Rearend Noises

This may sound too simplistic but could they be using the wrong type of gear oil? I know torsen units don't require any friction modifiers unlike the clutch type limited slip units so they may be using something too light for the diff because of that. When I had my 240SX I installed a helical/torsen type LSD and ran it with Redline heavy shockproof oil. Operation was cool, smooth and most of all QUIET.

M-4204-F3180(2) 8.8" 31 spline Open Differential
M-4204-F288(2)(3) 8.8" 28 spline Traction-Lok
M-4204-F318(2)(3) 8.8" 31 spline Traction-Lok
M-4204-F318C(2)(3)(6) 8.8" 31 spline Traction-Lok
M-4204-C75(2)(3) 7.5" 28 spline Traction-Lok
M-4204-A28(2)(3)(5) 8.8" 28 spline Auburn HD
M-4204-A31(2)(3)(5) 8.8" 31 spline Auburn HD
M-4204-P31(2)(3)(5) 8.8" 31 spline Auburn Pro 2
M-4204-R31(1) 9" 31 spline Race only – Detroit Locker
M-4204-T28(4) 8.8" 28 spline T2 Torsen Differential
M-4204-T31(4) 8.8" 31 spline T2 Torsen Differential
NOTES:
(1)Off-road use only!
(2)Will accept anti-lock exciter ring.
(3)Requires 4-ounces of CM-19546-A1 friction modifier with initial fill.
(4)M-4204-T28 fits 1999 Cobra/Thunderbird/Mark VIII with IRS (2001-04 Cobra has 31 spline).
(5)Recommended for street use only.
(6)Fits 2003-04 Cobra.

If you used F288 diff for Traction-Lok, as you can see by the foot note number (3) it requires friction modifier.

As a side note, some gear oils already have the friction modifier added to them like Royal Purple.