taguy16

I finally got my crush sleeve eliminator issue figured out, so the next problem is when I put my "new" Torsen differential into my old housing with the original shims from the original housing in the original position to see how they fit it was a VERY tight fit. I had to drive in one of the shims. I re-pressed my bearings down to make sure they were all the way bottomed out and still got the same tight fit. Also, I have no backlash at all. I measured the shims from the 4th gen housing I got the differential out of and they were slightly thinner. I'm wondering if the Torsen diff. is a little wider than the original one that was in the housing. Obviously I need to so some work shuffling shims around until I get some backlash. The question I have is how do you determine how many shims to pack in the carrier bearings to get the right preload on these bearings since I obviously can't go by what was in there before? I know if you have too much preload on these bearings it can ruin them, but too little can't be good either.

Thank you for any help with this question.

TTOP350

iTrader: (8)

It's almost an acquired "feel" to get them snug.
there is a case spreader to help with the job, but I've never used one.
a carrier shim kit is a must when setting back lash and carrier bearing preload. A dial indicator with magnetic base or one that can thread into a cover bolt hole is how i setup for backlash.
im sure there's a few videos showing how to set it all up on the interwebz

taguy16

I can't find anything on setting the carrier bearing preload on a GM rear end. All I can find is one post on the Imud forum which describes the Toyota method of doing it by checking it at the spindle nut like you do the pinion bearing preload. The Toyota carrier bearing preload is 20 inch lbs. higher than the pinion bearing preload, which is only 10-12 inch lbs. I wonder what this would be for the GM 7 5/8 axle. My manual says to set the PINION bearing preload at 24-32 in lbs. for new bearings: I assumed that meant by itself and not with the carrier installed.

I have a factory shop manual and it doesn't mention anything about carrier bearing preload, and it doesn't go into much detail about anything else rear end related. The whole section on rear axles is probably less than 10 pages long. Seems like half the book is devoted to the stupid computers on these cars, however.

RJ IROC

If you google "carrier bearing preload gm" there are a gazillion posts, threads, videos about how to measure this. There isn't anything special about the 7.5/7.625 10 bolts other than the specs. You can even find info here and especially the fourth gen forums. Also, just think about it for a second....

How is carrier bearing preload different than pinion bearing preload? It is the same concept except now you have a gear ratio to worry about. Once you have your carrier installed and caps torqued, spin the pinion (with known preload) over with a torque wrench. You will get some number above what your initial pinion preload is, and that additional amount can be used to calculate carrier preload. If your new preload is 5 inch pounds higher and you have a gear ratio of 3.23, your carrier bearing preload is 3.23*5 = approx. 16 inch pounds carrier bearing preload. It really is that simple. In my experience it is almost impossible to get too much carrier preload with new bearings. It should be slightly difficult to get the shims in, as that is how preloading works (unless you are using a case spreader). The interference fit is what generates this.

I don't know if you are using used or new carrier bearings, as the preload is different in those cases. Used bearings need SOME preload, maybe 1/2 or less than that of new bearings. Just figure out what you need the additional preload to be and add shims until you get there. It is usually an iterative process to get the carrier bearing preload where it needs to be and backlash correct. You will know the total shim thickness needed for the carrier preload, but you may have to shuffle left and right shim packs around to get the backlash where you want it. I just did a carrier swap and went through this process with a solid pinion spacer a few months ago and so far so good.

taguy16

The general consensus seems to be that it is a "feel" thing. Or, with new bearings the carrier should be installed so tight that you can't get it out without prying it out with a prybar, but not so tight that you shave off metal with you are driving in your shims.

sofakingdom

iTrader: (1)

I'd be interested in knowing what the crush sleeve deal turned out to be. As wel as, how many of the shims ended up in there, and what the preload was before putting in the seal.

Personally I like to set mine at the high end of the spec range; usually somewhere around 25 in-lbs. Although, using the CSE, it's only adjustable in increments; I'd rather have it be just above the spec, than nowhere near the top of the range.

