Gen 3 4.9 Gears (01 w/LSD) What to know?

[MoabRefugee]

Nearly ready to go the 4.9 and Ft. Locker route. Any concerns with "clutch pack" on the rear LSD prior to transfer? I have been running M1 75-90 LS since purchasing the truck, with what I feel have been great results. Some folks swear by Mitsu oil, but the M1 (diff), BG Full Synthetic SPIII(trans), and Redline GL4 (T'fer) have been awesome so far.

I have never done internal drivetrain work, aside from clutches, but I have split motocases and replaced gearsets, etc. Feedback based upon actually having performed this swap is preferred. Thoughts?

 

[Michael Brown]

I do not have 4.9 gears, but I installed a 4.3 LSD. The Mitsubishi fluid would be recommended for the clutch pack as the others may not have the right friction additives. The torsen/gear system does not care about the oil, but the fiction modifiers will allow the clutch to slip enough to build heat and engage. I just drained out whatever was there and put in the Mitsubishi SAE 90 LSD oil.