30 dnt, was driving fine after repairs from a big crash. All of a sudden all 4 wheels lock up. Was as though the brakes had come on but they hadn't. The drive shafts from the center diff wouldn't move at all. I figured the center diff must have broke but i've taken it off and it looks fine. Without the diff in everything moves freely, I took the diff off and it also turns ok. Thought i'd take the center diff off and it would be locked up but it wasn't. Got the diff draining i'll take the opportunity to change the oil. Maybe i'm missing something obvious ? I can't think what.