ESOF modification

Since I've had my truck I've had mixed emotions about the Electronic Shift On the Fly (ESOF). I would have preferred a manual shift version, but this is what the truck had.

My main gripe with this system is that probably 50-75% of the time I use 4WD the front hubs won't disengage properly. I've taken the hubs apart and lightly greased them and this has helped some. Sometimes you can shift in and out of 4WD and the hubs will finally disengage. If that fails you can usually rotate the hubs back and forth between 'auto' and 'manual' and they will disengage. Once I had to remove the hub assembly (easy to do, but a pain).

The ESOF system uses vaccuum to engage the front hubs. Some people are concerned that the vaccuum has a negative effect on the sealed wheelbearings. Also, if you have a vaccuum leak, or rotted hose, or rusted fitting, the hubs might not engage when you think they are. There are seals that can go bad, and there's no way to tell if both hubs are locked.

I will give Ford a pat on the back for giving the hubs the option of 'automatic' or manual 'lock'. If the hubs fail to engage for some reason you can manually engage them. Can't do that on a GM or a Dodge.

Recently I noticed my gas mileage wasn't doing as well and the truck had some new vibrations. I also noticed a click-click-click and front U-joint binding when making sharp turns. You guessed it...the hubs didn't disengage...AGAIN! I tried shifting in and out of 4WD without success. I had to jack up the truck and see which one it was (driver's side). I was able to get it to disengage by turning the handle.

I'm gonna try something and see if I like it. I'm gonna disconnect the vaccuum source to the hubs and use the manual lock feature of the hubs. That way I'll know when they're locked and unlocked.

I traced the black vaccuum lines back from the hubs to the solenoid behind the passenger side battery. I then traced the red (source) vaccuum back to a 'tee'. I disconnected the line from the ESOF and plugged the vaccuum line.


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