Ok I pulled fuse 104 from under the hood on my 99 and i cant tell that it made any differance. the truck still bogs down at lower rpms, dont hear any wheel spin. I did notice once the 5.4 gets to about 4100 rpm it starts takin off. So either my tuck has lost all low end power or i did something wrong.

 

So you disabled a system that during normal driving is doing nothing, and you now get better mpg. Are you reading what you are typing? What do you attribute the milage increase to?

 

This is going from memory, but when I 1st got my Expy in '01, I was on a different forum and there was a guy there that worked for Ford. He stated that the Expy in AWD has a minimum of 5% of power going to the front wheel, but when it senses the rear spinning faster, it would transfer more power to the front. So for those that think AWD is 2WD when there's no rear wheel slip are wrong. The clunking happens when there's a sudden increase in power to the front.

BTW, this guy, I wish I could remember the forum and the guy's name ... was the one who eliminated a pulley from the original 5.4L in the Expy. Take a look at the pulleys on the 1st year of the Expy and you'll see that later models are a pulley short.

 

Somebody is a pulley short alright

If you look up the technical specs of the t-case, as published by the manufacturer, Borg Warner, you will find that it is designed to be disengaged when relative wheel speeds allow. This is a pretty simple wet clutch engagement using an electric solenoid. There is some variable positions in the engagement but it is by no means a sophisitcated full time or all wheel drive system. This is a part time arangement with automatic engagement. If it were set up for 5% of the torque going forward at all times you would be requiring the engagement clutches to be slipping at all times, everythime you make a turn, those clutches would have to slip. If that were the case, I doubt this would be a long lasting component.

 

very good information... i plan on doing this switch mod to mom's truck...

 

Pretty much a waste of time to pull the relay to disengage the AWD. I did it for a couple of months and found no real difference in power or MPG.

 

I am not sure if there was any changes with some of the Expeditions through the last few years but based on my 98 and 99 models, I am not understanding what the original fuss was all about with the A4WD when if you dont want it, dont switch to it. I myself dont, when I need 4wd, I go to 4 hi and in 4 low when needed.

 

I don't know when, but Ford made a slight change to the 4WD system in '99 or '00 so some of us have A4WD, 4WD Hi or 4WD Lo with no 2WD option. Some of us like to have the 2WD available to us if and when we want it. That is the reason for pulling the relay or putting a toggle switch in to deactivate the system as wanted.

 

well damn Mel, that just doesnt seem right(not saying it isnt so) I guess Im happy that I have the 2wd option then.

 

Just to state it another way - when in A4WD the front wheels are not receiving any power (even though the front hubs, axles, differential, front driveshaft, etc. are spinning). But when wheel slip is detected the transfer case clutch is engaged automatically and transfers power to the front wheels. (Placing the selector switch in 2WD (if you vehicle has that option) or pulling the fuse keeps this automatic engagement from taking place.)

(If you place the selector switch in 4H or 4L, the transfer case clutch stays engaged until you move the selector to another position.)

Personally, I wish my Navi had the 2WD switch position. One windy night last winter, running Route 5 along Lake Erie between Buffalo and Erie, Pa, the roads were bare. Came to a left hand curve and just as I approached the apex, suddenly there was about 8 inches of wind driven snow accros the curve. I felt the back end start to lose traction and as I started to steer slightly right to correct for the back end coming out, suddenly, wham!, bang!, the transfer clutch engaged powering the front wheels and it just wanted to go straight off the right side of the road. Got it gathered up before all four wheels were off the road. Took an old timer like me a few seconds to realize you can't steer it with the throttle around a curve when it is in 4-wheel drive. You gotta get out of the gas to transfer more weight up to the front so you can steer with the front wheels.

Sorry for being so long winded, but maybe my experience will help the young 'uns............

 

And that's a fact. Thanks for reminding me of it and for that reason alone I'm going to put a toggle switch in the fused line so I can have the 2WD option on my Navigator without going under the hood to pull the fuse. I peronally like to hang the tail out once in a while as well as do a little 4 wheel drifting, but only when I am in control of my vehicle. Ford's version of A4WD has taken that away from us and as PDQ said, the A4WD can and will come in at perhaps the worst possible moment putting you into a ditch, a guardrail or worse.
Somewhere in this thread is, I think, a post showing the wire to put the switch in. That will be one of my projects this weekend.

 

Can anyone confirm that is is fuse 104?

 

YEP! (all the way at the end of one row of the block under the hood). I took ours out and sharpie'd 104 on it. Made a huge difference for us at least because the AWD unit kept sensing slip on gravel/wet pavement and trying to engage. Hated that. And did see a big difference in steering feel as well as a 2mpg difference. But ours was truly trying to engage when it shouldn't have. Hate having hubs that are always locked. Turning all that gear is great for lubrication when you do need it...at the expense of everything else.

I don't have the rig anymore, but this was on our 99. Got an email notification and felt obligated to reply.

 

Thank you for the quick reply. I am going to go try it now.

 

Good luck with it...and grab some needle nose! Will need to get that sucker out of there!