gord327

New kid on the block...would appreciate some advice.

Set up my pinion preload last night and went a tad too far...about 10 INCH-pounds. Backed of a tad on pinion nut and it is now reading around 25 INCH-pounds.

Before any preload appeared, I could spin the yoke about 1/2 to 3/4 of a turn. After getting to 25 INCH-pounds the pinion is fairly stiff to turn but it can be turned by hand. Even the INCH-pound torque wrench turns it fairly easily although there is a very slight tug before it reads.

Does that sound right, as far as the yoke feeling fairly stiff to turn?

***************

I know about crush collars and over-tightening them but since I only exceeded by a few INCH-pounds I'm wondering if I can get away with this one.

sofakingdom

iTrader: (1)

Well, that's kinda the definition of how "preload" works... it's supposed to be x inch-pounds "stiff to turn".

I tend to set mine up toward the tight side of preload. If I had one at 35 inch-pounds I probably would have left it. But that's just me.

Way to measure it of course, is ONLY when already moving; NOT "breakaway". If you've got it to 25 now, and the crush sleeve isn't loose (that's what I'd be worried about, backing off the nut: I NEVER EVER EVER FOR ANY REASON do that, since if the crush sleeve doesn't expand back out and take up the clearance, the nut will be loose, and WILL back off during service) it will be OK. That's not a real safe bet IMO. Again, if it was me, I'd put a new crush sleeve in it and start over. All of which is why a lot of us recommend a solid spacer instead of a crush sleeve: NOT ONLY is it possible to take it apart and re-try, BUT ALSO, you can tighten the nut until it absolutely begs and pleads and even weeps and screams for mercy, without disturbing the preload setting, instead of having to stop tightening when the desired preload is reached.

gord327

Normally, I would be concerned as well. However, if the sleeve had crushed too far, I am reasoning it would not have rebounded enough to give me the 25 INCH-pounds I have now.

I assembled it previously with the old crush sleeve in there and there was no preload at all. I had done that because after assembling with the new crush sleeve I had about 1/16" end play in the pinion shaft. I could move the pinion shaft in and out about a 1/16th. That was about the difference in length between the old and new crush sleeves.

After torquing it for a bit, the end play diminished to no noticeable play and that's when I started watching the preload.

I was cranking the pinion nut about 1/8th turn between torque wrench readings and I must have tweaked it a bit far. I was likely right on the verge of a preload showing on my last torque.

I should have been more careful but I am reasoning that a crush sleeve is going to compress somewhat before it distorts enough so it wont spring back. In my case, it obviously sprung back a bit.

If I still have 25 INCH-pounds preload, I don't see what else could be doing it other than the crush sleeve pushing against the bearing. The pinion nut is pushing on the yoke and the inner surface of the yoke is pushing on the front bearing inner collar, which is pressed onto the pinion shaft. The other end of the bearing collar pushes against the crush sleeve. The other end of the crush sleeve pushes on a collar on the pinion shaft.

The crush collar acts like a spring and if I had backed it off too far I'd have no preload, just as I had with the old crush collar in there.

I don't know, I am just hypothesizing.

big gear head

It's not worth taking a chance on it. Put a new crush spacer in it and try again. I wouldn't go 25 inch pounds. I wouldn't go past 20 on the 7.5 rear end.

sofakingdom

iTrader: (1)

The crush sleeve has NOTHING WHATSOEVER to do with preload.

Let's compare this to, say, front wheel bearings with a cotter pin.

You can set those the same way: tighten em to some preload spec, then put the cotter pin in to hold the nut still. You can get em to however tight they need to be, and THEN SOME, with a 6" crescent wrench. (if it opens wide enough to go on the nut...) Eh??

The crush sleeve performs the same function. You could leave it COMPLETELY OUT, and tighten the pinion nut, up until the preload on the bearings gets to where you want it. Eh?? (In point of fact, some old rears back in the day when cars didn't go above 50 mph or so, still used cotter pins on the rear end. Classic trucks, up to about 59 or so, still did.)

So, in the end, what does the crush sleeve have to do with preload???

NOTHING.

