8.8 rear takes almost three quarts fluid.Iused royal purple 75-140syn.Already has LS additive in it.Used syncromish in TC instead of trans fluid,A little more protection.

 

My Chilton's manual recommends draining the rear end fluid from the filler whole first, then taking off the cover and cleaning out the grime inside. Put the cover back on, then fill through the hole. Make sure you add the appropriate friction modifier for posi.