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shift-on-the-fly 4x4 operational help


Old 07-23-2004, 09:25 AM
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Join Date: Nov 2001
Posts: 9
shift-on-the-fly 4x4 operational help

I have a 99 F250 superduty 4x4 with shift-on-the-fly. This past weekend
I got stuck while in 2 wheel drive. I didn't have much room to manuvuer
front to back, maybe 6 feet. I flipped the switch and the 4x4 light
iluminated on my dash. Long story short, after an hour of sweating and
digging and wondering why the hell I was stuck because my front axle
should easily move me out of my jam, I manually locked my hubs. I put it
in reverse and rocketed out and almost took out my fence. I hadn't really
noticed but the front wheels were never spinning, I was in 2 wheel drive
all along.

This is my first time stuck and have only used 4x4 for winter driving.
Do I have a problem with the O-rings loosing vacuum or is there some
minumum distance the wheel must travel before the shift-on-the-fly will
engage the front axle?

I know I could just go back out and try it on a dirt road to see if my front
wheels will engage, and I will, but I would like to hear some thoughts.

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Old 07-23-2004, 09:51 AM
Join Date: Nov 2003
Location: Baltimore, Maryland
Posts: 31
if you had to get out and manually lock the hubs that was your problem...even tho you have "shift on the fly" or the turn **** for need to lock the hubs to engage the front wheels. now my guess is that when you put it in 4x4 the frotn axle was spinning but with the hubs unlocked it did not spin the wheels. manual locking hubs are jsut that...manual, you must get out and turn the know to lock them in for the front wheels to receive power formt he axle

the only time it is true "shift on the fly" 4x4 is when you have auto locking hubs that engage by them selves. but unless you lock the hubs before getting dont ahve a true "shift on the fly"

if anyone thinks im wrong please let me know
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Old 07-23-2004, 09:56 AM
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Join Date: Nov 2001
Posts: 9
I have auto hubs, but there are two positions they can be in, "auto" and "lock". I have never had to move them from "auto" until now. I imagine the "lock" position is exactly for my purpose, if the shift on the fly fails to lock your hubs via the vacuum system then you can get out of the truck and lock them yourself. I am curious if there some minimum distance the wheel must travel for the automatic vacuum system to engage or if my O-rings have a leak.

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Old 07-23-2004, 10:26 AM
Join Date: Nov 2003
Location: Baltimore, Maryland
Posts: 31
wow i didnt know they had those kind. thanks for educating me...have you ever ahd the front hubs off to replace rotors or a u-joint..if so the hubs could be ruined now...happened to my explorer...took the hub off to replace rotors and then they would never work so i replaced them with Warn manual locking hubs at $400+labor being i was 7 hours from home when i got stuck and had no tools to do it myself
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Old 07-23-2004, 11:06 AM
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Join Date: Nov 2001
Posts: 9
The superduties have this "safety feature" on the hubs. IE the ability to move them from auto to lock. Don't know about the light duty F-series, though. Anyway, I did have the rotors done back in March (for the first time). In fact the guy had to do them twice since he screwed up the first time. So the front hubs were off the truck twice recently. I duess I will grab the wife, go to a dirt road and floor it and check for front wheel spin.

Thanks for the tip.
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Old 07-24-2004, 01:02 AM
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Join Date: May 2002
Location: WV
Posts: 161
On Superduties with electronic-shift-on-fly two things normally happen when you switch the thing to 4x4.

1. The transfer case engages so the front axle gets power.
2. The hubs automatically lock and engage the front wheels.

Both of those things have to happen before your front wheels will get power. It sounds like your vacuum-activated front front hubs did not work automatically. Luckily SDs have manually-lockable front hubs so you can switch them in manually.

The hubs switches have two positions. In "AUTO" the hubs lock in and out as switch the dash dial to 4x4 or 4x2. In "LOCK" the hubs stay locked in even when the dash control is turned to 2wd.

As far as whether or not the truck has to be rolling to get into 4wd, I'm not sure. I've heard alot of guys who hate ESOF say this is true and that's why they like a full manual 4x4 system but my F250 is electronic 4x4 and mine engages sitting still all the time. At least with Ford's esof system the hubs can still be turned in manually even if the vacuum switch fails so it's about the most reliable on the market now.

I had a good talk to a Jeep salesman a few weeks ago and he told me Jeep will only use a manual transfer case lever because they want to build the most foolproof 4x4 system on the market and the dash switches are prone to failure. Jeep won't use this cheap stuff because folks who buy Jeeps expect them to have the most reliable stuff blah, blah, blah.

I asked him what happens when the auto-engage hubs on a Jeep fail to lock the front axle. He shook his head & said "It won't matter because the lever that "hooks-up" The transfer case can't fail."! Typical-he had no idea. I don't know about you guys but I don't remember seeing any manual hubs on Jeep Liberties and those $50K Grand Cherokees!!
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