All it does, is give the nut something to tighten against. Ideally, you keep tightening the nut, a tiny bit at a time; each time you tighten it one scosche, the crush sleeve crushes a tweeeeek, and the preload increases by about ... an ooooch. When the preload is reached, the crush sleeve is crushed however much, the nut has however much torque it took to crush it (the torque on the nut that produces the preload is TRIVIAL: if you left the sleeve out you could almost get yer 20 - 25 in-lbs BY HAND); all the sleeve does, is provide some resistance to the nut, to keep it from backing off.

So, if you tighten the nut to the point that it crushes the sleeve TOO much and then back it off, it's no longer tight against ANYTHING, and no matter what the bearing preload is, the nut is basically free to loosen or whatever else it feels like. (which most likely is, either it will loosen, or if it doesn't do that, it'll just get looser... given that it only has 3 things it can do: it'll either tighten itself {insert loud obnoxious game-show buzzer here}, it'll do nothing, or it'll loosen... whaddya think??)

Change the sleeve.

You've heard one vote for going to the tight side of the spec, and one for going to the loose side. Frankly I don't think it matters all that much: HOW you get there is more important than EXACTLY where you get to. If you do it RIGHT, there's probably less than 1/32 of a turn from the bottom of the spec to the top; tiny. Again, it's TRIVIAL. Once you're in the range, you're ... in the range.

Get a new crush sleeve in the morning, apply what you've learned, use more discretion as you tighten, life will be good.

gord327

Thanks for the info. Do the ehs mean you are Canadian? I'm from the 'Wet' Coast, near Vancouver.

I am not interested in getting into an argument about it and I am not calling you wrong. However in the Yukon Manual that comes with their bearing kits they say the following:

"The pinion bearing preload is related to the amount of force the pinion nut exerts on the pinion and its bearings.....Axles generally use crush sleeves or shims to set pinion preload".

I don't see how you can. The nut is tightened on the front axle to a specified torque then backed off to the nearest hole in the axle that will take a cotter pin. It's barely more than finger tight. At least, you can tighten the nut most of the way finger tight and it doesn't take much with a wrench to finish it.

I agree with you completely that the preload is not much more than the front axle bearing preload and that all the force is required to crush the crush collar. Once it's crushed, there isn't a lot of force between the pinion nut and the bearing.

However, the crush bearing serves another purpose. On the Timken site, there is a movie that shows the different types of bearings. Bearings like rear axle bearings are designed purely for vertical force, like the weight of the vehicle, and not designed for lateral, or sideways force.

The slanted bearings used on the pinion are designed to carry force both vertically and sideways (along the shaft). The outer race that holds the roller bearings is designed to flex sideways with respect to the inner sleeve that is pressed onto the pinion shaft. That's where preload comes in according to Timken.

When you set preload, you are actually putting pressure on one part of the bearing sideways with respect to the inner part of the bearing. When the slant bearings press on the races that are inserted into the diff housing, and the pinion nut is tightened, the preload is the amount of force applied to the holder with the roller bearings as opposed to the inner collar.

Please note that the rear bearing inner collar, next to the pinion gear, is pressed onto the pinion shaft very tightly. It's not going to move. However, the front bearing inner collar (on the bench) can be pushed onto the pinion shaft by hand right up to the crush collar. If the crush collar is removed the front bearing can be pushed even further.

Without the crush collar the front bearing would keep sliding along the pinion shaft, and as the outer race with the roller bearings came in contact with the race pressed into the rear of the diff housing, it would put far too much sideways strain on the bearing.

You need resistance against the inner (pressed) front bearing collar to push back on the yoke inner collar as the nut presses on the yoke outer surface. The inner end of the crush collar is held by a collar on the pinion shaft. Otherwise, you need a solid collar with shims to set the exact distance the front bearing inner collar should slide onto the shaft.

With the crush bearing in place, the front bearing inner collar is stopped by the crush collar at a prescribed distance. When you tighten the pinion nut, it presses the front bearing against the crush collar via the yoke. Tightening the nut till the crush collar compresses, and testing the preload on the nut, tells you how much you have pushed in the inner collars wrt to the outer roller bearing races.

If you remove the crush collar and start turning the nut, there is nothing to pull on the rear bearing. The front bearing will keep pulling into the space where the crush collar was located and it will likely destroy the front bearing by pushing it well beyond its sideways tolerance as the outer race of the front bearing contacts the race pressed into the diff housing.

gord327

Thanks for feedback.

