No, there is an auto position (counter-clockwise) and a lock position (clockwise). Leave them in auto all the time. When you turn the **** on the dash a vacuum pulse is sent to the hubs and they should (when operating correctly) lock on their own. When you turn back to 2wd another pulse is sent and they are supposed to unlock. The lock position is there to manually lock the hubs should the auto system fail either at the vacuum end or the hub end. Lock will always get you in 4wd if the auto position does not work. Put your hubs in the counter clockwise Auto position and consider lock to be only Plan B. If everything works correctly you don't have to leave the drier's seat.

 

Which is OK but everything will be spinning up front all the time which is OK but will affect your gas mileage. I leave mine locked all winter just because the auto part doesn't always work perfectly and it it still just a matter of flipping a a switch. I don't think Chevy has that feature.

 

Not in auto with the switch off......freewheeling then

 

Yeah, but Brent's post was a comment directed solely at the aforementioned "plan B."

Stewart

 

Ok. So the Mile Marker 449ss will work the same as the OEM's currently? Is that an easy fix?

 

With OEM vacuum operated hubs installed:
- some of the OEM hubs are not marked with "auto" and "lock". In this case, only punch mark size divits are present on the outer ring of the hub.
- As Skinsfan6, (Go Steelers!), posted ealier, "auto" is selected when the center of the hub is turned couter-clockwise; "lock" is selected when the center of the hub is turned clockwise, (or as Festus on Gunsmoke would say, "Contrary-clockerwise" and "Clockerwise").
- In "auto", the front axle is free wheeling. When four wheel drive is selected on the console inside the truck, a vacuum is used to engage the hub and front axle. The transfer case gearing is electrically, (no vacuum used), locked up at this time to the front propeller shaft.
- In "lock", the front hub and front axle are engaged, however, the transfer case is not locked up and the truck is not in four wheel drive until the driver selects that position on the console switch inside the truck.

The Ford OEM vacuum operated ESOF system I have found problematic in three areas:
- the vacuum lines from the reservoir, (located inside the engine compartment on top of the passenger side fender, next to the small vacuum pump), to the wheels are plastic and can break or leak anywhere along their run; especially near the wheel. Some drivers have replaced the run inside the wheel well with braided steel lines in an effort to protect them from road hazards.
- over time, the hubs themselves become corroded or dirty causing them to be difficult to manipulate, and often impossible to move.
- the center of the hub that is turned to select "auto" or "lock" is made of plastic, which if cracked, will not allow for a proper vacuum for "auto" hub engagement , ((which is what WILL happen if a pair of channel locks is used to routinely move the selector. I know... I should have taken pictures)). This plastic center portion is very susceptible to damage from trail hazards such as rocks. Vacuum seals inside the hub may also fail, causing a loss of vacuum.

"Sgt Smith Productions" has a very good tutorial video available free on YouTube which demonstrates how to remove and lubricate the OEM auto hubs.
Ford Super Duty Lubricating a 4wd locking hub Part 1 - YouTube

Guzzle also has a pictorial tutorial on his garage web site. Replacement "O" rings and seals can also be purchased from him.
Welcome to guzzle's 4x4 Autolock Hub Lubrication Maintenance Web Page

These hubs cost $500 a pair at the dealer, however, they can inexpensively be replaced with very reliable Mile Marker or Warn manually locking hubs. As has been posted else ware on this forum, a pair of Mile Marker 449 SS hubs is currently on sale at Summit Racing for $89.50, plus shipping.
Mile Marker 449SS - Mile Marker Supreme Locking Hubs - Overview - SummitRacing.com

One last recommendation:
If you are able to freely manipulate the OEM hubs from "auto" to "lock", the truck may still NOT go into four wheel drive with the hub in the "auto" position even with the transfer case locked by selecting four wheel operation on the console, and the "4x4" advisory light illuminated on the dash. This condition is more than likely caused by a vacuum leak either along the vacuum lines running from the pump to the hub, or a vacuum leak in either of the hubs themselves. I would advise that next time you have a little free time, ensure the OEM hub is in the "auto" position, select four wheel drive on the console inside the truck, and turn the steering wheel all the way left or right to the stop, then VERY slowly move the truck forward. You should get the tell tale "binding" and bouncing of the steering wheel indicating that the front axle is indeed locked and receiving power from the transfer case via the front drive shaft. If the front axle does not bind under this condition, then the front hubs are not locked indicating a failure of the ESOF system. Four wheel drive, however, can still be achieved by manually moving the hub to the "lock" position.

