Working on redoing the diff and go through refurbi'ng the Output shaft with new seals etc. Fit it in and buttoned it up, lock wire etc and test fit the brake caliper with original Shims in place (I was scrupulous about keeping everything and labeling sides etc) so I didn't mess up the shims. Anyway I mocked up the brake disk and caliper and it won't fit. It is too far outboard and the brake disk hits the outboard side of the inside of the caliper. I hypothesize that I did not tighten the output shaft bolt enough (causing the shaft to not come up the bearings enough) and that it needs another full rotation or maybe a little more or so. I'd say it is off (with original shims) about 1/8" maybe 1/4". Does anyone agree with this? Does this make sense? When I tightened the output shaft bolt, I tightened till I got no end play at all by feel (which is how Grant Francis said to do it). I don't have a torque screwdriver and while I have an inch pound torque wrench, it won't register at those low inch pounds.

If folks agree with my summation, what's the issue, if any, with just undoing the bolt a bit more and tightening enough. That crush sleeve could not be crushed enough if I am right?

 

If I'm following correctly, your brake disc won't fit satisfactorily into the caliper with it bolted in place.
When assembling the output shaft/carrier, there is only a few thousands between bearings that are a little loose and too tight, without a lb/in torque wrench I would agree with Grants advise. Gaining another 1/8 to 1/4" of shaft location is not possible.

Setting the shaft end-float with machined spacers, as outlined in shop manual, is on the order of a couple thou between loose and just right. I know you were scrupulous in keeping track of the various shims and where they came from, but here is the process (also in the shop manual).

Since the rotor and caliper are both fixed or bolted solidly in place, they have to be "fit" to each other, and that is done with the shims on either side of the rotor. There are two methods to do this: shim behind the caliper flange to move it out/in or move shims from one side of the rotor to the other, which moves the rotor in or out. The second method is much preferred. The goal is to get the rotor centered in the caliper opening, within a few thou, .010 I think. Again, because the rotor or caliper can't move side to side and find it's own center, like more modern cars, they have to be fit mechanically with shims when assembling. Example: if the rotor sits too far out-board of the center of the caliper, move shims between the in-board side of the rotor to the out-board side of the rotor. Opposite if the rotor sits too far in-board of the center of the caliper. These are the same shims that are used to set the rear camber also, but if you move them from one side of the rotor to the other the total distance between output shaft flange and drive shaft flange won't change. When you have the rotor centered, only the out-board rotor shims will need to be adjusted when setting camber.

If you are off-center 1/8 to 1/4", that's a lot. I don't think I had that many shims total at the rotors. A differential, especially an IRS, is one of the more inscrutable parts of the car. It's like being in the wilderness in the middle of the night, you're pretty sure nothing will eat you, but you really feel great when the sun comes up.

Dave

 

Thanks Dave. What you are saying is why I am thinking I haven't pulled the input shaft adequately into the shaft housing. Even with Zero shims behind the rotor, the rotor barely fits in in the caliper. Meaning that the only thing that can be affecting how far out the flange is proud of the housing , is the depth it goes into the diff. If I didn't draw it in enough, and I only THINK I tightened it enough, then I could be off a fair bit.

 

Something does sound out of place, take a look at this picture and see if the relative position of the output shaft to the carrier housing look like yours. The heads of the output flange bolts are only about 3/16" from the carrier housing bolt heads. Did the E-brake fit over the rotor without issue? If the output shaft is in fact not positioned correctly, you would have had problems with it too. You may have to take the shaft carriers back out of the diff and make sure something didn't hang up as you were snugging the bearing nut. If you didn't have to use a cheater extension with your socket when tightening the last turn of the nut, then you didn't "crush" the sleeve between the bearings. But there should be lots of slack in the bearings if this was the case.

P.S. Make sure the rotors are oriented the right way.

Dave

 

"The heads of the output flange bolts are only about 3/16" from the carrier housing bolt heads."

Thanks again Dave.

I think that 3/16" measurement and the setup shown in your first picture is where I have gone wrong. Your picture is taken on a slight angle and it is hard to see the spatial differences between the back of the rotor bolts and the tops of the output shaft housing bolts. I actually think these are supposed to overlap somewhat. It is hard to see. When I reassembled the output shaft parts I assumed that when torquing down the bolt I would pull that rotor flange in to the right place, but I don't think I did. I'm going to look at it now and see if I can make some sense of it.

Edit: I just looked and measured. For posterity's sake, they definitely do not overlap. and I measured mine and the distance is not 3/16" it is more like 4-5/16. So that would be my 1/8" that I'm off. Going to go make more observations and continue to edit.

Next Edit: So I looked at this some more and I was up a couple hours last night thinking about my hypothesis. I think this is exactly what has happened. I supposed that if I hit the center of the shaft rotor's flange with a hammer and was able to induce play where I didn't think there was any then it would confirm my supposition. So I did (if I was wrong I was going to have to take it apart anyway) and it did induce play. I moved it inwards about an 1/8 inch. Now it measures right close to 3/16 and still has some play. The caliper now just fits with a tiny bit of scratchy noise some of which may be related to it not being all properly torqued since I am just mocking it up. But I'm thinking I'll get another 1/16" or so when tightening the bolt. I think the 3/16" measure is really probably 1/8" in my setup as shimmed.

 

I follow, my 3/16" was from rough remembrance and may be slightly more/less. If you are in the "mocking-up" stage, did you actually tighten the output shaft bearing nut only until it came up against the crush sleeve and no farther? If you did, that's the problem. You will have to complete the process of tightening the bearing nut enough to bring the two shaft bearings in contact with their races which will take out all the play. To do this, you will have to tighten the nut past initial contact with the crush sleeve and very carefully "sneak up" on the zero play point. Crushing the sleeve will take the long breaker bar/socket I was talking about earlier, the sleeve doesn't like to be squeezed to the point of failure, but that's exactly its purpose. Setting the zero play/preload point on the bearings is where the lb/in torque wrench is used, the output shaft should not just spin freely like a wheel bearing. The nut should be tightened in very small increments until a slight resistance is felt when you turn the shaft by hand (if you don't have a lb/in torque wrench and discounting the drag of the seal). Remember, if you tighten a little (or a lot) too much, you can't just loosen the nut a little, never loosen and reuse a crush sleeve. You will have to start the process again with a new crush sleeve. You can make a simple, acceptable torque wrench pretty easily. We're working with lb/in here, not lb/ft, so a weight of 1lb at a distance of 1 foot from center of nut gives you 12lb/in (or 1 lb/ft). 1oz at 1foot gives you 1lb/in. I think I set my hub shaft bearings at 10lb/in (1oz at 10in). The torque values are in the shop manual, I believe.

Dave