12 bolt set up

[bdl1503]

I am new to this forum and have a question, anyone know of anyone in the central Ky area to set up a 12 bolt? I broke the carrier housing and spiders in mine and after much reading and studying I ordered a new posi unit, ring and pinion and put it together myself. Seems to work fine with no whining but I have a vibration, really bad around 55-60mph. I feel confident its something I have done because it wasn't there prior to breakage. Any suggestions on a good person to straiten it out would be appreciated.

[demian5]

Could it be your driveshaft?

[bdl1503]

Yeah anything's possible, Im just going with the law of averages that I used the same driveshaft and marked it and the yoke before I took it out they are oriented the same as they were but with the new pinion I guess its not 100% same as it was.

[Oydllay]

Make sure the caps on the rear joint are located properly. Ive seen many people not put the retaining rings on the caps in the yoke. Also seen the locator tabs worn or missing on the yoke if you have that style. See if the shaft will move side to side in the yoke from clearance between caps and trunions. Should be fairly tight. There's not much you can do to make the differential vibrate. The ring gear turns much slower than the pinion. Ive never seen a pinion Out of balance either. It's a machined part with little runnout variation.

[bdl1503]

Okay Ill double check all that stuff to make sure, so am I understanding you to say that vibration is probably not a problem with the setup? I was a bit concerned about the crush collar I had never fooled with one and didn't feel comfortable messing with it.

[Oydllay]

The crush collar is exactly that. You use it to maintain torque on the nut while setting the preload on the bearings. More simply put, if you leave the collar out you can turn the nut until you draw the bearings up into the races and take up the slack. You could then turn it just a little more to set the preload. At this point the bearings are snug but the nut is only hand tight. It has nothing to torque up against except the bearings. If you pinned the nut somehow in this position, you wouldn't need the crush collar. The nut would be mechanically locked and couldn't back off. Now put the collar in. The nut will spin easy until it tightens up against the collar. This should happen before the bearings get tight. Now you have to ram the nut with enough force to crush the collar. As you cram the nut more, the collar flattens out allowing the bearings to draw together and snug up ,all the while giving the nut something to torque against. When you get to the proper bearing preload just stop. The nut will already be torqued. I like to use gear lube on the old nut and threads during the initial tightening as it makes it easier to crush the collar. When I get close to taking all the bearing free play out I back off the nut, clean the threads, apply locktite and install the new nut. Bring it up snug and then slowly (preferably with a strong air gun) bring it the rest of the way to proper preload. Done.
If you didn't crush the collar enough to take the clearance out of the bearings, your pinion may be flopping around. Grab the yoke and see if it moves in/out or up/down. When the preload is set correctly it takes about 20 INCH pounds to rotate the yoke or turns with some resistance with one hand holding the yoke with your fingertips.

[bdl1503]

Alright, thanks for the info I believe I torqued it to 15"/lbs so I'll look at all that again. I'm gonna try to get it on the lift next couple days and recheck everything.