Re: 4x4 won't engage. 2001 Ford F-150. front axle...
If you know that the actuator on the front of the truck is good check the wiring for any breaks. If it is anything like my truck the wires on the front actuator should run to a switch on the top of the t-case. If you cant find a break in the wires running to the t-case your problem is most likely the switch.
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I am a bit rusty on the 22 year old part. Someone else may be more informative, but on some of the 4x4 actuators they used different methods of moving the internal parts.
The actuator used to be Vacuum operated and the part would move a certain distance to put the transfer into high or low mode. If the actuator did not fully extend or contract you would be between gears; sort of in Neutral.
You are now faced with the front driveshaft free-wheeling(But which end?). Disconnect one end of the front driveshaft so you can feel whether the transfer case is free-wheeling or if the other end of the shaft is turning anything in the front axle. With the front hubs locked, the front driveshaft should not turn or if jacked up, the tires should spin when the front driveshaft is turned by hand.
When you are assured that the front axle is fine, then the problem can only be the transfer case. I remember people had a lot of trouble with the actuators.
I hope this gives you a way to test which end of the front driveshaft is the problem.
There are some Blogs on the internet like Ford4x4Owners.com and Off-Road Blogs which can be very helpful. I hope my suggestion helps.
The 4x4 system on an 88-98 full size gmtruck is controlled electronically except the shifting of thetransfer case which is done with a lever. When the transfer case isshifted into a 4x4 gear a switch in the upper driver side of thetransfer case is closed this sends power to the front axle actuatorwhich engages the front wheels to the front axle. A sensor is alsolocated on the front axle which is closed when the actuator shiftsthe axle into gear.
The first thing to check is the 4x4fuse if it is bad replace it. Next check the switch on the transfercase connect a continuity tester to the switch and shift the transfercase into 4x4 the stitch should close, if it dose not replace it ifthe switch is functioning properly replace actuator on front axle
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. I would guess a problem with the vacuum disconnect motor on the front axle ( or vacuum lines from teh solenoids or the solenoids themselves ), but best to verify the test above to know which way to go. Post back a comment after the test.
This is for 4x4 shifter on the floor.
In the front of the truck on the axle there's a plastic cover with 2 10mm bolts remove it and spray down the shifting actuator it operates on vacuum. You might have to pull it in four wheel and check to see if the vacuum pod is engaging the shift lever on the axle. Then again you might have to replace it very easy to do. But I would spray it down with some WD-40 it should work.
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
there is no pressure /vacuum required to lock the axle
the action is the actuator moves a dog clutch that positively engages the gears
so is the problem else where
maybe broken axle , wheel locks are not engaging
lock it in and jack up and see which part isnt locked
transfer, front end
front end uses vacuum actuater
and transfer uses a electric motor
front driveshaft shouldnt turn when in park and front wheels off the ground
front wheels shouldnt turn with one wheel up
shift into 4wd and move truck a couple of feet.
if light is still off, park truck block the wheels set the park brake jack right front wheel and try to hand spin the wheel if wheel doesn't turn 4x4 is functioning properly but there is a wiring problem use an ohmmeter to check the 4x4 switch wiring fuse and bulb
if wheel turns freely the front axle or transfer case is not engaged
attempt to hand spin the front driveshft if the driveshaft will spin the transfer case is not engaged check the transfer case shift linkage, problem is in linkage or transfer case internals
if the driveshaft will not spin the transfer case is engaged properly
with trnsmission in neutral or park start engine measure vacuum on the two vac lines at front axle shift motor . one line should have approx 20" vacuum. other line should have none
if no vacuum measured look for vac leak or bad vac switch
if both lines have vac look for a bad vac swithc or ruptured cad actuator diaphragm
if one line has 20" +- VAC
move transfer case lever to 2wd measure vac again lines should have swapped vac signals
if no vac switch bad or 4wd shift likage needs adjusting
if yes vac motor bad or stuck or shift fork stuck
remove vac shift motor from the axle attach vac lines to shift motor engage disengage 4wd
does shift motor plunger move at least 1/2 inch
no shift motor bad
yes check axle shift fork and vac motor for binging