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Front axle won't engage in 4x4
Thread Starter
Junior Member
Joined: Feb 2010
Posts: 32
Likes: 0
From: West KY
Year: 1990
Model: Cherokee
Engine: 4.0 I6
Front axle won't engage in 4x4
Ok,went wheeling the other day and found out i've got a problem. My front axle won't engage. I'll put the xj in 4hi or lo, i can hear it lock in and the 4x4 light comes on the dash, but when i go up tha hill, front wheels won't pull for about 95 percent of the time. I tried it multiple times and one time the axle did engage and go up the hill no problem. Any idea what this is? Its got a brand new transfer case, so i doubt that's the problem. the vacuum actuator on the front axle of the passenger side is loose and has some wires hanging out, i taped those back up but haven't had a chance to test it out again since. Even if the vacuum actuator wouldn't work, wouldn't the front driver side wheel still pull? Anything else it could be?
Seasoned Member
Joined: Feb 2010
Posts: 298
Likes: 1
From: so cal
Year: 1990
Model: Cherokee
Engine: 4.0
If the actuator has wires hanging, It will not work. And actually those are vacuum lines. Those actuators are always a pita. You will probably have to replace all the vacuum lines.
You say it is a 1990, thats wierd, mine is a 90 and doesnt have a actuator.
You say it is a 1990, thats wierd, mine is a 90 and doesnt have a actuator.
CF Veteran
Joined: May 2009
Posts: 10,426
Likes: 61
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
The actuator is there to connect the passenger side axle with the differential. If the actuator does not work, there will be no power going to the front tires.
I would reconnect the vacuum lines (there not wires, theyre vacuum lines) if they are not and test it. If the actuator is bad you could:
- Replace the actuator ~$90
- Buy a Posi Lok kit ~$200
- Lock the actuator over, FREE
- Change the front diff/axle to a 91+ model.
They stopped using the Disconnect in 91
Last edited by 89Laredo; Mar 16, 2010 at 07:25 PM.
Seasoned Member
Joined: Feb 2010
Posts: 298
Likes: 1
From: so cal
Year: 1990
Model: Cherokee
Engine: 4.0
No..
The actuator is there to connect the passenger side axle with the differential. If the actuator does not work, there will be no power going to the front tires.
I would reconnect the vacuum lines (there not wires, theyre vacuum lines) if they are not and test it. If the actuator is bad you could:
If you have the "full time" TC there will be no actuator. Or someone could of swapped it.
They stopped using the Disconnect in 91
The actuator is there to connect the passenger side axle with the differential. If the actuator does not work, there will be no power going to the front tires.
I would reconnect the vacuum lines (there not wires, theyre vacuum lines) if they are not and test it. If the actuator is bad you could:
- Replace the actuator ~$90
- Buy a Posi Lok kit ~$200
- Lock the actuator over, FREE
If you have the "full time" TC there will be no actuator. Or someone could of swapped it.
They stopped using the Disconnect in 91
Thread Starter
Junior Member
Joined: Feb 2010
Posts: 32
Likes: 0
From: West KY
Year: 1990
Model: Cherokee
Engine: 4.0 I6
Ok, is there a way to tell if the vacuum system is shot?
If I understand correctly, if the actuator isn't working, both the drivers side and the passenger side wheels won't pull?
I've read good things about the posi-lok system... what about install? is it a pain or relatively straightforward?
I tell ya, cherokeeforum is priceless to newbies like me! to you experts, thanks for the patience and advice!
If I understand correctly, if the actuator isn't working, both the drivers side and the passenger side wheels won't pull?
I've read good things about the posi-lok system... what about install? is it a pain or relatively straightforward?
I tell ya, cherokeeforum is priceless to newbies like me! to you experts, thanks for the patience and advice!
