84 with diesel 5sp and inline four VW motor.

Very intermittently, after coming to a complete stop then turning left and accelerating, my Vanagon sometimes makes a kinda scratchy buzzy noise.  Sounds like it is coming from the right rear, almost like a tire is rubbing on something..As soon as the direction of travel is straightened out, the sound goes...The  sound has come about 5 times over a month or so.  The interval between episodes is not increasing..Totally random times, though twice it has come at the same corner..which is on my way anywhere...
  I had the wheels off, balancing the tires, after two of these sound episodes and didn't see any rubbing on any tire. I pulled on the wheels to check the wheel bearings and they felt ok, though the rears did have a little lateral play (in and out perhaps as much as a few millimeters)   The drive, how the van feels when this noise happens, is normal.. No binding feeling, no big vibration...just that weird noise.  If this was my racecar, I would be thinking Limited slip diff is acting up, or the wheel is rubbing, or someone rammed me in the rear...About 6000 miles ago, I changed tranny lube to full synthetic..The clutch feels normal, the shifting is ok, the ebrake is ok, though I have to really reef on it to hold the van on a hill..
  Anybody have any guesses where I should start looking? Besides jacking it way up and eye-balling the right rear for obvious rubbing or something loose that is swinging over into the tire, somehow...?
 Thanks, Don Hanson