I've read a few posts and honestly, I don't get it. So, I'm going to ask the question (the only dumb questions is the one not asked - or searched for).

I have ESOF. So that means I can use that to go into 4x4. My hubs are set to "AUTO". Now, from what I've read, sometimes it may not go into 4x4, and some people here don't trust the vacuum.

I've read that ESOF you can leave it to locked on the hub, but it won't be in 4x4 until I turn the swtich in the cab? I may give up a bit of mpg leaving it like this, but at least when I put it into 4x4, it will make sure it goes in.

Right?

But my I thought if I switched it to "locked" it would lock it into 4x4, and then I wouldn't need the switch in the cab. Am I wrong on thinking this? Will it not be "4x4" when set to locked until I do the switch?


Hubs set to Auto and using the switch = it may not always work.

Hubs set to Lock and using the swtich = always works
(more wear and tear, and less mpg)

 

When you turn the ESOF switch on the dash to 4x4, it does two things, one is to send a vacuum signal to the hubs to engage, the other is to send an electric signal to the transfercase to shift into 4 wheel drive.

If you put your hubs in the lock position but leave the dash switch in the 2 wheel drive position, the front axles and gears will be spinning but the transfercase is not engaged. So you will not be in 4 wheel drive until you turn the dash switch to 4wd high or 4wd low.

 

Yes, if you put your hubs in the LOCK position and just use your ESOF selector to control your transfer case it would work OK. You will use a little more fuel, you'll hear a little more noise (front axle, differential and driveshaft will be spinning) but it won't hurt anything.

It SHOULD always work with your hubs in AUTO, but the system is at best problematic. This is what the conversion to a manual hub uis a popular modification. Also, the aftermarket hubs are stronger than the Ford hubs and a whole bunch less expensive.

 

I don't understand what gets converted to manual hubs? I know that you change the hubs out to something like WARN Hubs, and plug the vacuum line.

But I don't understand what's after that, or why you would want to do that if you can put it in lock and then use ESOF? Wouldn't it do the same thing? If you use manual hubs, you need to to set them to lock. Then what?

Maybe that's what's confusing me....

Also, if you use manual, and you are set to lock, wouldn't you be in 4x4 all the time until you set to auto/off to the hub?

 

With manual hubs, you turn them to FREE when you're not using 4 wheel drive. That way you don't have to spin the front axle, differential and driveshaft. It creates less drag to save a little fuel and cuts down on noise a bit.

4 wheel drive systems have two controls. First, you have something controlling the transfer case. You shift the transfer case from 2H to 4H, it sends engine power to the front axles via the front driveshaft and front differential. You can also shift to 4L, which reduces your gearing to all axles. On my truck this transfer case is controlled by a floor mounted lever.

Second, the hubs are locked or unlocked. If unlocked, the wheels spin freely from the axles. If locked, they spin with the axles.

The ESOF system combines the two controls into one dash mounted switch.

The ESOF system has two very weak points. First, the automatic hubs aren't real good. They can leak, fail, seize or just be balky. This is why you have a setting to bypass the automatic function of the hubs, just lock the hubs to the axle.

Second, the motor that shifts your transfer case can fail, leaving you unable to shift into 4H or 4L, or worse shift out of 4H or 4L. No one has come up with a solution for this problem, yet.

A third component that often fails is the vacuum solenoid, which is what sends the vacuum signal to the hubs for locking and unlocking.

 

Another difference between the factory auto hubs and aftermarket locking hubs is that the auto hubs won't unlock if you have a vacuum leak.

Both style hubs work the same when they are in the lock position but when you turn the auto hubs to "auto" they won't unlock until they have the proper vacuum signal which means if you have a vacuum leak they will stay locked.
Manual hubs will unlock as soon as you turn them to "free".

 

It is always a good idea to set the hubs to "lock" on a monthly basis to keep everything lubed up and working well. Wether you have ESOF or manual hubs. The electric switch on the transfer case can malfunction too. You may not have 4 wheel drive even if the hubs are locked and the switch is in 4X4 mode.

 

GregsSD,

I have never heard that before. Are you sure? I am quite certain that I have the vacuum leak. Ive just been using the switch to engage the transfer case and will turn the **** from auto to lock before I get into any situation where i may need 4wd. If what you are saying is true then my hubs are locked all the time? Please tell me this isnt true.

Bob

 

Is there some way to test and see if my hubs are locked when the **** is in auto?

 

Reach under the front end of your truck and see if you can turn each drive axle by hand. Each one should turn without too much force. If you can turn them, the hubs are unlocked. If you cannot turn one, that hub is locked.

 

Here is the info from the TSB section about autolocking hubs:



<TABLE><TBODY><TR><TD>This publication contains material that is reproduced and distributed under a license from Ford Motor Company. No further reproduction or distribution of the Ford Motor Company material is allowed without the express written permission of Ford Motor Company.


TSB Main Page
<TABLE cellSpacing=0 cellPadding=3 width="96%" border=3><TBODY><TR><TD bgColor=#0000ff colSpan=2></TD></TR><TR><TD class=VERTCENT align=middle width="25%" bgColor=#ffffff>TSB
03-4-1
</TD><TD class=VERTCENT align=left width="65%" bgColor=#ffffff>

• FRONT LOCKING HUBS - SERVICE TIP

</TD></TR><TR><TD bgColor=#0000ff colSpan=2>Publication Date: February 14, 2003</TD></TR></TBODY></TABLE>
<TABLE border=0><TBODY><TR><TD width=230>FORD:
</TD><TD>1999-2003 SUPER DUTY F SERIES
2000-2003 EXCURSION</TD></TR></TBODY></TABLE>



Article 00-8-6 is being republished in its entirety to update the model year coverage. ISSUE:

This TSB provides information on the 4X4 system, particularly the front locking hubs.