I'm waiting to get info back from Yukon Bearing. I have done a gear marking using the GM yellow compound and the markings don't jibe with anything in the Yukon manual.

In the manual, they claim with a used pinion/ ring gear assembly to ignore the drive side of the gears and use the coast side for the marks. In that case, I might be OK, since the marks are generally within bounds.

I am under a time constraint. I only have a week to get this job finished and I don't feel like taking a chance by stripping everything down again to redo the pinion shaft, if it's not necessary.

When I was torquing the nut, my 24" breaker bar was flexing in a scary way. All I need is retorquing and busting it.

sofakingdom

iTrader: (1)

You haven't figured it out yet.

Pinion bearings are EXACTLY IDENTICAL IN EVERY WAY to front wheel bearings. In fact, some of em are even the same part #s. They work EXACTLY THE SAME WAY.

To get wheel bearings to the correct tightness, you tighten the nut. (duh) You stop tightening it when the desired preload on the wheel bearings is reached. You might measure that by turning the rotor, or you might measure it by torque on the nut; doesn't too much matter; when the bearings reach the correct pressure along their axis, they are properly tightened. At that point, to hold the nut still, you put a cotter pin in it.

Rear axles used to work EXACTLY THE SAME WAY. In vehicles as recent as late 50s Chevy trucks, the pinion nut used a cotter pin. The reason they don't do that any more is that the speed of everything rotating is too great nowadays, and the force required to hold the nut still just against mere rotational inertia is great enough that over time, it'll shear a cotter pin.

So now we use the "crush sleeve" system. As you tighten the nut, in addition to it pressing the bearings together (which consumes only a TINY BIT of the overall torque you're exerting), it also crushes the sleeve (which consumes VIRTUALLY ALL of the torque you're applying); it's designed to require a great deal of force to crush the sleeve, such that the nut requires a great deal of torque to turn, either to tighten further (as you've discovered), or to back off. But as far as what happens to the bearings, it's COMPLETELY irrelevant. You can just as easily tighten the nut to the point that the bearing preload spec is met with the sleeve COMPLETELY ABSENT. (just like wheel bearings) Of course, you couldn't possibly leave it like that, since the nut could then just back off all on its own as easy it is for you to tighten it to that point without the sleeve to tighten it against. One way or another, there has to be a way to keep the nut from turning.

Not sure what you mean about the "front bearing keep sliding"... where do you think it's going to go? Once the pinion is inside the housing, the races establish the minimum distance along the pinion that the bearings can be from each other (set by the distance between the races); just like wheel bearings, there's no way for the bearing to keep sliding down the pinion. That's PRECISELY what "preload" is all about: pressing the bearings together until all the play along the shaft is taken up (which requires virtually no torque on the nut at all), then just a little bit more to where there's "negative play" so to speak, which requires only a very slight torque on the nut.

Once you figure that out, it'll become obvious to you that the sleeve itself has NO RELATION AT ALL to the preload, and is solely the retention method for holding the nut still once the desired preload has been applied.

You're right that without the sleeve, it would be VERY easy to destroy the bearings by over-torqueing the nut. For that matter, it's not all that hard to do the same thing WITH the sleeve in place. If you had tools that weren't so wimpy, you'd see just how easy it is. You've already managed to over-torque it a little bit with what you've got; there's nothing whatsoever stopping you from over-torqueing it ALOT except the weakness of your tools.

Tapered roller bearings ALL work that way. Wheel bearings, pinion bearings, the ones in any other kind of machinery, ALL OF EM. There's any number of schemes for holding the nut still once they're tightened to the point that the proper preload on them is reached; the "crush sleeve" is just one of many such methods. And as I said earlier, it's FAR FROM "the best", even in the application at hand; it's just real convenient for a mass production situation, and even if not "The Best" and CERTAINLY not "The Easiest" for someone outside a factory, totally adequate for the application. A solid sleeve with selectable shims is MUCH easier for somebody like us to assemble.

