I too have a shifting prob which seemed to just start while on my trip in
Colorado last week. When I'm on the interstate and pass over a bridge or
concrete
barrier along the highway such as in a construction zone, I can hear a
faint 'whirring' sound. This seems to only happen when the gas is applied
and at 40mph or faster.
If I let off the gas, it goes away.

Also, I noticed when I let out the clutch without much gas or in reverse,
the back end will shudder a bit. This is not to be mistaken with not
having enough rpm's when letting the clutch out. It seems if I don't put
that much pressure on the clutch by giving it a bit more gas, this won't
happen. BTW, the trip was flawless on the 3000 mile round trip from Wisco
to
Colo, especially in the mountains. Otherwise it shifts fine.

smanning
'84 westy