Now it started doing in while going forward also (to a lesser extent). I think I've narrowed it down to the rear end. Sounds like the LSD is engaging (the jerking feels like the right side). Is the left side the usual drive side until the LSD locks up? When I changed out the diff fluid with mobil1 I only put one bottle of additive in it. Tomorrow I'm going to get a second and add to it plus check the fluid level (although there are no signs of leakage). We'll see what happens. Got two weeks to figure it out before heading to Moab.