12 Bolt Pinion Bearing Pre-Load

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TJ805

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When I went to change the pinion seal, the pinion nut was finger tight. I planned on using my torque wrench to get an idea of where it was at, but now have to guess. Wheels are on the truck and I have no plans to remove them or the axles. I'd like to get it as close as possible for the time being. What would you do?
 

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Let me start by saying I am by no means an expert. I assume others will chime in.

I did just finish rebuilding the GM 12-bolt in the 77K10. I did a lot of research to educate myself. So from that I would offer the following.

First, the pinion nut is supposed to be a lock nut. And it is not to be reused once removed. It must be replaced. Otherwise I expect the result will be what you found - a loose nut. So regardless of what you plan to do moving forward, I would get a new one on order.

Second, unless your 12bolt has been converted to eliminate the crush sleeve, then it has a crush sleeve. This means you will not be able to (re)achieve the pinion pre-load again without replacing the crush sleeve. And even with a new crush sleeve, achieving the right pre-load is a bit tricky - especially for us not experienced doing it every day. It is not uncommon to go thru several of them before hitting spot on and not over-torquing (ask me how I know that).

But again, I am clearly not an expert. I would be curious to read what the service manual calls for with a pinion seal replacement. Do they require the crush sleeve be replaced? Just a new lock nut?
 

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Thanks for the info. I'm am aware of all that you said. I don't see myself replacing the crush sleeve or converting it. Just hoping for a suggestion on how to get it close. If anyone has had a similar situation, please let me know.
 

TJ805

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Let me start by saying I am by no means an expert. I assume others will chime in.

I did just finish rebuilding the GM 12-bolt in the 77K10. I did a lot of research to educate myself. So from that I would offer the following.

First, the pinion nut is supposed to be a lock nut. And it is not to be reused once removed. It must be replaced. Otherwise I expect the result will be what you found - a loose nut. So regardless of what you plan to do moving forward, I would get a new one on order.

Second, unless your 12bolt has been converted to eliminate the crush sleeve, then it has a crush sleeve. This means you will not be able to (re)achieve the pinion pre-load again without replacing the crush sleeve. And even with a new crush sleeve, achieving the right pre-load is a bit tricky - especially for us not experienced doing it every day. It is not uncommon to go thru several of them before hitting spot on and not over-torquing (ask me how I know that).

But again, I am clearly not an expert. I would be curious to read what the service manual calls for with a pinion seal replacement. Do they require the crush sleeve be replaced? Just a new lock nut?
How much slack was in your yoke after you set your crush sleeve? When I line up my marks I can pull/push the yoke in and out about 1/16". One more revolution is way too tight...
 

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What did you end up doing?
 

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When I went to change the pinion seal, the pinion nut was finger tight. I planned on using my torque wrench to get an idea of where it was at, but now have to guess. Wheels are on the truck and I have no plans to remove them or the axles. I'd like to get it as close as possible for the time being. What would you do?
If you have already overtightened it,and I am sure that you have. There is no getting close or guessing. Once the crush sleeve is crushed too far its too late. You have to remove the crush sleeve and replace it,or at a minimum cheater,backyard you can use a hammer and a piece of pipe to try to stretch some of the crush out,but getting preload is done with the differential out. So unless you are going to do it right the only thing you can do is use an eliminator kit and go for zero movement then go a couple of thousands thinner it won't be right but won't be horrible. Or take some of the crush out of the crush sleave,reinstall it tighten it until you have no in and out movement then tighten it a tiny bit more..Checking where with your torque wrench in the beginning would have you no good anyway.
 
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The way we used to do them in the shop is to count the threads showing and mark the nut. Install it with the same threads showing and mark in the right place.

I have seen guys just remove the nut with an impact and put it back on with a quick shot on the impact. Not the right way of course but they never came back with issues.

You should just shut up the nut at this point and don't over think it. Don't get me wrong proper preload is important but it is not as critical as it is made out to be. The only way to fix it now is to take it apart. If it was me I would not bother. If it is too tight you will end up with a bearing noise and then you have to replace them. Most likely you will enjoy years without issue.
 

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The way we used to do them in the shop is to count the threads showing and mark the nut. Install it with the same threads showing and mark in the right place.

I have seen guys just remove the nut with an impact and put it back on with a quick shot on the impact. Not the right way of course but they never came back with issues.

You should just shut up the nut at this point and don't over think it. Don't get me wrong proper preload is important but it is not as critical as it is made out to be. The only way to fix it now is to take it apart. If it was me I would not bother. If it is too tight you will end up with a bearing noise and then you have to replace them. Most likely you will enjoy years without issue.
He already overtightened it ,which would would crush the sleeve more. He says on his second post " I tightened it 1 turn more,but that was way too tight" that tells me an already crushed crush sleeve has now been crushed some more and too much. If he hadn't given it that last turn I'd think things could be fudged but once you've gone 1 turn too many you can't just loosen it backup.
 
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Ricko1966

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Okay I just thought of something I would try. I'd back the nut off until I had in and out play. Tap the pinion in with a block of wood and a hammer,now pry the pinion out using the yoke and pry bar. Measure that distance,use a dial indicator or a fixed reference and calipers,feeler gauges whatever. That is the amount your crush sleeve is crushed too far. Get a shim,washer whatever a little thicker. Pull the seal and front bearing put in the shim,replace the bearing,seal and yoke. Tighten the nut until all play is gone then,another 1/8 turn or so. Now you will have zero play and some preload. Clean the end of the nut and pinion shaft and put a drop of thread locker on,wicking preferably,but I've used red as wicking without issues.you may be able to buy shims from Yukon or one of the other companies that sell crush sleeve eliminators.
 
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@Ricko1966 some larger diameter soft solder cut and made into a ring could be used in between the crush sleeve and pinion to determine a shim thickness. Tighten until desired preload achieved, tear down and mic solder and choose appropriate shim. Of course, exact shim thickness is not that important if being used with a crush sleeve, just thicker than the over crushed amount.

People also do the solder trick to get a base reference for a crush sleeve eliminator or shim type pinion. Pretty clever idea.
 

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@Ricko1966 some larger diameter soft solder cut and made into a ring could be used in between the crush sleeve and pinion to determine a shim thickness. Tighten until desired preload achieved, tear down and mic solder and choose appropriate shim. Of course, exact shim thickness is not that important if being used with a crush sleeve, just thicker than the over crushed amount.

People also do the solder trick to get a base reference for a crush sleeve eliminator or shim type pinion. Pretty clever idea.
Yep my first thought, and actually started writing it as using a solder ring,then it occurred too me it's a crush sleeve as long as I find the gap I can make up the rest with the crush sleeve. No need to assemble and disassemble for the solder. I've also used solder to check deck clearance on assembled engines.
 

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6 year old thread guys and the OP hasn't been back in a couple of years.

I've done a bunch of pinion seals. Throw out the Chiltons manual with this one. Pop the yoke off and replace the seal, tighten the nut by hand until you hit the crush collar. Add a 1/4 turn with all your might. Replace the nut or stake it with a pin punch a few times. Go racing.
 

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6 year old thread guys and the OP hasn't been back in a couple of years.

I've done a bunch of pinion seals. Throw out the Chiltons manual with this one. Pop the yoke off and replace the seal, tighten the nut by hand until you hit the crush collar. Add a 1/4 turn with all your might. Replace the nut or stake it with a pin punch a few times. Go racing.
It was too late for O.P. to do it that way. Good catch on dead thread resurrected. On the brightside maybe others will read this before they make the same mistake.
 

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