I needed to replace the pinion shaft (part that connects to the ujoints at the rear of the driveshaft...so everyone knows what I mean). I got the old one off, put on a new one (and new seal) and now the rear gears are howling like crazy. When I accelerate, they are quiet. When I'm off the gas or rolling in neutral, it's whirring and howling. Sound level is directly proportional to speed...more MPH = more howl. I'm worried a bearing or something is pinched or ??? Gears / axle was 100% OK before replacing the part (no noise at all - needed to replace it because a corner where u-bolt tightens down on u-joint was cracked, and rewelded by previous owner). :: ANY IDEAS ?!?! I'm scared to drive it.