Power as in 12 V DC ? if yes, you are not in the correct area, the front axle is locked in and out of 4x4 mode with vacuum.
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.
- 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.
Item #10 in this diagram
I can not get power to the motor to engage my - sscullys_10.gifads/images/sscullys_10.gif" alt="sscullys_10.gif" class="h_mi" />
-- 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 cI can not get power to the motor to engage my - sscullys_199.jpgactivating the solenoids.
- If the front drive shaft turns:
For ESOF system
-- Check the fuses for the transfer case, engine compartment fuse panel, 17 & Cab fuse panel fuses 13 and 23 ( verify with owners manual, 97-97 & 99-03 MY can be slightly different on some items ).
-- Try hitting the transfer case with a dead blow hammer ( do not use a metal hammer, it can damage the transfer case ) to see if the transfer case shift motor is hung up .
-- Check the transfer case connector, to make sure the connector pins are clean and making good contact.
For MSOF systems
-- Check that the shift linkage on the transfer case is moving when the lever is moved from 2W to 4H and 4L.
SOURCE: 2001 Trooper: Front axle will not engage when I press dash 4x4 switch
hi guys i would check all the small vacume pipes that conect the sol valves toi the vacume actuators having just replaced the engen in mine i found that these do not have any clips holiding them on tight and can get oil on them and become oversized and leak you can test the diaframes in the actuators by putting a length of pipe on one port and sucking by mouth you can hear the actuator move and then find you can put toung on end of pipe and it will hold a vacume if it does not then chances are the actuator diafram id u/s hope this helps bill
SOURCE: 1990 GMC Sierra 4x4 1500
the connections near the front axle that activate the motor to engage the system aren't melted? That's a comon problem for that body style. If there good, sounds like it could be that motor itself. To figure out if it's you motor or transfercase, jack up the rear end, have a friend inside shift into 4 wheel drive, or try to, and put it in gear and apply some gas. If the front driveshaft is turning then it's something with the front end. If not, farther back in the system.
SOURCE: front axle - front drive shaft Toyota tacoma 1998 4x4
more than like have a broken axle shaft, un hook the rear drive shaft and put it in 4wd if it wont move then you know you got a broken axle shaft or spider gears broke in the pumpkin
SOURCE: 4x4 not working when i shift it in 4x4 auto trans
Find the accuator on the front axle it has a two wire pigtail and threads into the axle housing. Check for power and ground if you have both when the transfer case is in 4x4 the replace the accuator. They are available at most parts stores and are a very common problem. Let me know how it goes.
SOURCE: 1998 ford ranger 4x4 Front Axle hubs will not engage
I found a website that explaned that you can remove the hub and dust cover, inside is a spring which holds the hub out, removing this spring and replacing the rubber dust cover and hub will lock your front hubs in continious. as is done on later models, This has worked for my 98 4wd
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