I have the exact same set up as you except. The rubicon drive shaft. I did have that problem except in first and reverse it ended up being the transfer case was messed up. Try putting it in 4 hi and 4 low and see if it still does it?
92YJ 2" BDS Lift, 34'' TrXus MT's Metalcloaked, NV3550 ford 8.8, built 4.0, Comp 4x4 Cam, Diamond high comp pistons few other bolt ons
When was the last time you got an adrenaline rush at 3 mph?