12 bolt problem

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JuicedBu
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12 bolt problem

Post by JuicedBu » Mon Mar 12, 2007 10:02 pm

Posted: Tue Mar 06, 2007 7:07 pm Post subject: 12 bolt problem

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I'm installing gears in a 12 bolt in a 70 Chevelle for a buddy of mine. I've done a ton of installations and have never had this happen before. I put the pinion in and tried to tighten the nut but wasn't able to set preload. No matter how much force I put on it it wouldn't go. I took the nut off and noticed that top of the splined on the pinion sits flush with the splined area on the yoke. It almost seems like the yoke needs to be taller. Has anyone ever ran into this problem before? If I can't get a longer yoke, I could always have a shim machined up. I would only need it to be about 1/8 of an inch. When I say the yoke needs to be longer I mean the area that is splined on the inside and where the seal rides on the outside.

The other problem I'm running into is that the pinion seal I have doesn't seem to fit properly. It is recessed and sits too low. It rides on the very edge of the yoke and is going to leak.

Maybe the two problems are related. This rear end has fought be from the very begining. First, half the cover bolts were rusted on. Then, the old pinion nut was rusted on and I had to cut it off. Then, the axle bearings didn't want to come out. I didn't spend much time looking at it but in the short time I did I came up with a few possible fixes. Get a longer yoke (if one exists) or use a spacer, and get a pinion seal with less offset. Anyone got any good ideas or ever have this happen to you?

These are just a couple of pics I found on the web but they should help with my explination. The red areas are the parts I'm talking about. The top of the splines on the pinion are level with the top of the splines on the yoke. The washer under the pinion nut is touching both of them and not allowing me to tighten the nut to set preload.

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Post by needforspeed66gt » Tue Mar 13, 2007 1:49 am

Have you verified that you have the correct parts for the application? Measured against known 12 bolt parts and all dimensions are the same? The bearings and crush sleeve are the right thickness? If everything is correct, you could just chuck up the yoke in the lathe and face down the center to the depth you need, or make a shim like you were saying as long as you have enough thread depth for the nut.

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Post by Ed-vancedEngines » Tue Mar 13, 2007 4:41 am

A crush sleeve is usually very hard to get enough torque on for it to crush for the preload. Your actual preload is set by torquing against the crush sleeve as it is is drawn down into it's self.

Hope that made some kind of sense to you.

Once the sleeve is crused enough by torquing the nut on the pinion the yoke should alsobe further inside the housing, which will also move the yoke into the seal for a sealing surface to seal compatability.

If someone has modified the yoke to make it shoter for any reason it is considered to be not usable and will never be able to crish the crush sleeve or to go inside the seal.

Have you tried to fit it all in and to torque the pinion nut with yoke attached without the crush sleeve to see if it will tne allow the yoke to slide far enough to lemove all excess forward and rear play in the bearings?

I have seen instances where the bearing outer race needed to be shimmed away from the housing to give a greater distance between the front and the rear race. This is mosre of a problem with 8 3/4 Mopar rears though.

Now they make a solid crush sleeve replacemnt that does not crush, but I have never used one yet.

My suggestion is to try to assemble it all with no crush sleeve in place for initial setup.

Ed

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Post by Cammer » Tue Mar 13, 2007 11:37 am

Crush sleeves are being replaced with solid pinion bearing spacers. This is what they look like:

http://www.ratechmfg.com/gmsolidspacers.htm
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Post by JuicedBu » Tue Mar 13, 2007 12:05 pm

This is just going in a 70 Chevelle cruiser convertible so no need for using a solid spacer. The parts are right. I compared them to a set of stock gears. The pinion seal that was orriginally in there must have been something different because you can see where the seal was riding on the yoke and there is no way this new seal can. I took the seal and just slid it on the yoke and it sits about 1/4" from where the orriginal seal rode. If I can't get a different seal, I could always cut the outside of this one down and only install it half way into the housing and loctite it in or something. As far as the crush collar goes, I did orriginally set the rear end up without a crush collar and was able to get enough preload to check for my pattern and backlash. When I put the crush collar in, it's not even touching both bearings. If I had a longer yoke, or a spacer I think I could fix this problem.

Is there any problem I might run into putting a spacer in there?

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Post by Cammer » Tue Mar 13, 2007 4:57 pm

Make certain the pinion nut washer is in good shape and flat!

Make certain bearings are seated properly.

Do not like the idea of cobbling the seal.

Very hard to diagnose this problem from afar!
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Post by JuicedBu » Tue Mar 13, 2007 5:05 pm

The pinion nut washer is brand new. The top of the splines on the yoke and pinion are level with eachother. There should be a small space between the top of each. The bearings are seated fine. As for cobbing the seal, I wouldn't be changing anything with the sealing area itself, just the part where it's held into the housing.

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Post by lmsport » Wed Mar 14, 2007 7:56 pm

Lots of Danas use oil shields between the yoke and the front bearing. You could probably use a ford 9 preload shim as bearing is the same.

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Post by fast_crew » Fri Mar 16, 2007 7:21 pm

If you where able to get preload with the crush collar out then you should be able to get preload with it in. Something has changed since setting up with out the collar, and i don't think its the collar. If the pinion splines and yoke are flu sh now they shouldv'e been flush before while setting up. Maybe accidently switched yokes or bearing, hard to say.

Hope this helps.
Josh K.

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