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Has anyone used a sleeve that is machined to the correct length to get the correct pinion bearing preload without using a crush sleeve? I have access to a lathe? Also the original gears had a .030 pinion shim, the new gears need a .015 shim to get the same pattern. I double checked to be sure the races were seated properly. Is this normal to have such a difference in shim thickness between gear sets? I don't know what the manufacturing tolerances for gears is.
68 Vetteman
Never done it but I don't see why you couldn't, getting it the exact right length may be a bit of a challenge. Another choice would be to make a spacer that you know is slightly too short and use shims to make up the difference, of course you'd need a selection of shims with the approximate correct ID and OD. If you do go this route make sure the pinion nut is TIGHT.
.015 isnt too much of a pinion shim change considering you're changing gears. In my experience, here is the progression of machining accuracy from most to least. 1. Bearings(if you change just the bearings all the old shim stacks should work). 2. Carrier(if you change just the carrier you MAY need to adjust side bearing shim stacks). 3. Gears(if you change just the gears you'll likely need to change the pinion shim stack). 4. Housing(if you change the housing you're almost guaranteed to need to change both the pinion and carrier shim stacks).
Rookie remark: The crush sleeve is probably one of those engineering ideas that saved GM $4.00 per car in labor costs.
Take pics of your precision spacer modification.....it would be interesting!
Hey Doorgunner,
I saw the list of projects on your 68. Hope you are making progress. I saw a picture of the 34 Ford. I have a 49 Chevy P/U (still in pcs.) sitting next to my 68. I didn't make the spacer yet. The old crush sleeve is .090 shorter than the new one. I'm thinking of using the old sleeve just to get me in the ball park and then machining the new sleeve to the correct length. This will be trial and error to get the right length. If I go short I can use a pc. of thick wall tubing to remake. If this fails I can use a new sleeve and crush it. I never did this so I don't know what to expect.
68 Vetteman
It's looking like the crush sleeve is half of the equation?
Pinion Bearing Preload - Is the amount of rolling resistance on the pinion bearings. This is adjusted by adding or
subtracting shims located between pinion bearings (more shim = less preload) Alternatively set by tightening pinion nut
with a crush sleeve in place, collapsing it until desired preload is achieved.
Pinion Bearing Preload is verified by rotating the pinion with an inch lb torque wrench. It is important preload is within
spec. Pinion bearings will fail quickly if over preloaded.
I rebuilt my 68 differential with the solid sleeve, for three reasons. 1) I thought it was easier to positively set the preload on the pinion bearings and then be able to take it back apart if I wanted too; 2) if you use the solid spacer, you will be able to change the pinion seal down the road in the car and get the same preload back by just torquing the nut to specifications and 3) I didn't find the process of crushing the factory style spacer very appealing.
I just used the kit available from Tom's Differentials, but if I recall correctly I did have to shave the spacer itself in a lathe since the shims didn't quite get the right preload.
I rebuilt my 68 differential with the solid sleeve, for three reasons. 1) I thought it was easier to positively set the preload on the pinion bearings and then be able to take it back apart if I wanted too; 2) if you use the solid spacer, you will be able to change the pinion seal down the road in the car and get the same preload back by just torquing the nut to specifications and 3) I didn't find the process of crushing the factory style spacer very appealing.
I just used the kit available from Tom's Differentials, but if I recall correctly I did have to shave the spacer itself in a lathe since the shims didn't quite get the right preload.
I have the same feeling about reason #3. I heard it takes a LOT of torque with the factory crush sleeve. A sleeve with adjusting shims sounds good. Thanks Doorgunner for the chart with the preload specks and torque numbers.
68Vetteman
I sneaked upon the preload torque on the pinion nut.....it took me three tries with my 1/2" drive torque wrench to get the correct preload pounds....seems I had both feet against the inner frame rail to pull hard enough on the nut........I used my 1/4" drive torque wrench to rotate/check the bearing preload between tightenings to get 10lbs. on the small torque wrench.
I sneaked upon the preload torque on the pinion nut.....it took me three tries with my 1/2" drive torque wrench to get the correct preload pounds....seems I had both feet against the inner frame rail to pull hard enough on the nut........I used my 1/4" drive torque wrench to rotate/check the bearing preload between tightenings to get 10lbs. on the small torque wrench.
I'm thinking 100-125 ft lbs with Locktite (High strength thread locker) on the pinion nut with 14-19 inch lbs of preload.
68Vetteman
I just used the kit available from Tom's Differentials, but if I recall correctly I did have to shave the spacer itself in a lathe since the shims didn't quite get the right preload.
Interesting Toms sells this piece since they once told me a crush sleeve was unnecessary, after having all my rear ends rebuilt by someone Tom personally taught who intentionally left out all the crush sleeves I got a bit concerned when a very well known Chicago area diff expert told me I needed either a crush sleeve or a machined spacer, when I called Toms and asked what they put in there (thinking it was a solid spacer) the guys said "air man air", obviously I had all me stuff redone with crush sleeves.
Interesting Toms sells this piece since they once told me a crush sleeve was unnecessary, after having all my rear ends rebuilt by someone Tom personally taught who intentionally left out all the crush sleeves I got a bit concerned when a very well known Chicago area diff expert told me I needed either a crush sleeve or a machined spacer, when I called Toms and asked what they put in there (thinking it was a solid spacer) the guys said "air man air", obviously I had all me stuff redone with crush sleeves.
"Air man air" pretty much sums up my conversations with Tom... He was very helpful to me actually.
We talked more about locating a good set of gears since at that time the good manufacturer out there had temporarily stopped making them and he didn't have any. The solid spacer was just run off in a list of stuff I ordered over the phone so there wasn't any conversation about the spacer use- I just ordered it.
Here are some pictures of the sleeve I machined to replace the crush sleeve. When the flange and pinion seal is removed this sleeve slides past the bearing race without disturbing the pinion gear.
68Vetteman
Very slick! So sounds like the plan is to shave it down till you get the right turning torque with the nut tight. Is that right?
That's what I did. I used the old crush sleeve and assembled the pinion gear. I had a little play so I machined my sleeve to that length. Next, back together with my sleeve and used a dial indicator to determine end play. Cut the sleeve by that amount and it gave me zero end play. Very close at that point and had 5 inch lbs of preload. I took .001 off the length and it went to 12 inch lbs of preload. That's good for me! I would not recommend this to other people to do unless you have a metal lathe and a lot of time and patience.
68Vetteman
That's what I did. I used the old crush sleeve and assembled the pinion gear. I had a little play so I machined my sleeve to that length. Next, back together with my sleeve and used a dial indicator to determine end play. Cut the sleeve by that amount and it gave me zero end play. Very close at that point and had 5 inch lbs of preload. I took .001 off the length and it went to 12 inch lbs of preload. That's good for me! I would not recommend this to other people to do unless you have a metal lathe and a lot of time and patience.
68Vetteman
Ahaaaaaaa! That's a good reference for anyone doing this mod......
02-08-2016, 11:01 PM
68 Differential Crush Sleeve
He was very helpful to me actually.
