My 4-wheel drive is and my 2-wheel drive is broke on my 88' jeep cherokee , How much will it cost to fix?

what are most likely the parts broken?|||on the front passengerside axle there is a shifter that engages your 4 wheel drive . it is opperated by vaccum hose. when it rusts out there is little to do but replacement. i chose "4x4 posi lok" its about 150.00 and a 15 min install in driveway. gl|||You don`t make any sense. what doesn`t work ? 4 wheel drive, or just the 2 wheel drive? Could be a tranfer case problem, broken axle,linkage problem. Loose nuts behind the wheel are the most common problems