I have a 2001 Eddie Bauer Expedition with the 5.4L engine and the #$)#@! automatic 4-wheel drive system. I have a friend with a 1998 (I think) Eddie Bauer with the 5.4L and her 4-wheel drive switch has a 2-wheel drive option along with the automatic, 4H, and 4L settings. She get as much high as 20 MPG on the interstate and 16-17 MPG in mixed city/highway driving. The best mileage I have ever seen from interstate gas station to interstate gas station was a little better than 16 MPG. I'm lucky to get 12.5 MPG during normal daily driving. I know that F-150s also have an setting specificly for 2-wheel drive as well.

I suspect that a major cause for my much lower fuel economy is because I can't run true 2-wheel drive like she does. I have noticed the new 2003 Expeditions are back to having the 2-wheel setting on the dial along with OPTIONAL automatic.

Is there a way to disable the automatic engagement and get my Expedition to mechanically work the same as one with a 2-wheel setting? Could it be a simple case that the drive train is identical to the F-150 and I only need to find a new switch?

 

I don't exactly know how the F-150 and Expeditions are set up but my old F-350 Electronic-Shift On-The-Fly (ESOF) operated on the vacuum system. There was a modification to have a 2WD LOW setting by disabling the vacuum going to the hubs and only engaging the transfer case. This made backing up a trailer with a 21' truck a breeze (especially considering the large turning radius of the 4x4 trucks). You may be able to work something out like that - disable the operation of the transfer case and hubs with a switch.

Here is a LINK to see how it is done.

The site for all this was The Diesel Stop.com

 

i just went threw this on my 99 expedition, crawl under the truck right in the back of the transfer case is an electric connection, it contorlls the 4 wheel drive system, just unplug it! i went to a ford dealer and my buddy at the dealer just unhooked it and now its full time 2wd works great if it want 4wd back all i have to do is hook it back up its simple hope it helps

 

If you do decide to uplug it make sure to put some dielectric grease on the both connetor fittings so it don’t corroid or you won’t be able to plug it in and have it work again, not to mention what Ford would charge to replace the connectors…

 

Just curious, but why would you want to do that?

 

Try pulling fuse #23 in the Central Junction Box. It controls the Torque On Delay Relay. It could set a code because the GEM monitors the front the rear axle speed and applies the T-case clutch to direct power to the front wheels. If it senses a big difference and can not correct it because the relay has no power it will code. The real reason your milage sucks is the fact that the front differential does not disconnectv like the F-150 does.
Your front drivetrain is permenant. If you got the $$$ go get a front diff from an Expy that has 2WD Hi. Or an f-150.

Regards

Jean Marc Chartier

 

Thanks everyone!

So JMC, you are saying that I probably won't see any real difference in gas mileage even if I disconnect the fuse or do any of the other things posted in this thread?

 

brandonj,

Probably not. Because the front differential is always connected to the front drive shaft it has to turn when the wheels turn. The friction caused by all of this is what is killing your mpg. There is an electromagnetic clutch in the T-case. When the GEM senses a difference in the wheel speed, front to back, is energizes the clutch and the front wheels get power. For this to work the front diff must be always connected. All you can do by disconnecting the wires or fuses the is keep the clutch from engaging. The GEM is already doing that.

JMC

 

[QUOTE=JMC]Try pulling fuse #23 in the Central Junction Box. It controls the Torque On Delay Relay. It could set a code because the GEM monitors the front the rear axle speed and applies the T-case clutch to direct power to the front wheels. If it senses a big difference and can not correct it because the relay has no power it will code. The real reason your milage sucks is the fact that the front differential does not disconnectv like the F-150 does.
Your front drivetrain is permenant. If you got the $$$ go get a front diff from an Expy that has 2WD Hi. Or an f-150.

So would it be safe to say that if I change the front differential to that of an f150, that would disconnect it from that transfer case, allowing me to switch into 2wd? And speculating even further, could I then change to manual hubs to theorhetically get even better milage?

 

Using an F-150 differnetial will allow you to disconnect it from the T-case. You will also need the vacuum hoses and the solenoids and something to trigger them correctly so that the axle can disconnect and reconnect. The hubs of an Expedition and F-150 are similar to a front wheel drive car. They do not lend themself to installation of a lock unlock hub.

JMC

 

Thanks for the response JMC, assuming that I could find the parts, is such an undertaking cost-effective? Would I see a bigger jump in fuel economy?

 

I had a 99 Expy that I was trying to disable the AWD. I did run without the t-case hooked up, and I noticed alittle gas mileage difference. The problem is what everyone has said, the front diff stays connected. I even researched Ford to see if I could buy the vacuum pod that disconnects the front axle. The internals of the front diff do not have the parts needed to disconnect. So you'd have to buy a front axle from an F150 or a expy that had the 2hi option, then for everything to work right, there are 2 solonids on the firewall that control the connect/disconnect of the front axle. Then to control all of that you could do your own switch, or get a GEM from an expy that had the 2hi option. I'm not sure though if the t-case is different. You may still be able to use the one you got, but have the plug un-hooked, this is the part I'm not sure about because I traded it in on the 00 harley F150.

I can't stress enough though, leaving the front diff locked without the t-case plugged in makes the handling weird, like in the rain, the rear will slide around, but to counter steer with a locked front diff, well lets say its a bit scary. If you persue this, let us know how you make out. To help too, there are a few expy's made between 99-02 that did indeed have the 2hi option. I test drove one and it was a 00 e.b. and it had a 2hi on the switch. I asked a ford tech about this topic and he said he'd call me back with info.....that was almost a year ago!