If the OEM hub is manipulated frequently, (once a month or so), and every so often, removed, cleaned, and regreased, it should provide years of service. More frequent servicing may be required if the truck is exposed to mud, water, and winter driving conditions. However, vacuum leaks in the system, either in the lines or the hubs, may be difficult to run down. If the ESOF system is inoperative, but the OEM hubs freely move from “auto” to “lock”, replacing them with manually locking hubs seems redundant to me, as well as a waste of money. Simply keep the OEM hubs and know that the “auto” mode is inoperative. If the OEM hubs are stuck or binding, even after they have been serviced, an aftermarket install of a quality manual locking hub may provide the least amount of inconvenience and expense.

There are certain design engineers that I would like to meet some day. The one who designed this Ford vacuum four wheel drive system with plastic hubs is one of them.

 

SO the button on the inside engages the the front axle and it sends a signal to the vacuum pump to engage the hubs right? So if the axle engages but the vacuum has leaks then you can get out and lock the hubs manually and still have 4-wheel drive, correct?

Sorry, I am just trying to understand this because like I said I have never had a vehicle with this setup. In my Dodge I just shift the floor shifter and 4-wheel I go!

 

Yep that's it....You got it

 

Don't be sorry. You will not find a lack of people, like me, on this forum who simply live to tell other people how much we think we know.

Your statement is almost correct.

When you select 4x4 with the selector on the console inside the truck:
If there is a vacuum leak, the front axle will never engage if in "auto".
If there is a vacuum leak, the transfer case will engage.
If there is a vacuum leak, you can still engage the front axle by getting out and locking the hubs manually.

I also liked the four wheel drive stick in the floor, and manual hubs on my 1975 Ford Bronco, and 1988 F150. My 1999 Suburban's front axle is locked by an electric motor in the axle. I had my doubts about it, but it has worked flawlessly for over 12 years. I have seen Dodge trucks, which came stock with the front axle always spinning, whether in 2wd or 4wd, that had aftermarket electric motors and manual hubs installed on the front axle so that it wasn't always engaged.

 

Sorry, I meant the transfer case and not the axle. So the vacuum pump has nothing to do with the transfer case and front drive shaft, right? The vacuum pump is only engaging the axle and if there is a leak it will not.

I think I got it.

 

I should have re-emphasized the fact that the driver may think the truck is four wheel drive, when in fact it is not.

With the hubs in "auto", and the driver selects four wheel drive inside, the transfer case will lock up in 4hi or 4low. The "4x4" indicator light will illuminate on the instrument cluster. All the indications of being in four wheel drive are present, however, if there is a vacuum leak, the front hubs will not engaged.

The only way I know how to tell if the ESOF system is working properly is to turn the steering wheel all the way, and feel the binding in the front steering. Otherwise, the driver may see the "4x4" light and think the truck is in four wheel drive, when in reality, it is not.

ESOF. What a system

 

Correctamoondo. The vacuume is only used to engage the hubs. If you look at the pictures I linked earlier, you will see the little rubber flapper seals buried inside the auto hub.

If you look behind the wheel in the fender well, you will see the plastic vacuum line going into the wheel hub. This is a very vulnerable spot for the plastic line.

 

I got to thinking about vacuum leaks and remembered that the air conditioning and heating vents inside the cabin are run off of vacuum, as well. If there is a large enough vacuum leak, the vent position defaults to defrost. I guess if you cannot direct the cabin air anywhere other than defrost, regardless of switch position, it might be a very good indication that the OEM hubs will not automatically lock either.

 

If my auto locking hubs are working correctly will they physically move from auto to manual or is it all internal. I noticed that when I use the switch inside the cab it feels like they engage but it's not the same as manually locking the hubs.
It seems like manually locking the hubs is true 4wd

Wopr21

 

If the auto hubs are working correctly, the only movement that takes place is inside the hub. The selector which in on the outside does not rotate from "auto" to "lock".

If the auto hubs are working correctly, there will be no difference in the truck's four wheel drive response between automatically locking the hubs, or manually locking the hubs.

If you have doubts as to whether the hubs are automatically engaging with the hubs in the "auto" position when four wheel drive is selected from inside the truck, a sure indication is the "bucking" and "binding" that occurs when the steering wheel is turned all the way to the stop in one direction, while SLOWLY moving forward.