So I'm going down a muddy fire road at about a 30 degree incline in 4wd. I shift into 2nd to help ease off the brakes. When I do, the back end of the jeep started to slide to the right (passenger side). I go back to drive and only use the brakes, and it straightens out.

Is this an argument for lockers? Any ideas what's going on here?

 

No, it's not an argument for lockers. The brakes are biased toward the front, which had more traction. When you downshifted and got off the brakes, the deceleration load was equally distributed front to rear, so more was directed toward the rear than had been when you were braking. Since the rear tires had little weight on them they couldn't maintain traction as well as the front so gravity was trying to pull them down the hill faster than the fronts were allowing. So, it tried to swap ends.

 

damn, and here I was telling my wife I needed to go out and buy lockers! Guess I'll have to get that new bumper / tire carrier instead to increase the weight in the rear.

 

Want me to edit my post?

 

In deep snow my JK does that. It is definitely due to lack of any substantial weight in the rear of the JK. Fully loaded it probably would be no issue