1992 Jeep 4 wheel drive vacuum line for front axle

Your front end is engaged with a vacuum line . make sure the line is good. You will find it comeing off front axle.

Operationally vacuum shifts the front axle between 2WD and 4WD mode. The GEM ( Generic Electronics Module ) applies ground to the solenoid needed for the mode selected on the switch ( for ESOF ) or when the transfer case shift lever is moved ( MSOF ).The contact plates in the transfer case signal the GEM that the transfer case is engaged, and the Vacuum solenoids need to be activated ( either 2WD to 4WD or 4WD to 2WD ).

Lift and support the front of the truck so the front wheels are off the ground ( take safety precautions, chock wheels, jack stands, etc )
Key on, engage 4x4 and try to turn the front drive shaft.
- If it turns it is a problem with the transfer case.
- If it doesn't it is a front axle engagement problem ( this is what you seem to have, the transfer case is engaged and will drive the front shaft mine was a key on engine off test ).

- If the front drive shaft does not turn :
•With the truck running ( with front wheel back on the ground ), switch from 2WD to 4WD and back again, the vacuum shift motor should move the lever on the front axle.

-- If the vacuum shift motor does not move:
1.Check for vacuum on the lines while shifting between modes. Pink vacuum line is 2WD mode, Light Blue vacuum line is 4WD.
2.Check the fuses for the 4WD system and the solenoids.
3.Check the vacuum lines from the vacuum shift motor to the solenoids on the firewall.

4.Check the vacuum lines from the solenoids to the vacuum reservoir box behind the battery.
5.Check the vacuum reservoir box for cracks.
6.Typical solution is the vacuum lines ( to the solenoids or to the vacuum shift motor ) are cracked or the vacuum shift motor has a cracked diaphragm and has water in it.
7.Could be the shift plate contacts in the transfer case are corroded / not making good contact, and not activating the solenoids.


Usually the case is cracked vacuum lines from the solenoids, the next common is a cracked vacuum reservoir box, and 1 time I have seen the mount for the vacuum disconnect motor broken ( motor floating free so it could not push against the axle )

Is it a an 85 or a95? I know of two switches on these vehicles, one is a four port vacuum switch on the top of the transfer case, you must unplug the vacuum line, and unscrew it from the transfer case. The other is on the front axle. The one on the transfer case is rather difficult to reach, it is hex shaped for a wrench. Unsure of size, it is large though. The one on the front axle is part of the axle shift motor, is unplugged and removed for replacement. I believe the one on the axle only serves to turn on the 4x4 indicator light.

i just boought a 1992 Jeep Wrangelr sport with a chevy 305 V8 and its a automatic with a standard 4 wheel drive and i put in 4 wheel drive and the front tires wont move what is wrong????

actually that first soultion is wrong it is correct on smaller pickups but on the full size pick ups they use a differnet sytem
there a electric actuator on front axle
there be two elctrical plugs on front axle u want the bigger of the two other one is just to turn the 4 wheel drive light on
un plug actuator then remove actuator after it removed plug it back in but leave it out of axle turn key on and shift down to 4 wheel drive the actuator should move out if it dont that your problem if i does move this isnt your problem it either the tranfer case or in front axle

I think the 94 wrangler still has the splice front axle with the vacuum control. It is located on the front axle on th pass. side . It is a large unit and is easy to see. Check vacuum lines.

vacuum originates at manifold but goes to a storage tank and is sent to axle through a switch control.

Your 4-wheel drive is activated by a vacuum mechanism located on the front axle. That has probably failed or it could be the vacuum line.

Our Jeep Wrangler YJ's are equipped with a vacuum module on the front axle. It is used to engage the front axle when the transfercase is shifted into 4WD. Check the vacuum lines on the front axle to make sure they are connected. The passenger side axle shaft has a disconnect sleeve that is moved left and right by the vacuum.

I do not have a vacuum diagram for the 89 Cherokee, but my 89 had the same issue several times and all it was is that the block of vacuum lines that go into the front axle on the rear of the axle on the passenger side of the vehicle. I ended up having to put a zip tie around the axle and hose block to hold it on. Have not had the issue again since doing this. Hope that helps.