i just bought an 01 f250 with the 7.3. And i really dont know much about it. It doesnt have an owners manual, so i was going by what the guy told me on how to engage the 4h.
We got some snow/sleet/ice and i wanted to go down the street and see if the 4wd works. The guy told me you can put it in 4h anytime while driving as long as no wheel is spinning. I put it in 4h before i left and its just the 2 back tires spinning. Tried moving the switch back to 2wd the to 4h again and the same thing. Am i doing something wrong or is there something wrong with the truck?

 

If it's not doing anything when you flip the switch it might be a vacuum leak preventing the hubs from locking in. You should be able to manually lock the hubs in by turning the black dial (hub lockout) on each of the front tires. They are typically set to "automatic" but give you the option to manually lock them in for cases just like this. After that, flip the switch and see what it does. My Excursion just started doing the same same thing. I had to manually lock in the hubs, and it's been fine since.

 

so you can turn the levers on the front hubs and it will work in both 4h and 4L?
i know absolutely nothing about these.

 

ESOF(electronic shift on the fly)
2H: front hubs are unlocked(able to move independently of front axle) transfer case is in 2h(no power to front driveshaft, power to rear driveshaft)

4H: when you engage the switch into 4h it sends vacuum to the hubs on the front whells, which locks them to the axle, the transfer case then changes to 4x4(powers both front and rear driveshaft)

4L: same as 4H with the addition of engaging a reduction gear in the transfer case

if the front hubs are not engaging, the drive front axle will be spinning, but no power will be transfered to the wheels. if the hubs are manually locked in, all 4x4 should work fine.

you can run in 2H with the front wheels locked(puts slightly more wear on front end, and decreases milage a little bit due to additional rotating mass) lots of people will lock their front hubs for the entire winter.

 

im curious as to if the 4wd even works.
If i wanted to check it, are you saying i can manually switch the hubs and then put the switch on 4h and see if its working? And if i do that, does it matter when you move the switch on the dash, meaning in park, neutral, moving, etc?

 

shouldn't matter when you move the switch, but can take several seconds for the 4x4 to engage

 

Go look at the hubs on the front of your truck thay should say auto and locked
turn the black *** to lock then try it. As others have said it be a vacume leak with the auto part of your hubs.

 

went and did a little test on the snow/ice.
first of all, the hubs dont say anything or i couldnt find anything on them, so i turned them both clockwise about a quarter of a turn...got in and put the switch on 4h and went out and im guessing its working, because before where the back end would just spin and try to fishtail, now it just seems to take off. So the 4wd works right, there is just an issue somewhere else?
And is it ok to drive it with the hubs locked like that and in 4h? Like at 50mph or so?

 

Correct. You can shift into 4 High anytime you want - in park, neutral or moving (though I personally woudn't engage it moving faster than 20-30mph). To shift into 4 Low however you need to be completely stopped and in park or neutral.

 

Sounds like the transfer case is engaging so it's just your hubs - like others have said it's probably a vacuum leak. Do a search on here there's tons of posts about tracking it down or replacing the hubs. And yes, it's fine to leave them locked in and drive 50mph. I think the manual says you can go up to 60-65 in 4high?

BTW, you can download a manual for free at www.flmowner.com

 

when you tried to engage the 4x4 before did your a/c change to the defrost vents?