98 2dr 4.3 4x4 3 button (2hi 4hi 4lo) 130k.

My 4 wheel drive has not been working since winter. just now working on it.

problem is in the front axle or front axle engagement system (engaged transfer and drive shaft locks like it should)

start vehicle, cycle 4wd/2wd. check vacuum actuator each time. does not move. take hose off, do same thing feel for vacuum. vacuum is always present (when engaged in 2 wd and 4 wd) i am guessing this is not normal.

where do i need to start to get this problem fixed. and what should the vacuum be (on or off) when in 2 HI and 4 HI

 

This thread has been monumentally helpful with my 4WD slow-to-disengage issues.

4wd Front Axle Clicking - Goes away in 4HI or LO

My transfercase switch was stuck in the open position and the cable going from the actuator to the front differential was seized. I also had vacuum while in 2HI with the engine running. The new switch solved this issue.