heres the truck specs. 1982 k5 14 bolt swap 6" lift double cardon high angle driveshaft. the shake: its a left to right feeling out of the rear of the truck. its not through the steering wheel at all. at 50ish mph it is at its worse and smooths out out (but not all the way) around 65ish mph. sounds like a balance issue right?? before the 14 bolt swap there was no shaking, so that eliminates the driveshaft being a source....but maybe not the pinion angle. right now my pinion points DIRECTLY to the tcase tail shaft. I used a 6* shim to make this happen. my first thought was maybe taking out the 6* shim and using a 4* shim. im thinking maybe underload, the springs are soft enough to change the pinion angle enough to cause the shake....just a thought im using balance beads. I have used them for years....8oz per tire per manufacturer. the driver rear only has 4 oz in it however. the order was wrong and I haven't received my corrected weight in the mail yet...but could only 4oz cause this much shake ??? also, I believe it from the shaking, I have developed a pinion seal leak. blahhhhhh. so if anyone has advice on replacing the pinion seal I would love to hear it. is it a good idea to replace the pinion bearing as well? thanks in advance.