1991Z28

I read in some of the tech articles and in some mags that using a solid spacer with shims instead of a crush sleeve (on the pinion) helps longevity and durability of the rear end. I was talking to a shop this morning that basically said they don't know what they're talking about...said you'ld be more likely to destroy the gears or housing before you crushed that sleeve further. I'm leaning towards the solid spacer, still, and not that shop, but I just wanted to hear some of you verify that this is the better option for me ...Anyone know where to get one for a 7.5" 10 bolt in a 1991 Z28? I looked in Jegs and they didn't have any listed for that size...Summit didn't even have any solid spacers in their catalog at all. TIA (By the way, I've already got a girdle for it.)

82camaro

Solid spacer is better, but I know of alot of fast GM cars that use a crush sleeve that never have any problems. Mine has been trouble free for 5+ years with a new crush sleeve--the one I took out was fine as well.

25THRSS

What are the disadvantages/advantages for each?

RB83L69

First, understand what those parts do.

There are 2 bearings that hold the pinion; both are tapered rollers. They are somewhat like front wheel bearings. You know how you tighten the nut, and as you tighten it, Whatever play it has, goes away, as you continue to tighten it, it mashes down on the bearings, and the wheel gets harder to turn. When you get it to the tightness you want, you put a cotter pin in it to hold it there.

The pinion bearings work similarly, except that since the nut spins, a cotter pin isn't really a good idea. Used to be used on older cars back up to the 50s, when they didn't go so fast, and people's expectations for a smooth ride weren't so strict. So now they use a crush sleeve; you tighten the nut, the sleeve crushes, eventually you get to a point where you've reached the correct bearing preload; the sleeve holds some tension on the nut, to keep it from backing off. You hope.

The solid spacer's shims are chosen the same way; you put the thing together with all the shims, measure the free play, take out that much shim, measure again, etc; you keep adjusting the shims down until you get the preload ("negative play" if you will) that you want. Then you tighten the nut until it screams for mercy.

The solid spacer allows you to tighten the nut down tight enough to where it won't back off, and the crush sleeve doesn't allow that. The nut can be tightened to hundreds of foot-lbs with the spacer; the crush sleeve will sometimes produce not much over 100 ft-lbs of torque on the nut before the bearings are preloaded to the desired amount. The spacer won't ever change, the crush sleeve will.

THe crush sleeve is easier to install. Put it in, tighten the nut until you get the bearing preload you want, you're done. Great for a slap-it-together production-line job; sucks for high performance.

Obviously you're dealing with a production-line shop, not a racing one. Go elsewhere. Don't buy your rear end work from the low bidder.

RB83L69

Oh I forgot....

http://www.drivetrainspecialists.com...=28&cat=GM+7.5

can't miss it

ede

never used a solid spacer, i ithnk i will with my next rear i do. one big problem i have with the 7.5 ten bolt is going past the preload setting and having to start over which means a new crush sleeve. i used a crush sleeve on a low 11sec (high 10 on a very good day) z/28 that lifted the front when it launched and the rear never failed, except for spider gears. finially went to a spool and fixed everything.

Tom 400 CFI

This is one area that I am not as familiar as I would like to be.

RB, thanks for the detailed explaination. But I have a couple questions. If the purpose of the crush ring/solid ring is to provide friction against the nut, so the nut won't come loose, why not assemble the thing w/no ring, adjust preload to desired amount, and peen the nut? Or just use Loc-Tite?

I assembled the 9 bolt that currently resides in my car about 11 years ago. Out of necessity and circumstance, I was using ALL used (junkyard) parts. I was moving, and my mission at the time was to get the thing assembled, get moved (using the car), and "fix" everything later. I was hoping the rear would last the driving distance of the move (~200 miles). Anyway, I re-used the old crush ring, tightened the nut to the (my) desired preload, and then beat the end of the nut with a hammer. It's been 11 years now, many passes down the track, and I've only had the cover off to change fluid. Can you comment on what was right/wrong with what I did? Why has that worked? etc? Thanks
-Tom

RB83L69

Loctite is totally inadequate, compared to the torque on the other parts. What does it take to break it.... 50 ft-lbs? 100 ft-lbs? That's a little of nothing compared to the torque that should already exist there. You might as well use Elmer's glue to hold it in place.

You could peen the nut; but it's already a lock nut. Again, not much improvement in holding strength there.

The reason what you have done has lasted for you is luck, pure and simple. Sometimes they work that way and sometimes they don't. Sometimes it works OK but you end up having to re-tighten the nut every however often, because the crush sleeve doesn't offer enough resistance to hold the nut still, and it backs off over time. Next time you try that it might only last a few hundred miles. I don't know how to predict which will happen.

The crush sleeve, or solid spacer, goes in between the bearings, so as you tighten the nut, it either crushes the sleeve (irreversible, but the process can continue, in which case the nut has only its lock feature to hold it still) or tightens against the spacer, as it pushes the bearings closer together and takes out the play. Using a spacer you can tighten the nut really really tight, to the torque that a 7/8" thread is capable of withstanding (should be somewhere in the 3-400 ft-lb range) instead of merely tightening it until the sleeve crushes far enough for the bearings to move close enough to get the preload.

Tom 400 CFI

Thanks for the well articulated, understandable answer, RB.

RB83L69

Any time

25THRSS

With my car now, I don't forsee me ever surpassing 400 hp. Do you think a crush sleave could handle that amount of power on drag radials?

Zac's92

the crush sleeve doesn't handle any power. the pinion pushes the ring gear which pushes the pinion back aginst the case, that increases the load on the larger pinion bearing and decreases the load on the smaller(closest to the yoke) bearing. the on and off application of power to the pinion causes the bearings to load and unload which can cause the nut to loosen. the biggest advantage I've seen in using solid bearing spacers is in 4wd applications where rocks hit the yoke on the rear axle crush the sleeve and the pinon bearings get very tight.


Zac

bohn333

i put in the solid spacer in my rear, i guess the only real benefit of them is that it stops the pinion from walking up the gear under high loads of torque. I figured it was just good insurance to have since i dumped almost $700 in the rear. Reider racing sells them for about $12 for the 7.5 rear. Thats were i got mine.

Zac's92

btw,

I work for a 4wd shop building axles everyday, and I think a solid spacer is better only because its easier to use. If its not right you change the shims, where as with a crush sleeve if you crush it too far you gotta use a new one.

There should be no torque on the nut the yoke is splined and so is the pinion. There may be pressure in line with the pinion but no rotational force on the nut. All the nut holds is the yoke aginst the bearing on the pinion. Most pinion nuts are lock nuts(as mentioned earlier), that and loc-tite is more that adequate in keeping the nut from vibrating loose. Factory toyota axles use a peened nut to lock it in place.

25THRSS

I understand that the crush sleeve doesn't actually handle any power. I meant would my rear be ok for about 400-425 flywheel hp max on slicks with a crush sleeve or would it be worth my while to put in a solid spacer? Why didn't gm do this from the factory? Are there any downsides to a solid spacer?

Zac's92

If you are rebuilding the axle already put one in. but it's not like you need to take your axle apart and put one in because you swapped to a engine with more power. the only down side (as mentioned before) is in production line assembly. the solid spacer takes a little longer to put together.


Zac