i have a '00 f250 4x4 and the front hubs are not engaging when in the "auto" position. the dash light shows "4x4;" however, i have to put the hubs in the "lock" position to get them to work. I put a test light on the wires going to the hub and don't have juice. i checked the fuse #17 under the dash and it is ok? ANY IDEAS? where is the power come from? an electronics schematic would be nice????

 

if i remember correctly, arent the hubs vacuum operated?? might wanna check some lines

 

i pulled the connector apart and can see wire leads/connector?????

 

I think you pulled the wrong thing. The easiest way i foudn to do it, go down to the local parts store, and they will have vacume testors, you just put them in the line, and they will collaps under vacume. There are two lines going down to your front hubs, one is a brake line, and the other is the vacume hose. Pull the vacume hose off, there will be a disconnect on the passenger side mounted up above the frame, and insert your will vacume testor thing, i use them because i could not hear any vacume with my diesel running, i don't know what you have for an engine, so easiest to explain it this way. If you do not have vacume, the pump is under the battery on the passenger side, or somewhere in the area. Check the connection, and take it off and test to see if you have power, if you do not have power check the fuses, and then check your switch inside the cab if you have ESOF. If you do have vacume, this process just got 100 times simpler, just take the front hubs off, take the little ring in there out and they should pull right off. Soak them in ATF, the detergents in ATF will clean everything out of there, and shoot some all-season multi-purpose grease in there and work it a couple of times. Throw the hubs back on and see what you have. If they still do not work, It is most likly the seals on the front, you can go to the loca parts store, and they can show you a diagram and you can get the seal you need

 

thank you, i guess i pulled the anti-lock brake sensors? I'll look again.

 

Service Screening Procedure: Vacuum ESOF
NOTES:

1. The ESOF locking hubs are triggered by regulated vacuum; a high of level vacuum (8.5 in-Hg or greater) engages the hubs, and a low level of vacuum (6.5 in-Hg) disengages them. Engagement is immediate, but disengagement cannot take place until after the vacuum is released. The GEM supplies vacuum for a pre-set time, then releases and vents the wheel ends, after which the hub remains in the selected mode.

2. Any malfunction in the control system (GEM, solenoid, electrical harness, vacuum harness) or a related vacuum system (climate control, cruise control) will affect the function of the ESOF hubs. It is imperative that these associated systems be certified trouble-free before testing the hublock function.

3. If the instrument panel 4x4 light is not working correctly, look for problems in the electrical system, GEM functions, or transfer case first. The instrument panel light responds to these systems, not to the axle or hubs.

If No 4x4 Engagement:

Check Vacuum Sealing at Wheel Ends

· Separate vacuum line at frame connection, just to rear of front shock absorber.
· Attach vacuum pump to knuckle side of line.
· Pump to 14 in-Hg, & watch for leak-down.
· Raise wheel on jack, rotate tire, & watch for leak-down.
· Leak-down greater than 1 in-Hg per minute indicates a sealing failure at one or more of the components on that side. Refer to workshop manual for pinpoint tests.
· Repeat for other side of vehicle.

Check Sealing at Vacuum Harness, Reservoir, & Climate Control

· Unplug vacuum harness at solenoid (double-line connector).
· Vacuum-test top hose (routing to wheel ends).
· Vacuum-test bottom hose (routing to reservoir, pump, and A/C system).
· Note: May require considerable pumping to build vacuum.
· Leak-down greater than 1 in-Hg per minute indicates service required.

Repair any vacuum leaks before proceeding further. Even if other problems exist, vacuum leaks will prevent proper hub ESOF function. Perform 4x4 diagnostic tests in workshop manual as required to locate leaks(s).

If Hubs Will Not Unlock When Dash Switch Is Set To 4x2:

· Verify hub dials are set to "AUTO" (hubs will not disengage in "LOCK" position).
· Perform all vacuum leak tests listed above. Repair any leaks found.
· Start engine, cycle dash mode switch to 4x4, then to 4x2.
· WAIT TWO FULL MINUTES to assure GEM has released vacuum.
· Rock vehicle back & forth three times (move 1 to 6 inches only) to relieve bind-up.
· Verify hub disengagement by rotating u-joints inboard of knuckle.
· Hub disengagement at this point indicates normal function.
· If hubs are not disengaged, go to 4x4 diagnostic tests in workshop manual.