Since you've already ruined your existing sleeve by over-torqueing it and now the nut won't be as tight against it as it's supposed to be, you need to pull it out, replace it, and start over. Otherwise the nut is ALMOST CERTAIN to back off, and that sooner rather than later, because it's not tight up against the sleeve anymore. Won't matter that you get the preload right if the nut isn't held relatively permanently in place.

You'll probably need a new seal as well as the new sleeve (or better yet, a solid spacer w shims http://www.summitracing.com/parts/rat-4111). And a better breaker bar too.

big gear head

The Yukon kits come with 2 crush spacers. Do you have another one? If you do then use it. If you don't then get another one and use it. Don't cut corners on something this important. You may think you don't have time to do it right this time, so I'm guessing that you don't have time to take it all apart and do it over again when the pinion bearings fail. Pinion bearing preload is one of the most important things to get correct when building a rear end. A crush spacer doesn't spring back if you over tighten it and then loosen the nut.

gord327

It's not the time, it's getting the space to do it. I would gladly putter with this forever to get it right, but I have to be off this space in a week, otherwise I have to do it on the road. The neighbours wont like that and I wont like it if some goof smashed into me while I'm under my vehicle.

I have other problems at the moment. My backlash is a little tight and I need to move the carrier a tad to the left (toward ring gear side). There is a shim kit in the Yukon kit but two of the shims have collars on them. The shim part is 10 thou and the collar is 10 thou.

I don't know what the purpose of the collar is. The unit is precisely machined so I can't see it being a holder for the other shims. I am guessing that the collar part is to hold 10 thou worth of shims so you can pound them in without bending them.

About the crush collars, I hear what you are saying and I agree in principle. It's better to do it again and I do have the spare collar from the kit. However, metal will bounce back if it is not bent too far beyond its crush point.

I have worked with lots of metal over the years and I know that you have to bend some metal well beyond the position you want it because it springs back. I did not compress the crush collar more than 10 INCH-pounds beyond where it needs to be in order to be in spec.

If I have the time, I definitely will replace the crush collar. Right now I have to figure out the Yukon shim package and get the carrier moved over a few thou.

I read a ROT for that. If you shim the carrier 10 thou toward the ring gear side, it will free up 7 thou of backlash. I don't need nearly that amount and I am thinking of putting a 5 thou shim beside the stock right shim, which looks to be about 30 thou.

The one on the other side looks to be about the same (about 30 thou) so I need to reconfigure the shims on that side to be about 25 thou.

gord327

I'll get back to you but thanks for response. I need to get out and work on the beast and there's to much detail to address in your reply.

What do you know about carrier bearing shims with collars on them? The Yukon kit has two 10 thou shims with 10 thou collars on them. The shims are standard in every way except they have a 10 thou collar attached at the opening through which the axle passes to reach the splines in the carrier.

sofakingdom

iTrader: (1)

Don't try to set the carrier up, either its preload or the backlash, until you get the pinion DONE AND OVER WITH. (yes, the carrier bearings get preload too, same as any other tapered rollers)

Because, you'll just have to take the carrier back out again to doink with the pinion, and there's no sense in doing all that dirty 4-letter word that starts with a "w" twice. Once is bad enough; twice is a crime against dignity.

Can't speak to the matter of the collar, except that, I've seen housings where the place the shims sit up against, is destroyed from bearings spinning or whatever. Might be intended to replace that surface. Best thing I can suggest is, figure out what the collar will sit inside of or around.

When you get around to working on the pinion again, JUST TRY what I said: put it all together WITHOUT the crush sleeve in there, and experience for yourself all about bearing preload without at the same time crushing the sleeve. You'll find that it's a revelation and will instantly make clear what you are struggling with getting your mind wrapped around. Just be REAL CAREFUL not to over-tighten the nut and destroy the bearings, which you'll almost be able to do with your bare hands. Also make sure you lube the bearings with something before preloading them; just pouring some gear lube in them is fine. If you didn't already do that you might want to get another set of pinion bearings too before you button it up, sure as hell beats putting the whole thing all together and discovering the bearings already got brinneled and spalled from running dry with load on them and you just gotta take it out and start ALL OVER again.

gord327

Talked to Yukon. They said the collar is for making a shim sandwich. You put the thinner shims, that wont take force when inserting them, onto the collar and point the collar down the axle tube. The thinner shims sit between the 10 thou shim attached to the collar and the end housing where the shims normally sit. If you have to, you can force a thicker shim between the 10 thou shim and the carrier bearing race.

