Well working on a 90 chevy again. I just put new halfshasts in it. Worked good for a couple times i needed it. Only used to get outta light snow. Went to put it in 4x4 today and nothing. So I pulled all the connections on the diff to check them out. All turned out fine. Front driveshaft is spinng. I had in in 4x4 on gravel rd after like 50 mph there is a noticable vibration! When its in 4x4 the halfshafts dont move and the 4x4 light inside the cab doesnt light up at all. Please tell me the weak diff didnt give out! Need anymore info let me know!