[Lowell W]

The noise speeds up with wheel speed; does it occur at the same relative frequency in any gear? Does it start immediately when you start moving or do you have to get up some speed to make it start? Does it continue until you stop? Go faster, then push in the clutch and let the car coast. Still there? Any difference with the driveline under load (acceleration/ deceleration)? While you have it up on the lift, have someone rotate the rear wheels while you look from underneath. Then pull the rear wheels and look at the backs of them for wear/rub marks. Then look in from the sides to see whether you can see something making contact with a half shaft. Sounds like something's either going around with a wheel, halfshaft or driveshaft, or something attached to one of these rotating parts (like a CV boot clamp) is flopping around and hitting something. Also look for the wear mark where the contact is happening when the noise is being made. Could be that something is being pulled out by centrifugal force as it rotates, bringing it into contact with something else. Probably not likely, but check the U-joints: turn the associated shaft back and forth while looking/listening for play.

Hope this helps. Please let us know what you find.