Howdy I have a 99 F250 Super Duty 5.4L (just joined the forum last week) and doing some work on the truck. It has 140K miles on it. Today I was trying to get out of my yard in the wet grass and found out my 4WD is not working properly. The ESOF appears to work and the dash lights come on for 4x4 and Low Range, and the Low Range gears work, but the front wheels are not pulling at all in either mode. I tried locking the hubs just to see if that would help too, but made no difference. Only the rear wheels are working. There is no grinding noise or anything, just acts like a 2WD truck. I just started researching, but any suggestions? Are there electric or vacuum solenoids that might be bad, or is something completed shot?

 

When you have the cooling system set to the vents and shift to 4wd does it default to defrost? If you lock the auto hubs and then shift into 4wd with the dash **** does the 4wd system work?
Joe

 

I just checked both suggestions (Joe-M), and no the cooling system works normal, and no the 4wd does not engage with the auto hubs locked.

I also looked at the front drive shaft. I rotates freely in 2wd in D, but when I put it in 4wd, the driveshaft engages (either with the transfer case or front axle, but not both?).. How does this system operate?

 

Ok, it's a little interesting but I'll try and explain. When you put it in 4wd the switch actuates the transfer case with an electric solenoid. It also sends a signal to a vacuum solenoid telling it to engage the front hubs. If your vaccum solenoid is bad or you have a leak you can override this by turning the hubs to lock. If it still doesn't work I would say you either have a faulty hub or the transfer case isn't engaging but I would think that your t case switch is ok seeing as how your 4low gears engage. These trucks are known for leaks in the hub o rings, bad vacuum hoses, faulty vacuum solenoids and the occasional bad hub. Hope it helps.

 

hubs.

had the same problem myself, but i was in the dunes... not great without 4wd lol. stock hubs are junk, get some warns. you'll have to lock them manually, but you wont be fixing them again.

 

Sounds like your ESOF hubs are toast! However...before running out and buying new from the dealer (that is the only place that sells OEM)...take a look at this link.
http://guzzle.rbmicro.com/allube.html

Hope this helps...because the new OEM ESOF hubs are very $costly$.


biz

 

Thanks for the help guys! Guzzle's page is great reference too, thanks. The more I look at it, the more I think the hubs are f'd. Here are my ongoing observations, correct me at any point.. While both front wheels on the ground (in 2wd), Driver's side: In Auto-hub mode, cannot turn the knuckle/axle shaft. In Manual Lock-mode, cannot turn the knuckle/axle shaft. Does this indicate the hub is stuck locked? Passenger's side: In Auto-hub mode, can turn the knuckle/axle shaft, which turns the front drive shaft. In Manual Lock-mode, CAN turn the knuckle/axle shaft, which turns the front drive shaft. Does this indicate my hub is stuck unlocked or other problems? Or am I all screwed up?

 

your wheels need to rotate slightly for the hubs to engage.. trying moving a little and re-evaluate.

 

You have an open differential up front. One side should spin even though the other doesn't. Guzzle helped me through a similar situation about a month ago. The thread I started should be on here somewhere if you search on my name. It sounds like your hubs are engaing properly. Mine were not disengaging. There are two sysytems at work here to operate the 4wd, the vacume working your hubs and an electronic actuator runing your tranfer case.

On the hub side, start with the vacume switch located on the passenger side wheel well. Check with a vacume gage to see that you get a 16 inch mercury suction when turning on 4wd and a 6 in mercury suction when turning off 4wd. It was discribed to me as if clicking an ink pen. If you get similar numbers there, pull off the vacume lines from the hubs and check the vacume readings there as well (my lines had rust in them from the steel nipples in the hubs. cleaning the rust out fixed my problem).

On the transfer case side, i believe there is an electronic motor that selects the 4 wd and you should be able to see this working when the swtich is engaged. I didn't have to go that route, so I'm relaying what I've read from others.

In your original post you said 4wd wasn't working. As I mentioned above, you have an open diff up front and only one wheel will turn at a time (you probably know that, but want to be thorough).

See if any of this helps.

 

I think it is the electronic motor on the transfercase. With the switch in 4x4, you should not be able to turn the front driveshaft by hand.

 

In 4x4 the front driveshaft does not turn by hand. Check thread #3. I appreciate the help though. thanks.

 

My mistake. Hope you get it going.

 

In manual lock mode with both front wheels on the ground, you should not be able to rotate the axle shaft without the truck moving. Sounds like a bad passenger side hub. (Not locking in)

 

Thanks Yankeerider, those are my thoughts right now too. I'm going to double check once this damn rain stops. What happens in the hub to do this? Would there be a cam stuck/not locking in? Where are you in CT? I live just outside of Manchester.

 

The more I re read you post, the more it sounds like rust in the vacume lines. Pull those lines at the hubs first and make sure they're clean. Then try the system out. Both of my hubs were stuck in the locked position until I did this. It sounds like you have one stuckl locked and one stuck open. You're not getting enough vacume to overcome the rust blockage and trigger the hub to engage or disengage, if my theory is correct.