Well, it took awhile but I finally got it done - Low Range 2WD Mod.

What it really does is allow me to disconnect the front hubs using a switch on the dash. Now I can use "Low Range 2WD" to move my camper around my yard and on steep campsites even when I'm on a hard surface road, with no drivetrain bind. I may also use it on steep rocky trails where I want the low range speed and control but don't need the front wheels to be pulling or the drivetrain to be binding.

Here's what I did:

First I put a switch in the dash with power feed from the cigarette lighter wire (because it was easy). Power from the switch runs through a wire to the engine compartment. I installed a waterproof 5-pin relay next to the existing "4X4 Center Axle Disconnect Solenoid" on the firewall near the battery. The "4X4 Center Axle Disconnect Solenoid" is really a hub-control solenoid-operated vacuum switch, which I'll call the 4X4 Relay (since its shorter!). I then cut the red wire that leads to the 4X4 Relay, and wired in my new relay as follows:

Pin 30 - to red wire running to existing 4X4 Relay
Pin 87A (Normally Closed connection) - to red wire running into wiring harness (runs to the PCM)
Pin 87 (Normally Open connection) - to local ground on the firewall
Pin 85 - hot wire from my new switch
Pin 86 - to local ground on firewall

When my switch is ON, the red wire from the 4X4 Relay is grounded to the body, and the wire to the PCM is disconnected. This activates the 4X4 Relay and disconnects the hubs. When my switch is ON in 4WD HI the dash indicator does not come on for some reason, but the front driveshaft is engaged although the hubs are unlocked, so I don't have 4X4. When my switch is ON in 4WD LO the dash indicator does come on, low range is engaged, and the front driveshaft is engaged, but the hubs are unlocked, which gives me 2WD LO.

When my switch is OFF, the red wire from the 4X4 Relay is connected to the red wire to the wiring harness, as before, and the PCM can ground the connection to unlock the hubs or unground it to engage them, as normal. So 4WD HI and 4WD LO both work exactly as before when my switch is OFF.

One note - I didn't try it, but I think a "quick and dirty" way to do this same mod would be to use a "quik-tap" wire tap on the red wire and run a lead to the battery ground post, either with a switch or just clamping it on when desired. I wanted the switch inside the cab, and I wanted the PCM to be disconnected from the circuit when I was activating the 4X4 Relay, just to be sure I couldn't hurt the PCM somehow, so I went with the fancy complicated method.

 

sounds like a cool little mod, but this is something i would not try in my truck

 

Ahhh... I remember when 2LO came on REAL trucks back in the day...

 

This sounds cool. Idk if I would do it on my truck. When my warranty goes up i'll do it

 

My 68 F-250 had a granny gear that literally allowed my to yank a couple tree stumps out of my front yard. I think the thing would do 6 mph with the engine wrapped out.

 

I'm surprised Ford didn't offer 2LO as standard or an option on the ESOF models, since from a technical standpoint it is so easy to do. Even the relay I added might be overkill - if I knew I wouldn't mess up the PCM then all it would take is a tapped wire running into the cab that connected to ground when switched. The other reason I went with a relay is that the switch I used has an LED in it, and it needed 12V power to light the LED. Sending power to the switch and to a relay made sure the light would light properly, so I wouldn't leave the hubs disengaged by accident.

 

Lee, for some reason the F150 crew doesnt generally accept 2wd low. Its reasonably popular on another 250/350 board that I was on, but I didnt have 4wd at the time.

I am going to study your post to see if I can duplicate your results. My yard is very sloped and there is no reason to put extra strain on the tranny for low speed manuvering when backing a trailer. I use 4x4 low after I get the truck off of the pavement but 2wd low would be a better option IMO.

Thanks for the post.

Too bad the the low range on the transfer case cant be shifted on the fly. The twin stick atlas transfer case can do RWD low/high, FWD low/high, 4wd low/high and can be shifted on the fly. At $1500+ it is not a cheap mod.

 

AND if you are only going to do it occasionally, like in your yard:

Just find and cut the red wire, and put it back together with a male/female connector. Then make a small jumper, with one connector to match the wire to the side that goes to the 4X4 Relay, and an alligator clip on the other end.

To use it, open the hood, unplug the red wire from itself, plug your jumper in to the side that goes to the 4X4 Relay, and clip the alligator clip to the negative post on the battery. Your hubs are now disconnected. Close the hood and do your chores. Restore it afterwards - otherwise you'll not only have no 4WD, but you'll also have a dead battery because the other side of the 4X4 Relay is hot all the time.

I probably got too fancy with mine, but I wanted it to be switchable from the cab, mainly so when I forget to do it ahead of time, I can just flip the switch. Plus there's no jumper to lose!

 

I posted a tutorial on how to do this, I never tried it just posted a how to within a thread where I figured out my fuse was blown and the solenoid was NOT bad. Cheap way to get better mileage around town, never thought of the reasons you mentioned.

For some reason while in 4low my throttle is very unresponsive, almost as if it's untuned again. Separate tuning for separate drivetrain conditions?

 

I'm curious to know if this will cause any problems down the road on anything, mechanical or electrical.

Sounds like something is wrong.

My truck feels like it's going to snap a driveshaft in 4LO, very responsive as well.

 

you don't have any pictures of the setup, do you?

 

I believe something is wrong. I've no idea what it could be, it's perfect in 2wd and even 4hi is fine. It definitely doesn't want to snap a driveshaft in 4lo however. Must be tuning, I'll try a new tune.

 

I don't think it's your tune. Regardless of my PCM's settings it reacts the same exact way. .

 

Well the fly by wire system is tied in with tuning, perhaps quintin may chime in. You may be right, there should be no lag whatsoever.

 

X2!!!