For carrier preload, it's REAL TOUGH to do it by "torque", for a variety of reasons. Usually I just do it by .001"s. That is, stack up shims until (a) I have the backlash I want which is usually toward the high side of the spec, like maybe .010 - .012", and (b) there's no play in it, and (c) I can just barely still get the carrier in with the shims already in there. Shims should stacked up with a .100" one on each side of each pack and thin ones in between those (bearing and housing are in contact with thick ones, thin ones are protected). Then take it apart and just add .005" to each side and put it back together. If it's not too hard to do that, I'll take it apart again and add some more, like .003" or something; and keep doing it until it's almost impossible to assemble. To get it together I set the shims in the housing and put the races on the bearings, then use 2 yyyyuuuuuuujjjjje C-clamps on the whole deal, to compress the races onto the bearings. I used to try to do it by "putting the shims in"; I'd be ashamed to admit how many of them I DESTROYED before I figured out to do it this way.

I don't think it's possible to ever get "too much" preload on it this way.

A "case spreader" looks like a square frame with 2 turnbuckles in it, that you bolt to the cover bolt holes and press the case open. I don't have one. Never seen one in person.

Reason for setting the backlash high is, things GROW when they get hot; meaning, the backlash GOES AWAY as the rear heats up. Now I don't know about you, butt a tiny bit more backlash when cold which you'll NEVER notice, is AHELLUVALOT LESS of a problem than 2 moving parts "growing" to a point where they try to occupy the same volume. Every time I've had parts try to do that, regardless of the parts involved, I've ended up with metal shavings. Not the way I want a rear end I've built to perform. Since we're all in the business of MORE POWER, which means MORE HEAT as a consequence, there needs to be MORE BACKLASH as well.

sofakingdom

iTrader: (1)

What was the CSE problem & resolution? How many of the shims did you end up using, and which ones? Seems like I usually end up with one of the thicker ones and 2 of the thinner ones.

taguy16

On the CSE I ended up having to use all of the shims that came with the Ratech kit to get the 24-32 in. lbs. of pinion bearing preload (for new bearings) my factory service manual recommended at 125 ft. lbs. of torque Ratech wants on the pinion nut. Since then I backed the nut off a tad after noticing several places like https://www.sierragear.com/setup-torque-specs/ are now recommending 12-15 in. lbs of preload (for new bearings). Also, with the 24-32 in. lbs. the pinion yoke had quite a bit of turning resistance: way more than I remembered it was when I took it apart. I always hate it when different resources have different specs for the same thing.

sofakingdom

iTrader: (1)

The torque on the pinion nut is largely irrelevant to the finished product... after all, that's The Point of the CSE in the first place. Once the nut is "tight", it's all metal-to-metal; nothing compresses, nothing bends, nothing changes, except that the tighter the nut is (to a point), the less likely it is to fall back off later. My guess would be that "a point" would probably be at least 300 ft-lbs or so, i.e. enough to strip the nut threads or the like. The bearing preload wouldn't change by tightening the nut from 125 to 300 ft-lbs though since nothing would change dimensionally. It's not really something that needs a "spec", like a head bolt or something, or a bolt that parts of its function is to stretch like a rod bolt; it needs to be "tight enough", but not "too tight". I'd describe the spec as 125 ft-lbs MINIMUM, with more being better. With a crush sleeve you usually have to stop tightening at 125 ft-lbs or thereabouts anyway; but since you're not using one of those, the factory "spec" no longer applies, and you can tighten it as tight as you want.

Yes 24-32 in-lbs is a fair bit of turning torque on the pinion... 2 - 2½ ft-lbs. You can usually get about 4 ft-lbs or so on a screwdriver before you hand starts to slip. Of course the yoke is bigger than a screwdriver handle, and a somewhat "better" shape for gripping as well, so your hand won't slip as easy; and the amount of force out at the radius is less than it would be with a (smaller) screwdriver handle; still, that kinda gives a perspective on the "feel" to expect.

What did you do to get the preload torque down to 24-32 in-lbs, when before, it was nearly impossible to turn? That would require either making the pinion longer, or the housing (distance between the bearing races) shorter. One way or another something would have had to change size or distance somehow.