Torsen Differential/Friction Modifier

[SVOMACH1]

Just had a "new take off" 2013 GT500 complete rear end ( Torsen 3.73 ) installed in my 05 and the dealership added friction modifier. I read up on it and Torsen says not to add it? Opinions?? Can this harm the rear end??

[tulowd]

wont harm it but it shouldn't be in there IMO. My Truetrac works best with conventional 85/140 heavy duty fluid; much quieter than the 75/90 and hooks up out of corners way quicker and more direct. The viscosity plays some part in the performance/reaction of the torque transfer.....check for the actual fluid requirements from the manufacturer or call Ford Racing

[ZR]

Won't harm but it will underperform with it in there.
Suggest changing fluid.