Hey guys, I'm having an issue with my front hubs in my 2008 F350 6.4 Diesel Harley... To engage 4x4 inside, it's just the **** that i turn, not a floor shifter.

The transfer case engages, but the hubs won't lock. I have to get out of the truck, take off the wheel caps and manually turn the hubs to "Lock", if I keep them on "Auto" nothing happens, only RWD works...

I think I read somewhere that these "Auto" hubs are vacuum actuated. Could the hubs be the issue and not holding vacuum? Or is there some vacuum pump that could be broken? The truck has 70k miles on it, so it's out of the powertrain warranty where would I start diagnosing this problem?

 

Also, do you have to be rolling to engage 4x4? I only tried engaging it when I was already stuck in the sand. I read in one of the threads that the hubs will only lock while rolling?

 

No, you do not have to be rolling to engage 4H.

Until you can fix them, just lock your hubs manually when you need 4x4.

The hubs do not "hold" a vacuum, it is more like a vacuum pulse engages them.

Do a forum search on ESOF, you will find a ton of information on what to check and fix.

 

from what I was told there is a seal in each hub that will need replaced to fix the switch activating 4x4, a wide rubber seal in the hub, $45 part, I have the same prob. I asked in thread of the time and dificulty in repairing this, but you are on the right track.

 

That may or may not be true. The issue could also be a torn or unplugged vacuum line, a vacuum leak, a weak vacuum pump, a bad vacuum solenoid or a bad (slagged) hub. Each will require being looked at to determine the point of failure.

Blindly telling someone it is a "seal in the hub" isn't helping and may be hurting the issue.

As I stated earlier, do a forum search on the term "ESOF" and start studying.

 

sorry, just what mechanics told me about this, they say the seals are usually shot after 100k miles...most common, and a possibility, should have said that. do let us know th outcome...

 

I always heard the wheel needed to rotate just slightly, like 1/2 turn to fully engage, that if you were already stuck it was too late (to auto lock). To the OP, have you tried the ESOF since you got out?

If it still doesn't work, you likely have a vacuum leak, you'll just have to start tracing lines. A vacuum gauge would be a big help as well.

Could also be the o-ring on the hub, and that's probably a $4-5 part. If just throwing money at it, I'd check that first. I'm no expert on ESOF but not even sure what seal that would be.

 

truck does not need to move to engage the front on the later models.

If you hvac defaults to defrost then it is a sure sign of a vacumn leak.

 

i just got the truck back from the dealership after some maintenance work. tried the 4x4 while driving. i felt it engage. The steering wheel got tighter and felt like the wheels were binding when turning so I think the hubs may have locked. not sure though. I did head the vacuum pump turn on when I engaged 4x4, then i heard it again after I disengaged it. does that sound right?

 

yes...just verify if the hubs are in auto or locked as well.

Also it is a good idea about once a month the manually lock the hubs and drive a little.

Keeps it all working right.

 

they are in auto... the dealer did replace some vacuum lines in the engine bay they said. so that may have fixed my issue

 

If in "auto" tires need to be slightly moving but not spinning out, to engage. if done manually you can be sitting still. Thats what my owners manuall says. I even verified it in the snow. some times it even takes 10-15 ft to engage in the snow when hubs are in auto.

 

Keep a eye open for the vacuum hose on each side. They generally start to dry rot after a couple of years. I change mine out every 3 years. Cost maybe $3 for hose. I haven't had your problem reoccur again. Also, watch for any diesel leaks. Diesel will flare these hoses up.