I'm having an issue with my 4X4. I recently purchased a new to me 03 F250 6.0L. Went out today to test out the 4X4 in some sand, only to find out that for some reason, my front hubs don't seem to engage. I'm new to the auto/manual hub thing...traded my Tacoma for the F250. First I just switched the ESOF to 4HI...Nothing. Then got out and locked the hubs. This seemed to create the usual added workload for the truck in 4X4, but the front tires didn't move. I then switched to 4LOW. Same thing...Nothing. When switching from the dash ESOF, the lights lit up correctly and everything. Not sure what to look for here. Vaccum lines, electrical, worn hubs, transfer case? Don't know where to go from here, and am really bummed out because 4WD is everything to me. I like mud and mud likes me Thanks in advance for any help!

 

I'm new to my truck, but I've heard on older versions, when you locked the hubs, it was typically before you got stuck.. then the hubs would have to turn (drive a few feet) before they would actually lock in.

At this point, my spreading of old rumored info is "take it for what it's worth"... lol. Might be something to try though.

 

I had the same problem with my 05 F250. I worked on that thing for days tracing vacuum lines etc. Turned out to be a bad solenoid that engages the vacuum pump. I think it is a $60 part or so. I would try replacing that before you take it to a shop. The symptoms you described are the exact same I as was experiencing.

 

I hope I can get it fixed. That and also the popping/knocking whenever I turn the wheel...LOL. I'll check out the vacuum line and go from there. Don't want to spend $$$ when I don't have to. My hubs markings are worn down so much I can't read them. I don't know if I have manual or auto hubs. I assume auto. I have them turned clockwise right now for 2WD I believe.

 

Clockwise is lock. Counter clockwise is auto.

 

Also make sure you have it in Neutral for engaging 4wd low

 

The first thing is to figure out what is and isn't working. If the 4x4 and Low lights are coming on, it's very rare that the transfer case is not actually shifting into those gears. But it can happen. It's pretty common for the auto locking hubs to fail and need to be locked manually.

So... get the front wheels up off the ground with jack stands. Leave it in 2WD. Turn the hub lock back and forth three or four times, then put them in auto (counter clockwise). The front wheel and the front axle u-joint behind that wheel should turn independently of each other. This proves that your hubs are unlocked. Manually lock the hub (clockwise). Now the wheel and the corresponding u-joint should be locked together. The proves that your hub locks work and aren't broken. This would also be a good time to turn the front driveline. It should turn freely, proving that your transfer case is disengaged.

Now, with the engine running, turn the dash switch to 4WD. Check that the front drive line will not turn now. This proves that the transfer case has engaged. Check to see if the front hubs have automatically locked. Each wheel should be locked to the u-joint behind it.

When you've done these tests, let us know what didn't work right and we can help you fix it.

 

[quote=dchamberlain;10036713]The first thing is to figure out what is and isn't working. If the 4x4 and Low lights are coming on, it's very rare that the transfer case is not actually shifting into those gears. But it can happen. It's pretty common for the auto locking hubs to fail and need to be locked manually.

So... get the front wheels up off the ground with jack stands. Leave it in 2WD. Turn the hub lock back and forth three or four times, then put them in auto (counter clockwise). The front wheel and the front axle u-joint behind that wheel should turn independently of each other. This proves that your hubs are unlocked. Manually lock the hub (clockwise). Now the wheel and the corresponding u-joint should be locked together. The proves that your hub locks work and aren't broken. This would also be a good time to turn the front driveline. It should turn freely, proving that your transfer case is disengaged.

Now, with the engine running, turn the dash switch to 4WD. Check that the front drive line will not turn now. This proves that the transfer case has engaged. Check to see if the front hubs have automatically locked. Each wheel should be locked to the u-joint behind it.

When you've done these tests, let us know what didn't work right and we can help you fix it.


I will definitely try this!

 

Subscribing, what became of your investigation, sounds just like what happened to us today.

 

I'm sorry to bring this thread back...
Ive been reading and reading and learning some tests Im gonna have to perform...
First off...my 4wd was intermittent at Mammoth last year...then nada...First ever problem with it.
No 4wd light on dash via switch..

So I just performed my first test.... Turned on key switch...waited for buzzer to go off...toggled 4wd switch to 4hi.....and I can hear the relay under the hood make n break 5 times...
Any ideas folks ?

Thanks in advance !!!!

Ooops....03 f350 7.3 cc lb srw

 

Wait, wait, wait. There's no need to endanger yourself or others by jacking anything and locking things while in gear and all that.

1. The system is operated with vacuum. First thing, verify that you have vacuum. Can you switch HVAC from defrost to the floor ducts? If not, check the plug connecting three vacuum lines to the HVAC unit behind the glove box. If you remove the glove box, it will be to the upper LH corner of the glove box "hole".

1a. If this is disconnected (it happens with people's feet hitting it), reconnect and test again.

1b. If you still have no vacuum after verifying the plug is connected, go under the hood on the passenger side fender well, just aft of the battery and forward of the HVAC unit is a vacuum pump. With the key on and engine running, unplug and plug back in the vacuum pump connector. Does the pump run? If not, you have a bad pump. But wait, there's more. If it does run, go see if you can switch from defrost to floor. If you can, shut off the truck, disconnect the two tubes connecting the vacuum pump to the vacuum accumulator can to relieve vacuum. Turn the key to "on" but don't start the engine. Does the pump run? If not, the pump is bad, but again, wait. there's more. If it does run, you have a vacuum leak between the ESOF solenoid and the hubs.

2. Now, I know what your're thinking. Why is he saying "wait"??? Because if you have a bad pump, you HAVE a vacuum leak. The only ways that the pump fails is due to overheating from running constantly, or a bad segment in the armature of the electric motor, also due to heat. So, if your's is bad and will not operate, get yourself a vacuum tester from harbor freight and start pulling vacuum on everything. The accumulator, the hubs and the lines. Start at the line connecting the accumulator to the hub solenoid, if it leaks, pull the line off the solenoid and test the lines going down to the hubs and so on and so forth. I've owned several Super Duties since 1999 and nearly every time I had an ESOF problem it was always due to a leak in the tubing near the knuckles. I just replace all of it when I find a tubing leak.

The Dorman brand vacuum pump that is $50 on rock auto works great. I've had one now for three years in one truck.

 

[QUOTE=Thor'sHammer;16295951]Wait, wait, wait. There's no need to endanger yourself or others by jacking anything and locking things while in gear and all that.

1. The system is operated with vacuum. First thing, verify that you have vacuum. Can you switch HVAC from defrost to the floor ducts? Thanks for the reply Thor !!! Yes... my vacuum pump works fine.... I can switch between floor... dash and defrost vents well...no problem there yet... The 4wd Hi relay closes/opens 5 times in succession after switch selecting 4wd Hi....and then nada...no dash 4wd light....no shifting at the transfer case selector unit...nothin. Have you any ideas Sir ? Thanks :-)