Working an a 742 Case 8-3/4" diff and need to add a 0.008" shim to the pinion, but the thinnest shim I have is 0.010"
Is there an easy way to sand the shim down slightly? I could try a 2" Rollock sanding disc, just not sure how uniform that will work?

Front bearing pinion shim or rear pinion bearing shim?
I may have several thin ones of each so you could make a .007 or .008, I think the old Mopar shim kit came with .003,.005, .010 and up from there, maybe not depending on what tool your using to measure with

,002" difference between what you have and what you need? That's really close. I would install the .010" shim, set backlash, and pattern sweep on drive and coast side before chasing down an .008" shim or a combo. Don't bother trying to thin the shim. Although, you could polish the back of the inner bearing on some emery, do the same to the bearing cup and install the .010" if you really need that .002".

What combination of shims is in it? What does it look like with the 010? Fiddle with the backlash some. Take a few thou out and adjust the amount of torque on the nut.

Don't try to remove material from the shim or the bearing you will not be able to keep the parallelism within tolerance. How muck shim is in there now? can you swap out different shims to getteh overall number you need? If not try the .010 shim and see where that gets you if no good hunt down a .008.

You could put that shim on a surface grinder with a magnetic table and
coolant

I've had that done on an end play shim for an N14 Cummins camshaft when I couldn't get the right one and while it will work, the magnetic table doesn't have a lot of bite on .010" so you have to go GENTLY.

Any more than a tenth or two at a time if that and the shim will walk on the table or worse.

Kevin

Seems like the easiest thing is to just get a set of shims from Raytech or Randy's.

Ring Pattern looked fairly centered on drive side, but way low on the coast side. pattern on the pinion looked low too (not even close to the large diameter part of the gear.)
I may just try the 0.010", this is one of the large shims that goes behind the pinion bearing cup. I could pull the pinion bearing. I have the clam shell type puller so I might be able to get it off without damage. I have a few of the shims that go there, might go and measure the thickness of those.

How many people on here have access to a surface grinder??? cheaper to get a shim pack!

I do.. at my brothers shop