[olddog]

The drive shaft from transmission to differential should have 3-5 deg angle on the joints. If there is no angle, the rollers in the cups will never move (turn). This usually isn't a big deal with a live axle, as the axle is always moving up and down (changing the angle). On an IRS the angle is pretty much the angle. If the needles stay in one spot they wear flat spots.

I never tried removing a drive shaft from a Kirkham, so I do not know the difficulty factor. It's not all that hard to pull the caps and check the needles, once it is out. Do make sure you have a very clean spot that will not let the little buggers get lost. It is a bit harder to get then all back in place. Do one cup at a time and don't mix needles.

I'm not saying there is a big hurry to check these. Maybe save it to last. A bad U-joint will make a lot of noise when closer to a failure.