4X4 on 4X4 off 4X4 on 4X4 off
 

I have a 1998 4X4 I have taken it to the shop A number of times problem is that the 4X4 works intermittenly I put it into 4X4 the light comes on the unit works while in 4X4 the light goes out unit does not work I let it set over night the unit works I try to put it into 4X4 it won"t work, start up hill unit works part of the time. Thanks for the help

Vacuum leak.

Check all the vacuum lines, particularly the ones going to the front axle.

The one that runs along the bottom of the windshield under the hood is a common failure point.


phox