truck 12 bolt crush sleeve/pinion preload - Hot Rod Forum : Hotrodders Bulletin Board
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Old 12-04-2013, 08:41 PM
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truck 12 bolt crush sleeve/pinion preload

After the long process of shimming the pinion for a proper gear pattern I am finally doing final assembly. The problem I am having is getting preload on the pinion bearings. I have done a few rear end rebuilds including this truck 12 bolt before, but never had an issue with getting pinion preload.

Here is how the process went:

First of all, when I was assembling and disassembling for gear pattern checks I used the old bearing race as a spacer, some thick washers I had laying around, and the old nut to tighten up the pinion in the bearing races instead of using the yoke. I had no problem getting bearing preload this way, which was not surprising. Then final assembly came. I installed the crush sleeve, bearing, and then the new seal. Next came the yoke, washer, and new pinion nut. It took a while, but I was able to cinch down the crush sleeve to take up all the play in the bearings with a 1/2" impact. I would measure the pinion preload and it seemed to have a high breakaway torque with about 10 in.lb while rotating. I was shooting for 13-15. I did some short burst with the impact and kept checking and the preload never went up, it actually dropped to about 8 in.lb. Wondering what was going on, I took the nut off and all I really noticed was that there was not much further for the yoke to slide onto the pinion before the washer would be touching both. In fact, they may have been, but it is hard to tell. I then put it back together, used a 3/4" impact and got it to turn another 1/8 of a turn before it stopped. The strange thing is that I now have very little preload. It is now less!

Anyone ever heard of something like this or have any thoughts/suggestions?

Do I try even more torque on the nut somehow? An impact has worked on the others, but this is definitely the tightest one I have done. What do you think I could do to get some more room for the yoke to slide down the pinion? The yoke is a Spicer with 1350 u-joints. It took some searching to find a seal that would work with this yoke.

Thanks in advance for any replies.

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Old 12-05-2013, 06:11 AM
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Are you using the original extra thick washer behind the pinion nut, or are you using one of the thinner washers that come in some installation kits and with some yokes? If you have one of the thin washers then toss it in the trash and get the correct washer. You can get them from Tom's differentials. The thin washers bend when you put that much torque on them and they can sometimes allow the bearings to lose their preload after you start using the rear end. This can cause a complete rear end failure.

I'm guessing that this is a 8.5 10 bolt yoke and you had to use the pinion seal from the front axle of a late '70s to early '80s GM 4X4 truck with the 8.5 front axle. This is a comon swap, but the yoke should have worked fine. You might have to use a spacer between the yoke and the outer pinion bearing. A 1/16 to 1/8 inch spacer should be more than enough.
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Old 12-05-2013, 09:06 AM
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Could you have stripped the pinion nut? I have had a few of the aftermarket nuts blow the threads out when trying to torque them.
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Old 12-05-2013, 03:13 PM
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I am still using the original 1/4" thick washer. The spacer between the bearing and the yoke sounds like a good idea to try. I'll have to see if I can find something that will work. Anyone know where I might find something?

I'm thinking the nut is fine, but I will check. I may get another nut anyway because I have put it on and taken it off a few times.
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Old 12-05-2013, 04:39 PM
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If you have a local vocational school with a machine shop have them make a spacer for you. Make the OD about .005 smaller than the OD of the yoke where it runs in the seal and make the ID about .005 larger than the pinion shaft. I would make it about 1/8 inch thick. Be sure that the faces are parallel with each other. You don't want it slightly thicker in one place and thinner in another.
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Old 02-20-2014, 08:38 PM
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Well, its been a couple months now but I was able to verify that the washer was touching the shoulder on the pinion and so I could not get it to tighten any farther. I simply ground down the shoulder of the pinion a little bit and I was able to get the preload I was looking for with a 1/2" impact. Jusy wanted to let everyone know how it turned out. Thanks for the replies.
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