thanks Jerry. that will no doubt be what I’ll have to do.
good idea-----I had planned to take one or two off and check. thanks
Four bolts through the two flanges with the disc solidly sandwiched in between. Single use non-nyloc lock nuts torqued at … see manual.
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thanks—also looks like the first flange is held onto the spline by a large nut (safety wired, I think) So–if that nut can loose, the whole thing would move, not simply the brake disc–right? and if so, I don’t get any other movement than the brake disc. sonder if the disc is warped a bit? A real mystery, and I can’t drop the IRS right now to check. 
On some diffs there is a nut there, but it should be stopped by a tabwasher.
I suspect that if the problem was loose output shafts (either a loose nut, or the fasteners holding the output flange carrier to the pumpkin itself then your diff would have been growling, groaning, and squealing, as well as clinking, clanking and clunking (Excuse the technical terminology).
I wouldn’t drive the car until I’d found the source of the problem and rectified it. It’s probably dangerous, and if you ignore it, it will almost certainly be expensive as well.
They are bolts so they will have a shank (possibly what you call a shoulder) but it should be short enough to allow full tightening.
If it is of any use - here is what the exposed threads looked like on mine:
And here they are with the axle removed:
UPDATE_______ Tonight I removed several of the nuts that hold the halfshaft and disc. It appears that the “shoulder” part of the bolt extends slightly past the opening which stops the tightening before full tightening happens----thus a loose disc. Tomorrow I will get new nuts and will add like washers on all for bolts so I can get the final tightening I need.
Several folks have said this is the way to go, so I will try it. If it draws the disc up tight, then I will hopefully declare success.
Any concerns about this approach?
I still have no idea what the clunk was/is.
Tom,
Me, I don’t see any problem with that approach, though I’d keep it in my head to replace the bolts when the opportunity arose (in 15 years or so), and check tightness often. Get grade 8 washers so they don’t yield and loosen over time.
Pretty simple fix, actually. You’ll likely have a new/different clunk! Programmers define progress as a DIFFERENT abort code…
Jerry
How many miles since you put in the rebuilt diff, Tom?
Jerry, if your disc and halfshaft flange have been moving around that much since install would you not expect to feel the slop in the camber?
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maybe 5000 miles-----------
I imagine you’d have noticed the problem earlier, Tom. If the disc/halfshaft flange suddenly came loose there’s something else at play besides bolt shoulders. Make sure.
Tom with a stock setup in good condition there is no way that the disc can be loose with the half shaft connected and the nuts tight. I’ve run with no shims to maximize negative camber and the half shaft / rotor lock up tight. Yes somebody could have replaced the bolts over 50 years, but it’s quite a job. You have to remove the hub to get the bolts out. These type of bolts are a press fit into the hubs often with serrated shanks to lock them in so they can’t turn in the hub when you are reefing on them to disconnect the 1/2 shaft.
I’ve got 4 diffs sitting on my garage floor and measured the dimensions. The bolt shank is .725 from the face of the hub to the start of the threads. With the disc attached it is .300 implying that the disc is .425 thick (I don’t have a disc off the car to measure). The 1/2 shaft flange that bolts to the disc is .315 thick, so the thread starts .015 below it’s surface, which is about what I would expect. They don’t want to take the torsional load of the disk or the 1/2 shaft flange on threads. Your idea to use washers to shim the nut is dangerous without first determining what is wrong. If the nuts are bottoming on the threads but not on the disc, you would also expect to see some movement in the flange as it would be loose too. If this was the case I would expect some noise from this. Also the 1/2 shaft flange has it’s on it’s face a circular flange that is a tight fit into the brake disc to ensue that it is centered. This alone should make the disk hard to wiggle - not to mention that the disc is usually held tightly by the brake pads. It could be wear in the hub bearings - then the whole hub. disk and 1/2 shaft would move as a unit. This much movement should cause the seal to leak a bit.
Sorry I can’t be of more help.
Don’t think it just happened Nick. It has no doubt been that way for a good while. In searching for the source of the other clunk I noticed it was very slightly loose------and very slightly, I have to emphasize. Why the shoulder of the bolts slightly extends past the hole opening is a mystery. It extends a very small amt,
We will know today if this solves the disc movement. I’m very excited to see.
thanks
tom
Thanks Terry. From what I can tell, nothing else has any movement except the brake disc, and its’ movement is very slight—but you can feel the movement. The shoulder of the bolt extension is almost non visible but there seems to be a small indication of the smooth part of the bolt that is visible-----and it is this small amt that is keeping the nut from fully tightening. I cannot feel any movement of the half shaft, and there is no noise from it. I
Hi Tom…can you post a photo…what discs do you have…could they possibly be thinner than usual…do you have any camber shimms fitted…have never tried it but maybe without any shims the nuts dont fully tighten… Steve…just re read a post above that says they do tighten without any shims
I just added grade 8 washers and new nuts-----absolutely no movement in the brake disc now. Taking her for a test drive in a few minutes.
thamks
tom
@tomfelts, Do you know anyone with a camber gauge? That would be a good place to go for the first test run.
unfortunately no. I’ll eventually go to my favorite mechanic who can ck it for me. I did a 15 mile run today and all was well.