I just finished my 4" lift kit and noticed immediately that at speeds over 20 mph a slight growl would arrise after letting off the gas (to coast), the growl grows louder at higher speeds. I assumed that my driveshaft was in a bind and measured my angles of the transfer case and at the rear differential and found a slight difference, long story short, i've tried 2.5 degree shims(growl still there) and 4 degree shims and now after the 4 degree shims there is alot more noticable vibtration and the growl still persists. Any and all info is appreciated, I ifeel like its a simple problem that i just cant get pin pointed.

 

So do you think its coming from your driveshaft? Is your truck aligned? And tires balanced? Just trying to get some more information first to help out