Rear end decisions...

[laserjock]

Does anyone know the theory of the crush sleeve and how it works? It looks like to me if you overcrushed the sleeve, it would not damage anything since the deformation of the sleeve is taking the brunt of the force, and not really taking the bearing pre-load to the stratosphere like you would think. I am thinking that's why they started using it, for assembly line speed instead of paying some line worker to fiddle with shims all day. Just crank it down and go.

The crush sleeve is essentially an adjustable shim. You crush it down until you get the correct pinion bearing preload. That way on the assembly line you don't have a rack of precision shims to deal with the infinite combinations of tollerances and people taking it apart and putting it back together a bunch of times. Just like the lock washer, its an engineering abomination but it too serves its purpose.

 

[LCAM-01XA]

Does anyone know the theory of the crush sleeve and how it works? It looks like to me if you overcrushed the sleeve, it would not damage anything since the deformation of the sleeve is taking the brunt of the force, and not really taking the bearing pre-load to the stratosphere like you would think. I am thinking that's why they started using it, for assembly line speed instead of paying some line worker to fiddle with shims all day. Just crank it down and go.

When you first start putting it together the nut will spin real easy till all slack has been take out of the pinion shaft and the outer bearing and the crush sleeve are now firmly pressed against each other and sandwiched between the step in the pinion shaft and the nut. At this point the pinion will still flop around in the housing because the bearings are not preloaded yet. Then you keep applying increasing amounts of torque till nut starts turning again - this is the point where the crush sleeve begins crushing, thus slowly bringing the outer bearing closer to the inner one till the bearings make proper contact with the races pressed in the housing. Once that contact has been made any further tightening of the nut actually forces the bearings further into their races thus increasing their preload. It's important to note that proper bearing preload can be achieved even if you left the sleeve out and just let the outer bearing float on the pinion shaft, as it is the nut acting directly on the outer bearing (well, thru the yoke, but the yoke does not compress) that creates the preload - a prime example of this would be both front and rear wheel bearings, where there is nothing between the inner races and the outer bearing is floating on the spindle secured only by the nuts on the outside of it. The need for crush sleeve (or spacer and shims) is because on the outer side of the outer bearing we have the driveshaft yoke - the crush sleeve provides enough force against the back of the outer bearing that the yoke can be firmly tightened against the front of bearing. If there was no crush sleeve (or spacer and shims) any miniscule driveshaft vibration would cause the yoke to wobble, thus not only beating its splines but also uneven wear on the outer pinion bearing as a wobbling yoke will try to **** the bearing behind it as well.

If the crush sleeve was between the yoke and the outer bearing then your theory would be correct and the sleeve would act like a buffer for the excessive torque applied at the nut. However this would be no different from having no sleeve at all as far as yoke wobble is concerned. So sleeve gets placed between the bearings, thus providing a rear support for the outer bearing and the yoke. But again, with this design any excessive torque on the nut is transferred directly on the bearings, the extra-crushed sleeve is simply an indicator of how much further in the outer bearing has traveled along the pinion shaft due to the excessive force actin on it thru the nut.

Replacing the crush sleeve with a spacer and shims prevents you from overtightening the bearings too far because the spacer and shims do not compress like the crush sleeve does and thus there is only so much you can tighten the nut before you strip it and even if this is to happen as long as shim stack was good in thickness the bearings would have taken no damage at all. Effectively they both serve the same purpose of proving a rear support for the outer bearing against the yoke, only the crush sleeve is cheaper and faster to assemble (but you can easily overshoot and mess up the bearings plus supposedly cyclic loads during decel eventually crush it a bit more and result in loosening the yoke), while with the spacer and shims are more of a install-and-forget-forever deal (till the bearings wear out at least) however their install time is much longer and effort-consuming.

At least that's how I understand it. Someone correct me if you see anything wrong with all said above.

 

[LCAM-01XA]

I thought it was said before that the diff had to be out so i pulled everything apart, this whole time i have been working with just the pinion shaft in place. i looked over everything a few times, i dont remember any damage jumping out at me. but when i get back to this in a few days i will look it all over again. i am tempted to just buy new bearings regardless, becuase if i have to open this back up in the next 5 years i am going to light this truck on fire.

Well I just looked up pinion bearings and they are the same for both your 2nd gen and my 1st gen axle. Housings are the same as well. And bearings don't really compress. So my only guess as to why the collar ends up too tall is that maybe your 2nd gen pinion is machined in such a way that the step for the crush sleeve is a bit closer to the outer bearing than it is on my 1st gen pinion... Can you measure the distance between the face of said step and the face of the larger bearing? That bearing is always in the same position, so I think it can be used as a reference point. Then we can compare measurements and know if you need new bearings or shortening of the collar.

I'm determined to get to the bottom of this, you followed my advice to tear the thing apart so I cannot just leave you hanging and dealing with it on your own.

 

[metalminded]

After I cooled off a bit last night I had come to a similar conclusion, and iwas getting on hereto see if we could compare measurements.
Just to be clear, you are looking for the distance between the inner face of the inner bearing to the step in for the sleeve?
Just reading through , I have called the crush sleeve a washer, a collar and a sleeve, sorry for the inconsistency.

unfortunately, I am not home right now so I'll have to get back to you. I am thinking about ordering new bearings....

 

[LCAM-01XA]

Just to be clear, you are looking for the distance between the inner face of the inner bearing to the step in for the sleeve?

Correct! Also, don't worry about it right now, I won't be able to get to my pinion till the evening.

