I've got a 1991 R1500 Suburban with a 10 bolt rear axle. The pinion seal leaks and recently I've noticed some vibration at low speed under high acceleration. I thought some u joints might be going bad, but as I was down under the truck pulling back and forth on the driveshaft I realized the pinion yoke could move back and forth just a little. Do you think I could just pop on a new pinion seal and tighten up the nut some or are the pinion bearings shot and the whole thing need rebuilt?