CF Veteran
Joined: May 2009
Posts: 10,426
Likes: 61
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
AXLE SHIFT MOTOR FUNCTIONAL TEST
1) Raise vehicle. Disconnect vacuum harness from axle shift
motor and connect a vacuum pump to vacuum shift motor port. See
Fig. 2.
2) Apply 15 in. Hg. (51 kPa) of vacuum to front port and
rotate right front wheel to fully disengage outer and intermediate
axle shafts (i.g., into two wheel drive operation).
3) The shift motor should maintain vacuum applied to front
port for a minimum of 30 seconds. If motor does not maintain vacuum,
replace it. If motor does maintain vacuum, proceed to next step.
4) Disconnect vacuum pump from vacuum shift motor front port.
See Fig. 2. Connect vacuum pump to vacuum shift motor rear port, cap
port for indicator lamp sw., and apply 15 in. Hg (51 kPa) of vacuum to
rear port.
5) The shift motor should maintain the vacuum applied to rear
port for a minimum of 30 seconds. If shift motor does not maintain
vacuum, replace it. If motor does maintain vacuum, proceed to next
step.
6) Remove cap from port for indicator lamp sw. and determine
if vacuum was present at this port. If vacuum was present, the shift
motor functions normally. If vacuum was not present, proceed to next
step.
7) Apply 15 in. Hg. (51 kPa) of vacuum to shift motor rear
port. Rotate right front wheel as necessary and ensure that outer and
intermediate axle shafts are completely engaged. The axles must be
completely engaged (i.e. into four-wheel drive operation) to open port
for indicator lamp switch.
8) Determine if vacuum is present at port for indicator lamp
switch again. If vacuum was present at por, shift motor functions
normally. If vacuum was not present at port, replace shift motor.
1) Raise vehicle. Disconnect vacuum harness from axle shift
motor and connect a vacuum pump to vacuum shift motor port. See
Fig. 2.
2) Apply 15 in. Hg. (51 kPa) of vacuum to front port and
rotate right front wheel to fully disengage outer and intermediate
axle shafts (i.g., into two wheel drive operation).
3) The shift motor should maintain vacuum applied to front
port for a minimum of 30 seconds. If motor does not maintain vacuum,
replace it. If motor does maintain vacuum, proceed to next step.
4) Disconnect vacuum pump from vacuum shift motor front port.
See Fig. 2. Connect vacuum pump to vacuum shift motor rear port, cap
port for indicator lamp sw., and apply 15 in. Hg (51 kPa) of vacuum to
rear port.
5) The shift motor should maintain the vacuum applied to rear
port for a minimum of 30 seconds. If shift motor does not maintain
vacuum, replace it. If motor does maintain vacuum, proceed to next
step.
6) Remove cap from port for indicator lamp sw. and determine
if vacuum was present at this port. If vacuum was present, the shift
motor functions normally. If vacuum was not present, proceed to next
step.
7) Apply 15 in. Hg. (51 kPa) of vacuum to shift motor rear
port. Rotate right front wheel as necessary and ensure that outer and
intermediate axle shafts are completely engaged. The axles must be
completely engaged (i.e. into four-wheel drive operation) to open port
for indicator lamp switch.
8) Determine if vacuum is present at port for indicator lamp
switch again. If vacuum was present at por, shift motor functions
normally. If vacuum was not present at port, replace shift motor.
I dont have Posi lok, Too expensive for what it is. IMO But the install is pretty easy.
You can make your own, Ill find a writeup for you.
Writeup:
http://www.jeepforum.com/forum/f12/h...5/#post5585559
Last edited by 89Laredo; Mar 16, 2010 at 07:48 PM.
CF Veteran
Joined: Mar 2009
Posts: 1,208
Likes: 1
From: Watha,NC
Year: Jeepless at the moment
the passenger side shaft is the two peice shaft, that said the front is an open differential meaning the wheel with the least traction gets the power so if the actuator is not engaging all the power is going to the inner shaft. For the price of the of the posi lok you can get a non disco axle
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