 

[metalminded]

Oh also... thanks so much for all your help. I hope I wasn't coming off like I held you in anyway responsible for my predicament, I 100% appreciate all the help I have gotten from everyone. Yesterday was a rough one, had my diff in my hands as the skys opened up and poured rain, it was a scramble.

 

[riotwarrior]

Oh also... thanks so much for all your help. I hope I wasn't coming off like I held you in anyway responsible for my predicament, I 100% appreciate all the help I have gotten from everyone. Yesterday was a rough one, had my diff in my hands as the skys opened up and poured rain, it was a scramble.

Both LCAM and myself suggested a correction, it sounds like LCAM is well versed in the CSEK and this diff, I however am not on this diff. Thus I'm keeping quiet. I'll be tearing one apart in a while doing CSEK too and I can deal with ***** when in hand and see what's going on. However I've got a hard time without seeing it myself.

Either way, we will git ya back up n running regardless.

My suggestion if you don't have a lathe and need to remove material from CSEK is to purchase a NEW whet stone a large one course one and sit for a while and hone it off rather than belt sander...just thinking it's more precise and flat. However yer choice and maybe someone else has an idea. I am not sure how much has to come off if any, lets wait for some measurements!

 

[metalminded]

A friend of mine has a lathe I can use if it comes to that which is nice. If the discrepancy isn't in the bearings, meaning the bearings check out to be ok in size, I may get new ones anyway as the longer I can prolong additional rear end service the better.

 

[franklin2]

but the yoke does not compress) that creates the preload - a prime example of this would be both front and rear wheel bearings, where there is nothing between the inner races and the outer bearing is floating on the spindle secured only by the nuts on the outside of it. The need for crush sleeve (or spacer and shims) is because on the outer side of the outer bearing we have the driveshaft yoke - the crush sleeve provides enough force against the back of the outer bearing that the yoke can be firmly tightened against the front of bearing.

The above makes sense. There is nothing to hold the nut from backing off except the locking function of the nut itself and the tension created by the sleeve. On the front wheel bearings you always have a cotter pin or a double nut system or some fancy locking mechanism to hold the nut in the proper position.

The only way I can see our simple method working is the crush sleeve has to relax or "spring back" a little bit when it loses it's tension(the nut works loose). I am also not sure how much torque difference there is on the nut from putting the pinion in a "froze up" mode being too tight, and a tightness that is acceptable, maybe causing a little heating from the tension being too tight. There must be some tolerance there, since I and lots of others do it all the time.

 

[LCAM-01XA]

Franklin2, idk for a fact if the sleeve springs back a littler when the nut works itself loose, but it does make sense.

Metal, I got around 70.4-70.5mm (so 2.772-2.776") on my 1st gen 4.10 pinion. It's a bit loose measurement, but I don't have a jig to hold the calipers perfectly square. What numbers did you get?

Riot, good call on the wet stone! Also I'm not well versed in this mess, I just had my axle apart like 3 times already, and there isn't much going on in there. Plus it's virtually identical to an 8.8 and those I can rebuild in my sleep by now

 

[metalminded]

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looks like there might be a 2mm gap on the bottom where the micrometer hits the bearing cage and not the flat face....

also, shouldn't the bearing be pressed on to the shaft? i turned the shaft upside down and the bearing slid down the shaft about 2-3 inches...

 

[LCAM-01XA]

To get a more accurate measurement there flip the calipers around, hook the end of the rail on the step and use the "stinger" to reach down and touch the bearing race face. Essentially how you measure the depth of a blind hole.

But wait, the large bearing just slid off? Ain't supposed to, it's a press fit there, need a shop press to remove it usually (or you can get surgical with a cutoff wheel). Also see the circular scores where the smaller bearing rides on the shaft? Those are an indicator that the pinion spun inside the bearing, and I bet the same thing happened to the large bearing as well. Probably happened when you ran the nut in with the impact at full throttle, the force created by it was so high that the bearings locked up and when you put truck in gear the driveshaft spun the pinion inside the bearings instead. Probably not a cause for major concern with the small bearing as it is a floater design from the factory and once clamped down between the CSEK and the yoke it ain't going nowhere. What concerns me is the large bearing, when the pinion spun inside it I hope it was the bearing race that got wasted, and not the pinion... Also is there a shim between the large bearing and the pinion head? There should be one, check carefully, it may have oil-glued itself to either the pinion head or the face of the bearing race, but it should be present there.

Anyways, get new bearings and see if the large one will go for a press fit next to the pinion head. And it's not a tap it into place tight fit either, it should require a shop press to get it into position. Post a pic of what the pinion shaft looks like with the larger bearing removed too, I wanna see if there are score marks there as well.

To get a more accurate measurement there flip the calipers around, hook the end of the rail on the step and use the "stinger" to reach down and touch the bearing race face. Essentially how you measure the depth of a blind hole.

 

[metalminded]

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the inner bearing slid right off the shaft.... f me....

 

[LCAM-01XA]

She's been spinning on the large bearing as well, both the shim and the pinion head show signs of it. The shaft however does not look too bad, yes it's polished but does not appear scored. Grab new bearings and see if the press fit is still possible.

 

[metalminded]

She's been spinning on the large bearing as well, both the shim and the pinion head show signs of it. The shaft however does not look too bad, yes it's polished but does not appear scored. Grab new bearings and see if the press fit is still possible.

seems like i need to get a new ring and pinion to me... the last thing i need is to get new bearings in there and have them spin! I really need this truck back on the road yesterday, how difficult would it be to swap in a new ring and pinion? I dont know what to do, maybe i will get new bearings and a new ring and pinion though i dont want to damage the new bearings on the old shaft...

any suggestions on where to get a ring and pinion? brand?