rear pinion angle 4" lift blocks?

[cst 72 blazer]

ok i have an 89 and a 90 both with blocks in the rear.i had a growl in the rear of the 90 once i added 3/4 axles.to solve problem i droped the t-case cross member 1 inch with those spacers that came on the blazers..the 89 is a half ton and made a slight growl runnin round 55mph so i tryed the cross member drop and it cured the problem in foward but now makes a very odd sound in reverse? any good ideas?