

08-06-2010, 02:09 PM	#5
raycow Registered User Join Date: Mar 2003 Location: San Francisco, CA USA Posts: 2,454	Re: Rear End A GMC would have a Dana 44, which has much better parts availability than the old Chevy rear. Most of these were not geared as low as the Chevys. I have seen them with 3.07 and 3.54. There is no need at all to guess about the ratio. 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