Loose Pinion Questions

The outer pinion bearing on my Chrysler 8.25" burned up so i pulled it all apart and replaced both pinion bearings as well as the carrier bearings and all races. Also got new crush sleeves and a pinion seal. I set it up the first time and the pattern was a little off but i went ahead and ran it anyway. Sure enough, it made a little noise mainly on the coast side. So I pulled it apart again and changed the shims under the inner pinion bearing and got a more acceptable pattern. Well it still makes a very slight, almost not even noticeable noise so I'm going to do it all again. But what is weird is the first time i pulled it apart the pinion was loose. I just checked it today and it's loose again! I got the 12-15 in.lbs. rolling torque and used threadlocker on the pinion nut. How does the pinion keep coming loose?! After driving a bit could the crush sleeve be collapsing more? I marked the nut and it doesn't seem to have backed off any. I'm at a loss. Has this happened to anyone before?

Did you check your backlash before taking it apart the first time?

Your inner pinion bearing might not be fully seated against the head of the pinion. A bearing cup that is not square in it's bore can also cause this as well as rapid wear of the bearings. I usually use a threaded rod with a couple of nuts and bearing installation disks to apply alot of pressure on the bearing cups to ensure they are well seated in their bores. Look for uneven wear in the bearing cups, this indicates the bearing is not resting squarely in the cup.

I'm getting a little lost here.



There are no shims under the inner pinion bearing on the 8.25 axle. Pinion depth is controlled by shims under the outer pinion bearing (right under the pinion head).



Beyond that .... I am wondering if you properly "crushed" the crush sleeve. You can sometimes register bearing preload and still have slop in the pinion yoke. Best analogy I can give you would be that the sleeve is stiffest right before it starts to bend and is pushing back against the bearings trying to squeeze it down. Wouldn't think it would register 15 inch lbs -- but stranger things have happened.


Have never heard of a crush sleeve collapsing more after driving. And I really would not re-use the crush sleeve at this point. They're cheap enough to replace.



If all you did was change the bearings .... I would have left the same pinion shims you had in the axle from the start. And just worked your backlash better. By changing the pinion depth, you are engaging tooth contact in a different area that what has worn in.




Joe

You might also consider replacing the crush sleeve with a solid spacer kit.

I do have new crush sleeves and I used a new one each time. And yes, the shims are between the pinion head and the biggest pinion bearing, that is the inner. The outer is the smaller one closest to the yoke. I made sure to press the inner bearing fully on the pinion. I also made sure to check for any pinion slop before measuring the rolling torque. I fully seat the bearings then with the breaker bar I crush the sleeve very slowly and measure the torque each time until i get the desired reading. So maybe I'm really not crushing the sleeve all the way and it weakens shortly after install? It is all weird to me..

OMG .... what a brain fart this morning.



I cannot believe, looking back, that I had the inner/outter confused like that.




Looks like the medication I'm taking is stronger than I thought.



Scary, as I do this for a living. :anon:




I'm still suspecting that you aren't fully crushing it somehow. Whenever I do a "crush sleeve installation" I will torque it down a bit, then twist the yoke back and forth rapidly to seat the bearings and then re-check pinion preload. Sometimes that "tightness" you are feeling is just that the bearings haven't seated themselves in respect to the race. Especially after you are putting a torque force on them.



My gosh man ... I'm sorry I got that shim deal (with inner/outer) all botched up for you. :doh:

Haha no problem I space things like that all the time. But I think what you are saying may be the case. When I torque the pinion nut to crush the sleeve I do it very slowly and then stop and rotate it by hand. I get it to where it seems pretty tight when turning it by hand. To the point where it almost feels too tight. I have a couple more sleeves so I'll try tightening it and then tightening it some more. That is the only thing I can come up with as to why the pinion keeps coming loose.

DeftwillP said:

Did you check your backlash before taking it apart the first time?

Click to expand...

No, I didn't check it the first time I pulled it apart. I probably should have. But when I put everything back together I make sure I have the specified backlash. Mitchell OnDemand says 0.006"-0.008" and I read somewhere else that 0.006"-0.010" is acceptable. I get about 0.0075" and call it good. I wonder if it having 141,000 miles on it makes any difference??

The only other thing I can suggest ... is a new pinion nut.


Those stover-style nuts (with the crimped top) can only be used so many times. And even 271 Loctite can only go so far in terms of holding strength.



Joe

I also replaced the pinion nut. And instead of the washer that normally goes underneath it I used a lock washer. It was about the same thickness as the factory washer so I don't think that cased anything. Rather than tear everything apart again I figured I'd try and just tighten the nut today. I was as careful as I could be but I was pretty much blind since the carrier, axles, brakes, and wheels were still on. So I made my best guess and all of the noise went away so that confirms that it was caused by the loose pinion and not the way I set up the gears. Now the only thing that worries me is it seems to get hotter than it should. Will the new bearings and races cause a little more heat until they are broken in? This is the first differential I've worked on so I'm not really sure what to expect.:wierd:

It just feels hotter cause you never felt it before. Its called paranoia, and it affects all of us... They always get warm. Drive another car down the freeway for 10 miles, then feel the diff. Probably too hot to leave your hand on for more than 5 seconds.

I know they will generate some heat. Maybe I am paranoid haha. But yeah, I can't hold my hand on it for more than a few seconds. Just seems a little too hot..