I swapped in a clutch style diff. into an open 741 case. 3:55 in 4 spd.A body . Set the backlash at what I measured to be .007 @ tightest spot{maybe I F`ed up } . When rear reachs operaring temp there is a gear wine under slight load it is not as noticeable when cold and was not there prior to installing unit .Is this noise due to the back lash being off{I would guess as that should be only change ? Does the hot vs cold tell if I have too much or Not enough lash {I did not touch the pinion gear} . Original back lash was not noted.

It's because the backlash is different than when you took it apart.

dulich(sp?) suggested sawdust

I'd pull it immed & reset it & hope you get it clos(er) to where it (originally) was b 4 it beds in to the pattern that you set it to when you added the sure grip. they say it's hard to totally quiet a noisy set but might make some improvment & I'd get on it asap & hope for the best. Do ya feel lucky, well do ya. EDIT look up the rear axle troubleshooting charts for a whine on accel & see if the backlash needs to be increased or decreased. Might get you in the right direction. Really needed the orig backlash figure at the tightest point b 4 dissassembly