I just had my rear end rebuilt last month with gm 3.73's after I broke my Richmond Pinion gear. I have been gentle with it over the past 450 miles as instructed, no launching, normal speeds. I took it out for a spin the other day and noticed when I hit about 80-90 I start feeling a mild vibration and if I take it over 100 it's vibing really bad. Before I broke the gears I've had it burried past the 150 speedo with NO vibration what-so-ever. What's the problem?? I'm gonna hollar at the dude who rebuilt it this week. I had a whole new Master bearing kit put in, changed axel bearings and everything. What could be the problem???

 

It could be several things. Could be the driveshaft bent or not balanced, could be the U-joints about to give up, could be a new pinion bearing not properly pre-loaded or even a bad transmission mount.

 

I know its a pain, but you may also want to check the axle shafts for wear from the original bearings. Over time the bearings will wear grooves in the axles...sometimes when you just replace the axle bearings with stock replacements youll get a little noise and some vibration...They make axle bearings that are slightly offset that position the bearing over a virgin axle surface and this eliminates the problem...Your rebuilder may have have done this already, but he should have told you if you had grooves worn from your old bearings...or, if they are grooved, you could buy new axles...Mosers, etc...$225-250ish... good luck...
--Alan

 

I went to the shop to inspect the work while it was all torn apart. The axels are fine, & all new Timkin Bearings from the axels on in. When the old pinion spline let loose it got wedged behind the pinion gear and the case for about 1/8-1/4 mile before I stopped and it fell down. It chewed up the case where the pinon gear enters but the damage was minimal.

The vibes aren't slight, They increase in intensity with higher speed, once I'm over about a hundred or more and let off the gas it is a rythmic vibration, low rumble sound, not a clunking or whining associated with incorrect setting or tranny mount.