Already done that. When I inserted the new crush collar and assembled the unit, the pinion shaft had far too much play in the shaft direction. Could not figure why so I pulled it apart and put the old collar on. The play was gone. That's when I figured out that you have to crush the collar a bit to take up end play before starting the serious torquing.

On the bench, without the crush collar in there, the front bearing slides well past where the crush collar would be. IMHO, the crush collar prevents the front bearing inner collar being torqued in beyond a certain point thus ruining the bearing.

With only the old crush collar in their, during disassembly, I measure no preload at all. With the new one in their during assembly, I had to crush the collar a fair amount before preload began to show. Unfortunately I went a tad too far and I'll know better next time.

I measured the old and new crush bearings lengthwise. The old was 0.057" and the new was 0.62". The difference is 0.05", which is a tad under 1/16" and that was about how much end play I had before crushing the new one.

I did lube the bearings.

I'll get back later, I am just taking a break.

Please don't take offense at me debating a point with you, no offense intended.

Like Schultz on Hogan's Heroes...I know nothing.

sofakingdom

iTrader: (1)

How is

the same as

???

Of course it does: BUT ONLY IF THE PINION IS NOT IN THE HOUSING.. Once the pinion is in the housing, THE BEARING RACES stop the bearings from sliding ANYWHERE past them. Just like wheel bearings. Absolutely identical the same in every way. Think, look, draw it on paper, read it on Wikipedia or HowStuffWorks, it's all the same.

The point you are steadfastly avoiding picking up on is, the crush sleeve is IN NO MANNER WAY SHAPE OR FORM related to either preload or end play. All it is, is the retention method for the nut. If you were to put the WHOLE THING together WITHOUT A CRUSH SLEEVE IN IT AT ALL (WHOLE THING: pinion, both bearings, in the housing with both races, and nut... just, no sleeve), you could still adjust the nut and get the preload you want, almost by tightening the nut with your fingers. EXACTLY like a wheel bearing. At that point, all you'd need, is a way to hold the nut still, and you'd be golden. For example you could do like some other tapered roller setups and add a jam nut on top of the main nut to hold it still; but that wouldn't be very permanent either, unless you put acoupla hundred ft-lbs of torque on the jammer, same as you put on the nut crushing the sleeve. You could almost certainly get enough preload in that sleeve-less state if you put the socket all by itself (no ratchet or anything) on the nut and just cranked it with your hand. Of course, if you did that and installed it in the car, it probably wouldn't make it backing all the way out your driveway before the nut loosened itself, because there wouldn't be anything retaining it; but as far as PRELOAD, the bearings wouldn't even notice the absence of the sleeve. The crush sleeve is not related in any way to generating the preload.

But that "retention" thing you're fighting back against, is PRECISELY WHY you need to put a new sleeve in it. If you do not, you will CERTAINLY find yourself in a few hundred miles with a rear that makes noise, has weird vibrations when coasting, clunks and grinds when backing up, and so forth, because the nut WILL back off. You only get one crush out of a sleeve, and then it's all over with. You need to change it out, else the nut will not be adequately retained, and failure will be the inevitable result.

Once you understand what each individual one of the parts is actually doing, and then because of what THEY do, what YOU are actually doing, it will all make a great deal more sense to you. Stop trying to fight back and defend yourself and tell me all about how I'm full of canal water and all that, and instead THINK and LOOK and LISTEN to REALITY, and you will actually LEARN something that you can use to your advantage.

Meanwhile, if you don't already have another sleeve, I strongly recommend getting the thing I linked you to acoupla posts above. It allows you to torque the nut MUCH tighter than with a crush sleeve, thus providing a FAR more secure retention for the nut than the sleeve does, without requiring you to torque the nut to determine the optimum spacing between the bearings, and with the added advantage of being re-useable. Much much easier for someone out here in real-world-land to execute than a crush sleeve, ESPECIALLY if you also get another tail bearing and hone it out with a brake cyl hone so that it slides freely onto and off of the pinion. Then once you find the right shim stack, you can put your un-honed bearing back on and torque the nut until the threads damn near strip, and it will NEVER back itself off.