'00 F350 SuperDuty

2-Wheel Drive Low Lockout

One disadvantage to the ESOF system is that you can't use the low gearing of the transfer case without engaging the front hubs. Sometimes when performing tight manuvers (backing a short trailer around, etc) the low speed would be helpful. However running in 4wd on pavement or any other surface with traction is not only nearly impossible, it's pretty hard on parts, so being able to lock out your hubs from engaging but use that low gearing can be a handy thing. This is a real simple mod.

Basically the idea is this. When you flip the truck into 4wd, a signal gets sent to a vacuum solonoid telling the hubs to lock (or unlock for that matter). What this does is interrupt that signal. The solonoid is located on the passenger side fenderwall with a three-wire connector. The red wire (on my 2000 anyway) is the signal wire that gets used. I mounted a normally-closed relay as close as possible to the solonoid, cut the red wire (extending each piece) and ran it to the switched solonoid terminals. With a normally closed relay, the circuit is normally closed and so there is no change in operation of the solonoid. To activate the system, I have a switch mounted next to the 4wd selector in the dash that powers the relay. When I hit the switch, the relay opens the circuit, then I put it in 4wd and the hubs are prevented from engaging. Then after I take it out of 4wd, I turn the switch off and everything is back to normal. Pretty easy.

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