ESOF problems on two trucks--possibly related
 

Ok, here's what I've got:

2003 F-350 CC DRW. ESOF will not engage the 4x4 unless the hubs are manually locked first. When I flip to 4x4, it can sometimes take up to a minute to engage, even when rolling forward. Sometimes, if I'm not moving at all, it won't engage at all, but not always.

From what I hear, there are two probable causes for that: vacuum pump, and solenoid. The normal test for the vacuum pump is to see if the air will ONLY come from the defrost. Here's the kicker... sometimes it does, sometimes it doesn't. It's not consistent. Is it possible for a vacuum pump to sometimes work, or is it just a straight "yes it works" and then "no it doesn't?" Sometimes (but only while I'm driving in 4x4) the air will move back and forth while I'm driving from defrost/feet to just defrost.

Second truck/problem: 2006 F-250 CC SRW. ESOF will not engage the 4x4 unless the hubs are manually locked first. When I flip to 4x4 and I'm NOT moving, it can sometimes refuse to change period. Even to 4x4 Low. Had it happen twice, both times when I was stuck and couldn't move. In addition, when I go back to 2x4 with the ESOF switch, the front left wheel doesn't release unless I put the truck in reverse and roll backwards at least 5 feet. If I drive in 4x4 or in 2x4 without backing up first, I get a loud vibration/grinding sound out of the left front wheel at any speed over 25-30, getting louder and worse the faster I go.

I'm thinking this truck may have two different problems--either a vacuum pump or solenoid problem, AND a problem within the hub on the front left. I've never had any issues with my airflow in the cab, though, so I'm thinking the vacuum pump is okay. Strangely enough, the problem with the front left hub sticking happened when my shop put new tires on the front. Never happened until I drove away with the new tires, and happened that day. Has never NOT happened since. The shop swears that nothing they did could have caused that and wants to charge me to fix it.

Thoughts on either or both problems? Neither truck will go into 4x4 EVER with the hubs set to automatic, which sucks cause I've got some really tight turns on my property and having the hubs manually locked makes my turning radius awful.

Thanks!

unhook a vac line at the pump and see if it runs.
so far as the grinding / ratcheting sound goes suspect faild hub or axle

all i kno is i had problems with mine and there are 2 relays on the drivers side i think under a black box mine were really rotted bad chkk that out i was surprised hope that helps .

If I'm reading this right, your problem is that you are trying to engage 4x4 while not in motion. With ESOF, you need to be moving for the hubs to lock in. That's why Ford put the manual levers on the hubs as well, so that if you need to engage 4x4 at a stand still to get out of trouble and can't roll the wheels you can still get the hubs to lock by manually locking them. With ESOF, the wheels need to be turning for the hubs to auto-lock.

I see that you are also having issues engaging while in motion and Cheezit and the guys will set you straight on that one I'm sure. But I figured I'd better chime in on the failure when not in motion, as that is normal.

Not true, when my hubs worked, I could shift in 4X4 high or 4X4 low when sitting still no problem. In my truck, in some cases, it took 30 sec+ or so to engage the 4X4 when moving. Now it engages ALL THE TIME (I installed manual lock hubs and plugged the vacuum line, case closed)

Hmmmm, guess I'll have to try that one again. In the past I have found that if I am sitting still on a hill and on ice, that if I shift into 4x4 high my rear tires will just spin. If I can roll back a few feet, the hubs will seemingly lock in where I then can drive up the hill with power to all four wheels. I had thought this meant the front wheels need to be turning to engage the hubs, but maybe something is wrong with MY truck.:-huh

Yeah, I've definitely been able to shift using the ESOF while at a stand still in the past...

Cheezit, can you elaborate on what you mean by failed hub or axle? That concerns me, as I'm guessing a failed axle wouldn't be cheap... and may not be covered by my after market warranty.

Okay guys, I did a search and found that my above comment was in fact true, according to the link I am posting here. Read it through and maybe some of you may benefit from the knowledge here. This link's information is what I had believed true and it seems some aren't aware of this.:-X22
Auto Hub use, maintenance, and modification - TheDieselGarage.com

Here's another one. Simpler explanation with pics

ESOF 4-Wheel Drive Operation

Notice that it states "If shifted to 4x4 HIGH ( 4WD HIGH) while at complete stop, 4x4 may not engage".

In the first link I posted, above (post # 8), there is also some good information on maintenance to perform to prevent problems as well. Though I haven't had problems with my ESOF, I will have to try this procedure as well while doing regular maintenance.

Thanks for the links! Apparently though it wasn't designed to work that way, it has for some... I guess that's one potential problem I don't have to worry about anymore! :)

Ya know, I had thought about changing to manual-only hubs back when I first bought my truck, mostly due to a lot of people having problems. I figured I'd make the change once my ESOF quit working, but it never did. I have to wonder how many folks did that modification because they THOUGHT the ESOF system quit working, when it was actually "operator error" from lack of understanding how it works?

I suppose that if I didn't know how the system worked, while at a dead stop, and engaged the 4x4 switch, and my back wheels began spinning while creeping along, then BAAAAM the hubs would lock in, I suppose I'd be pretty pissed off. Heck, in some cases damage may even have occurred to hubs and/or transfer case from doing just that. If true, and the operator would have know that they SHOULD have manually locked the hubs before stepping on the skinny peddle from a stuck/stopped position, maybe ESOF may not have gotten the rap that it has. Kind of like the bad rap the 6.0 got from lack of understanding, maybe?

In any case, I've found mine to work fine, up to date (knock on wood), and I use my 4x4 a lot in the winter living in the Sierras. But if they do fail (while using properly) I think I can always pull over and lock them manually so I see no reason to worry about it for now. If they ever prove me wrong and screw up, I'll consider the manual hub swap at that time. Fingers crossed...

This is what fixed mine with the symptoms you are describing

And yes it was intermittent, maybe I got lucky I just spent the 60 and hoped, and as soon as I replaced it it worked perfect.

this is not one of my symptoms , you may have other issuer going on. Here that is related to the first. Is fixable by yourself , I bought all the crap to repair mine including the knuckle seal tool, and just never got around to replacing the ball joint and seals,The brand new tires are hiding my worn ball joint problem

When you crawl under the truck behind your front tire, and stick your finger in the u-joint and can turn the shaft with your finger it's safe to say your hub, or your hub seal is done. (that is, after verifying that you are getting the necessary vacuum pulse from the ESOF solenoid) Mine was inconsistent, the annoying thing is one hub refused to disengage, therefore, spinning the spider gear in the front differential making a horrendous noise. I'm very happy with manual hubs, time to install, 1/2 hour, price form Superwinch, $125.

So haven't been able to tackle the F-350 yet... fixed the problem on the F-250, though. I wasn't able to buy 4 tires at once, so I've been replacing them one at a time... Finally got my tax return, which gave me enough money to tackle the problem in that front hub... took it into the shop to get them to diagnose it so I'd know exactly what to fix, and after working on it for a while, they told me it was due to having mismatched tire sizes (all the same tire, but not all the same age, so tread depth gave me about a 1" difference in tire size). Said on 4x4 vehicles all the tires have to be EXACTLY the same size, or that can happen... sure enough, got my last tire in and installed this morning, and the problem is gone. How crazy is that???

not crazy at all. iy more common then you think