I recently disassembled the differential on my 15 touring and found something unusual on the spider.
As you can see there appears to be small shims on each of the 3 spider legs. These are NOT on the spider gear bearing surfaces but rather on the "legs" of the spider where they rest in the case. I assume they were put there because there is a little slop where the legs fit in the case.
How important is it to have the spider legs tight in the case?
Below is a pic of pieces of the remaining shims.
Without even looking in the book, I bet it tells you to ditch that sucker. It seems to me I remember reading that that kind of wear is unusual, which means there should be plenty of better ones around.
It is fairly important for the spider to be a tight fit in the housing Otherwise, it will eventually wallow out the holes and cause a problem. I'm not sure as to why yours were worn to begin with. There's no movement there, so there should be no wear.
The only thing I can figure is that sometime in the past, the differential housing had gotten loose, allowing the spider to move around a bit, eventually wearing out the holes. Someone tried to shim them to make it tight again.
I'd personally just find another case (and spider if those legs are worn). They aren't expensive, and clearly something was wrong to begin with.
Looking at the gear-bearing surfaces, those appear pretty worn too. Have you measured them?
All the above plus, The spider gears are similar to the planetary triple gears in the transmission, in that they are all engaged at the same time, and so, they must all mesh together for minimum wear. If the shims cause the spider to be rigid in such a position that the gears are not evenly meshed, it will cause excessive wear on the gears or the bearing surfaces of the gears. Depending on how good you want your restoration to be, it calls for replacement of all the worn parts. It would be better to replace everything as is, than to replace the gears and not the spider, because right now everything is worn to fit, and if you put in new parts with the old ones, it will cause excessive wear until everything wears in again.
I didn't realize that Chaffin's book gave spider tolerances. The spider stubs should be .622 and mine are .605. So I guess there's a new spider in my future.
The good news is that when I clamp the spider between the two halves of the case there is about .017 of clearance. So I'm thinking that a new spider will fit in the cases tightly and the cases are OK.
The gears themselves are well within spec and show no signs of uneven wear.
I'd find another spider and diff case. As far as the gears go, I'm sure there are some specs, but the gears don't even move unless you are going around a curve. Unless they are real bad, I wouldn't think twice about reusing them.
Bud, the spider should be a snug fit once the two diff cases are bolted together. It should not move but, every one I've ever taken apart does. It's easy to see how they become loose as all driving and braking forces are applied to the differential case and spider and overtime the holes in the cases get spread and spider wears. I have a box full of spiders and cases and match them up until I find a set that fits best.