OK. I stole the title from a previous post. Here is my sound: On acceleration, I get a driveline "tap" that sounds like it is coming from the rear. If I decelerate and mildly speed back up, I can hear it. It only happens once. On takeoff, let off the clutch and tap, just once. If I am real smooth, no tap. U-joints appear OK.  riveshaft bolts tight. Pinion has no slop and only about 5 degrees of radial play. If I rotate the driveshaft back and forth while I am under the cruiser, I think I can hear the noise coming from the 3rd member. Is this tap the slap of the ring hitting the pinion? Could it be wear between the pinion spacer and the rod that travels through it? Should I go to the trouble of pulling the differential cover to take a look? Oh yea. My driveshaft is out of phase because some careless mechanic left it that way about two months ago and I have not fixed it. I don't think that this is contributing to the problem.