i suspect that gm or getrag made a major change to the pinion seal, as they also changed the pinion yoke also--what i would like to see is a side by side comparison of the old parts verses the new ones---i've always suspected a problem where the pinion yoke attaches to the driveshaft causing an unbalanced condition,thereby prematurely wearing out the seal--my guess is by redesigning the pinion yoke and beefing up the seal ,it cures the problem