I'm driving a friends 87 Westy, trying to figure out where driveline
noise is coming from.

There is a noise coming from right rear area whenever throttle is
applied.  However, when I let off the gas, the noise goes away (or at
least gets much much quieter).  Engine runs fine, noise must be
coming fron transaxle, driveshafts, wheel bearing/brakes.

Anyone seen these symptoms?  Where should I start looking?