I have a 2005 2500HD CC D/A 4x4 with about 4000 miles. I love it. I am planning on towing my 8k lb. TT about 1700 miles in October. I am planning on changing out the rear diff fluid and I was wondering whether to use the limited slip additive to the oil. I plan to use Amsoil Series 2000 Syn. 75W-90. 1) Do I use the limited slip additive? 2) How much fluid is recc? (Dealer seems to be unaware of TSB's) and 3) Do I change the rear diff fluid before or after the lengthy tow trip (or both). Thanks in advance. Jim.