ACTION:

Refer to the following text for information regarding the 4X4 system and the front wheel hub locks.

SERVICE PROCEDURE



4X4 ESOF LOCKING HUB: DIAGNOSTIC AND SERVICE ISSUES





Many system components are involved in proper operation of the ESOF (Electronic Shift-On-The-Fly) locking hubs on 1999 and newer Super Duty and Excursion 4X4 vehicles. Before diagnosing the hub locks themselves as the cause of 4X4 concerns, be sure to verify all related system components. HUB LOCK OPERATION





The Super Duty and Excursion 4X4 ESOF system uses timed vacuum sequences to lock and unlock the wheel ends. A high vacuum level is used to engage the hub locks, and a lower vacuum level is used to disengage the hub locks, after which the vacuum is released and the hub lock holds itself in the proper mode. The vacuum signals are supplied to the hub locks by system components, including Generic Electronic Module (GEM), wiring harness, solenoid, vacuum harness, and vacuum seals. As a first step in service, eliminate such obvious items as loose wiring connections, loose vacuum connections, or damaged vacuum lines. DISENGAGE TIME





"Slow" release of the hub locks is not considered abnormal for this system. Anytime vacuum is applied to the hubs, whether for 4X4 or 4X2, the hub locks will initially engage. If 4X4 was requested, they will remain engaged, but if 4X2 was selected, the internal mechanism will release only after the GEM timers expire and vacuum is vented from the hub. This normally takes 15 seconds, but can take up to 2 minutes depending on how the 4X4 mode switch was operated. After the hub mechanism releases, internal springs must work the hub lock gears to the disengaged position. Road bumps, vehicle speed, acceleration cycles, or momentary reversal of direction can assist this process, varying the length of time the hub locks remain engaged in each situation. MANUAL OVERRIDE

The hub locks have manual override selector dials which, when rotated to the "lock" position, will keep the mechanism locked regardless of the instrument panel 4X4 mode switch position. Verify that both dials are in "auto" before evaluating ESOF operation.

</TD></TR></TBODY></TABLE>

 

If I go with Warn Hubs, and plug the vacuum line, will I still need to use the switch in the cab to engage the transfer case - right?

Since the hubs would already be locked by me turning them to "locked", the switch would only be used to send power to the transfer case. Then if I switch back, it will dis-engage the diff, but the hubs will still be locked (though not in 4x4) until I use the switch again.

Now what happens if I get manual hubs, block off the vacuum line, but leave the hubs to auto/off. Then use the switch to 4x4.... it would not go into 4x4 because the vacuum line would be blocked off and it would only spin the transfer case.... right?

Sorry for the dump question. I'm trying to learn.
I know PC's. Not cars - yet.

 

OK, if you get manual hubs there is not an AUTO position on the hubs. The hubs are either LOCKED or FREE.

If they had an AUTO position they would be automatic hubs, not manual hubs.

Yes, the switch will still control the transfer case if you install manual hubs.

 

Yes, if you switch out to manual hubs you will still have to use the switch on the dash to shift the transfer case into 4x4.

All the hubs do is create a connection between the front wheels and the front axle. If the hubs are in the free, or auto position (and the vacuum pulse hasn't been set) the hubs are not connected to the axle, and can turn independantly from it. If you trun the hubs to the lock position (or send the vacuum pulse to tell them to lock) then the hub engages and a pysical connection between the wheel and axle is made. This forces the wheel and axle to rotate at the same speed whether or not the transfer case is engaged.

The transfer case controls the connection between the engine/transmission and the front and rear driveshafts. If the transfer case is in 2wd, the front driveshaft is not connected to the engine/transmission and can turn freely. If the transfer case is shifted into 4x4 high, a physical connection between the engine/transmission and front driveshaft is made allowing the engine to power the front axles.

So a quick breakdown would be.

Front hubs locked, transfer case in 4wd, power to the front wheels. This is a working 4wd setup.

Front hubs locked, tranfer case in 2wd, the axles and driveshaft will turn with the wheels but there is no connection to the engine, so no power is transferred to the wheels. You can drive around like this but it does cause a small increase in wear on front brakes, axle bearings, and u-joints. This would happen if the electric transfer case motor failed to engage the transfer case, the 4x4 light on the dash would not light up. This would also happen if the auto hubs failed to disengage on shifting back to 2wd from 4wd.

Front hubs unlocked, transfer case in 4wd, the engine will be powering the front driveshaft and axle, but since the hubs are unlocked no power will be transferred to the wheels. This is the most common failure of the ESOF system with the auto hubs failing to engage. The 4x4 light on the dash will light up, but you will have no power.

Front hubs unlocked, transfer case in 2wd. This is normal 2wd situation where the majority of the driving takes place.

 

One more advantage to switching to manual hubs is that you can leave the hubs unlocked and switch the transfercase to 4wd-low range. This will give you low range but only for the rear wheels which can be helpful if you are moving a large trailer around in tight spaces.