I had the vacuum actuator go out on me. It is the piece on he passenger side of the axle on the back. To test to see if this is the problem remove the four bolts that hold it on. Oil will come out but it is less than one quart. remove the two vacuum lines and the 4x4 light connector. Now that you have the piece in your hands put your finger over one of the holes and try to slide the fork. If you can and hear air leaking this is your problem.