Here is an automatic transmission problem I was hoping someone could help
with.
Every so often, when the AT is shifting (from 1st to 2nd? but I'm not
sure), I feel a clunk and sometime a little bit of grinding.
This tends to happen mostly when I'm accelerating up a hill from a very
slow speed (e.g., after a turn) and I think mostly when the vehicle is
warmed up.

And here are some other possibly relevant symptoms:
1.  Universal joint may be getting loose.  For example, sometimes I get a
little clank when starting up.
2.  There is often some whining when I first start up cold in the morning,
but this subsides shortly after I pull out of the driveway.
3.  There is some vibration in the shift linkage.  It makes an annoying
buzzing or rattling sound near the dashboard on acceleration, but goes away
if I just put my hand on the AT shifter knob.

The only thing I've done so far to investigate is to check the AT fluid
level.  It was a little low, so I topped it off, but that did not make any
difference.

The vehicle is a 1986 Wolfsburg Westfalia Weekender with about 100,000
miles on the engine, and about 50,000 miles on a new used final drive.

Thanks.