still banging, u-joints OK

OK, got the 87 with the NP231 on a lift this week. Put it in 4 wheel and front tires turned freely and U-joints OK (does engage in 4 wheel), but when on the ground and wheels turned, it pops like hell. CAn the vac just not be engaging fully or can it be the dreaded time to rebuild/replace the t-case?
Dan

Sounds like a busted ring and pinion.

231 cases will bind up like that when the wheels are turned all the way and gas is applied its known as the hop basically its binding in the case due to differnent turning radius of the front and rear wheels, 242 cases have a center clutch that eliminates this with slipping like a 5 speed clutch slowly let out...I would take the shifter motor and clean it out(for the axle) when mine had trouble its because it was full of water and couldnt compress it...I would pull the cover on the diff and check for pieces though before you do anymore driving :banghead: or it could get real expensive...
themud