My 4WD will not disengage. I have the switch on the dash and manual locking hubs. In messing with it I also got the 4 wheel low stuck as well. By messing with the hubs I finally got the 4wheel low to disengage but the 4 high is still on.

I drove with the hubs in "auto" today and the light was still on. WHen I need the 4WD I had to flip the hubs to lock. The light on the dash stays on regardless. Any ideas?

 

do you have the shift on the fly **** on the dash or the shifter on the floor?

 

Howdy and welcome to the forums! Also welcome to one of the strangest 4x4 systems on a ford truck, the Superduty's Electronic Shift On the Fly (ESOF). Good in theory, but just a heck of a lot more relyable to keep it simple.

Basicly this is the operation.

The dash switch in the 2WD positon has the transfer case simply send power to the rear wheels. Also if the hubs are placed in the AUTO postion, the ESOF computer has the hubs unlocked by vacuum control pulses.

The dash switch in the 4x4high positon has the transfer case send power to the rear wheels and front axle with the transfer case shifting motor. If the hubs are placed in the AUTO postion, the ESOF computer has the hubs locked by vacuum control pulses.
4x4high can be engaged/disengaged in any gear, stopped or moving. I like to be stopped for the least amount of stress on the system.

The dash switch in the 4x4low positon has the transfer case send power to the rear wheels and front axle at a geared reduction with the transfer case shifting motor. If the hubs are placed in the AUTO postion, the ESOF computer has the hubs locked by vacuum control pulses. 4x4low can be engaged/disengaged only with the shifter in neutral, brake pressed, and not moving.

The usual failure is the vacuum controled hubs. Thankfully we can lock them in manually. Other failures could be the electrical controls, shift motor or the transfer case itself. Is it actually in 4x4, or is just the light on. Can you take a tight turn easily?

Adrianspeeder

 

I have the switch on the dash. The light remains on with the switch in 2WD and the hubs turned to auto.

In this mode I can make a turn easily without the hopping common when engaged in 4WD.

I have always wondered why the hubs have an "auto" selection. When in this mode and I switch the dash control to 4WD nothing happens. Why not just call it "free" and "lock" like in the past?

I stopped at a garage yesterday and they thought it might be an electronic issue with one of the sensors or connections to the transfer case.

In your reply you indicated a vacum line possibly may be off. Where would I find that?

I appreciate the help.

J

 

I've got a 1998 F150 4x4 5.4L Shortbed with about 130,000 miles. Its got the Shift-on-the-fly and automatic hubs.

Recently got some snow and thus discovered an issue. I can shift into 4H the indicator comes on in the cab and when I turn sharply I feel it jumping, it also seems to shift into 4L as that turning issue goes away. However when I shift into 2H from 4H or 4L the light goes off yet its still difficult to turn and such (I can hear what sounds like the front drive axle going). If I stop and back up maybe shift into park or neurtal it will finally shift out of 4H and then back into 2 H.

I got under the truck and the shift arm on the actuator moves, so I think that is free. I looked at the vaccum cables and they look okay from a glance. Is the diaphram on the actuator a 2-stage or 1-stage, as I am wondering if its bad?

Could one of the selonoids/vaccum switches be bad? I tried to order one from the local NAPA and they can't find one, they think its a dealer part only.

I was thinking about buying new vaccum lines, yet the same NAPA dealer did not have lines specific to my truck.

I'm new at the 4x4 repair, so any help would be appreciated! Also, any diagrams on the 4x4 or vaccum lines would be also great.

Thanks!
Kevin