Rear End, Suspension clanking/slap noise
 

1993 Corvette, 396LT1 A4 2800 rpm converter ,3.73 gears,D44 ( built by Ikerds). Runs great, with the exception of cruising at about 1800 rpm , plus or minus 200rpm, in OD.. It seems to buck a little, like a little surging, causing the driveline to slap, like hearing u joints are broke.
U Joints are new, 3 days ago, driveline is solid with D44,, and I cant move any of the half shafts or driveshaft by hand when in the air.
If I drop a gear, to 3rd it all goes away, even when I get in same rpm. Maybe not as pronounced due to speed, but I cant hear it.
If I keep foot on brake it takes it away too.
I posted an old thread a long time ago, but since then I put new Bilsteins, Spicers in Half shafts and driveshafts, new end links, brake pads..