How does the 4wd engage on an F350

[James86004]

I was driving one of work's F350s up the mountain yesterday, and had a minor issue getting it into 4wd Hi. I think this is a 2000 or 2001 model. It has automatic hubs on the front, and an electrical switch on the dash for controlling the 4wd. I got to an icy portion of the road, and could not climb it in 2wd. I thought all I had to do was switch it to 4wd, and 4wd and the auto hubs would engage. I did this, but in the several seconds I gave it gas, I heard the engine speed up and felt the rear of the pickup slide sideways. I then got out and manually locked the hubs. Again, the engine sped up, the rear slid sideways, but after a couple of seconds something engaged and I was able to make easy forward progress.

How does the transfer case work on these? Is it normal for it to take several seconds to engage? Do the auto hubs also take a while?

Thanks,

James

 

[akfj40]

once your hubs are locked in it will be in 4wd as soon as you switch it to
4wd. if you have a dial on the dash, you have vacuum actuated hubs, in therory the will go from free spin to locked if they are not already locked in. sometimes the vac motor dont work or the lines get leaks and that sounds like what happen to you. if everything works and there are no leaks it can take a few rotations on the front wheels to engage from free to lock then be in 4wd. does that help?

 

[Martinjmpr]

I have been very surprised to see Super Duty Fords and the Excursion with what appear to be manual hubs. I don't know why you would combine a push-button T-case with manual hubs but it does appear that Ford did so for reasons I suppose they understand.

Your narrative seems to answer its own question: You weren't in 4wd until you locked the hubs manually. I have never seen a manual hub that was also an automatic hub, except for some of the really, really old "automatic" hubs sold by Warn, I think. IIRC those had two positions, an "automatic" setting and a manually locked setting. In the manually locked setting they were locked just like regular locking hubs.

In the automatic setting, they would lock when power was applied to the front wheels and unlock as soon as there was no power. From what I recall the problem with these was that if you were going up or down a hill slowly they would unlock every time you took your foot off the gas and if you were descending a hill on compression only (i.e. not on the throttle) your front end would be unlocked.

Of course, this is all 2nd hand info because I never had these kinds of hubs myself. My only vehicle with "automatic" hubs was my 1990 Montero which had hubs that would lock when you shifted into 4wd and remain locked even after you shifted into 2wd, until you backed up about 5'.

 

[James86004]

once your hubs are locked in it will be in 4wd as soon as you switch it to
4wd. if you have a dial on the dash, you have vacuum actuated hubs, in therory the will go from free spin to locked if they are not already locked in. sometimes the vac motor dont work or the lines get leaks and that sounds like what happen to you. if everything works and there are no leaks it can take a few rotations on the front wheels to engage from free to lock then be in 4wd. does that help?

Sounds like I need to confirm the vacuum lines are good. It was a little hard to tell on the downhill part if I was in 4wd or not.

Your narrative seems to answer its own question: You weren't in 4wd until you locked the hubs manually.

I am not sure if me locking the hubs manually was what did it, or if I just didn't spin the wheels long enough the first time to get it in 4wd.

In the automatic setting, they would lock when power was applied to the front wheels and unlock as soon as there was no power. From what I recall the problem with these was that if you were going up or down a hill slowly they would unlock every time you took your foot off the gas and if you were descending a hill on compression only (i.e. not on the throttle) your front end would be unlocked.

Yikes! The hubs look just like the manual hubs on our F250, except they are labelled "Lock" and "Auto". I think I will put them in "Lock" next time.

Which brings up another question. If you have a limited slip diff in the front, is there any problem with leaving the hubs in "Lock" while you are in 2wd? Someone told me it was bad for the LSD to backdrive it like that.

 

[marke]

Hi, I have a 2001 F250 with the electronic 4WD select. It does have automatic locking hubs and it does use vacuum as AKFJ40 mentions. If the rubber line is cracked (which happens often) the hubs won't lock up, hence the reason for have a manual mode. It does take a while for the system to go into 4WD but not as long as it seems it took for you. I haven't had any troubles with that. Also, I haven't had any troubles with the hubs unlocking on my way down hills. That would be scray! Just my 2 cents. Mark

 

[Carlyle]

Marke is right on the money there. One thing to note is it always easier on the whole system to come to a complete stop, no spinning wheels, before engaging the 4wd "on the fly".

 

[James86004]

Oh, the HUBs are vacuum operated. Ah-ha! I never would have thought of that. I thought you meant the transfer case actuation.

 

[masterplumber]

Another problem I've seen just to be aware of... with all these vacume controled gizmos all tied together a company I used to work for had a fleet of Chevy S10s that a bunch of them developed a leak in the vacume motor on the transfer case switch & sucked ATF into the entire vacume system causing all kinds of havoc.

Doug

 

[MattScott]

our excursion we used to own had this same problem, it was a 2000. The vaccum system freezes up. you have to engage the 4wd from the cab, then go out and lock the hubs, at least ford gave a backup.

 

[jdholder]

I have changed out my Ford "Automatic" hubs for a nice set of Warn Manual Hubs. I just feel better knowing when the hubs are locked and when they are not.

 

[locrwln]

Part of the reason when I bought my truck, I made sure it had the manual hubs and manual t-case lever. I know when it's in 4wd and when it's not. I can lock the hubs if the weather might be bad and it has very little effect on the driveability or mileage, when I need 4wd, it is a matter of reaching down and pulling the lever back. With the hubs locked, it is shift-on-the-fly.

Jack

 

[Carlyle]

I have changed out my Ford "Automatic" hubs for a nice set of Warn Manual Hubs. I just feel better knowing when the hubs are locked and when they are not.

Probably a really good idea for all us Ford owners.

 

[akfj40]

all "auto " is, is an option to engage from the cab, it really is nothing more than "free" forget going with the hubs, they are not any more stout than factory. your weak point on the front end is the unit bearings. big tires and water or mud crossing is hell on them, non servicable and expensive. heres another option to go to the old school, but tried and true setup.
http://www.dynatrac.com/products_0507freespin.html

 

[Sportsman Matt]

My Ex- wife's father had the same problem with the hubs not engaging when in automatic mode on his excursion. He took it back to Ford twice and they replaced them with the same automatic style hubs the first time and then just manual locking hubs the second time. Reason for the second time was even the techs at Ford couldn't figure out why they wouldn't engage, so the resolution to make him happy was to put in manual lockers. Never had a problem after that.

 

[James86004]

Thanks for all the responses. I would just assume leave the hubs locked all winter. Are there any problems with doing that?