84 k10 6 inch lift with driveline noise. Anyone know best fix?

[84Silverado4x4]

Alright I have been battling a driveline noise on my truck since I bought it a little over 3 years ago.  Complete new engine and trans, noise still there.  Completely rebuilt Np208 transfer case. Noise still there.  New front and rear drive shafts custom built to length...noise still there.  Completely rebuilt the rear end with all new bearings, motive gears, and detroit trutrac locker, noise is still there.  I get the noise at higher speeds when I am off the throttle in a cost condition but there is no noise of any kind in either accel or deccel.  It must be my pinion angle?  The t case has a half inch spacer between the frame and crossmember and the rear axle with 6" lift leaf springs have a 6 degree (I think)wedge/shim between the springs and axle.  Anyone have any ideas?
What are others using for shims with about a 6" lift?

[pneuner750]

Join the club! My 86c20 has and will continue to whine. I have the four speed manual, the rear end, clutch, transmission rebuilt. I even went as far too insulate the cabin. I still have whine. It's old, that's all I can I say. I'm with you!

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[Captain Swampy]

Take out the rear driveshaft and drive it with the front axle to narrow it down to transfer case or rear axle. Tape a plastic cup or something over the tcase output shaft.  The output shaft and the pinion should be parallel, I'm guessing your pinion is pointed up and there is less angle on the rear joint than on the one behind the tcase. The angles should be the same.

Try some good synthetic oil in the tcase and differentials. I personally use Amsoil.