I've been doing a lot of research on the forums to try to figure out the problem with my ESOF. Most of what I see is faulty hubs, and infrequent use. However ...I just had hubs replaced under warranty (originals seized) on my 03 F-350/7.3L/CC/DRW about 2-3 months ago, and have used it frequently without problems since. I have not yet trouble shot the vacume or electrical, but both seem to function fine.

Here's whats unique to my truck that I have not read on the hundreds of other posts on this topic: Unlike most cases ...If you switch the hubs from AUTO to MANUAL, I still get no front drive! Unique issue #2: If I put the truck in reverse ...I get fully funtional 4X4 in 4H and 4L, but as soon as I go to drive and move forward ...I loose the front drive?????????

The fact that I get locked hubs and 4X4 in reverse seems to indicate that all the vacume and electrical is working, and the hubs are new OEM.

The best indicator I have for a problem is that when I try to shift from 2wd to 4H "on the fly" ...I get something of a "grinding noise" coming from the transfere case (in forward only, works fine in reverse). It sounds like the servo is trying to engage the t-case, but just can't seem to go all the way. But why would it work in reverse, but not forward gears?? I'm not trying to shift at high speeds either ...just normal (below 15-20mph). In reverse I get an instant "clunk" and good 4X4.

Anyway ...it seems my truck is showing some "unique symptoms". Any help is appreciated.

-Sonic Blue

 

Just drive in reverse if you need 4x4 in bad weather Just kidding!! I'll give you a bump!! And welcome to FTE..

 

not an ESOF guy, so heres simply a bump

 

Yeah ...my first SuperDuty was a V10 with manual shift t-case. I won't do ESOF again.

Insult to injury ...I was going to just buy some aftermarket manual hubs and forget the ESOF, but discovered today that no one makes aftermarket hubs to fit a dually!

-Sonic Blue

 

I wish I knew more about the T case to help, it sounds like something is up there to me...Why only in reverse...that has me stumped...

 

I remember a while back a post where someone was having something similar and found his transfer case was loose. Loose as in the top bolts were backed out. Might want to check that as well as the shift motor. Vacuum lines could still be part of the problems, but can be determined by simply locking the hubs then doing the forward/reverse.
And I am almost 100% sure Warn makes a hub for your truck.

 

I've been having some ESOF issues myself but not quite like yours. From the sounds of it though, they are not engaging properly. If you are shifting on the fly and getting a grinding noise then the hubs are not engaging. Just like on older vehicles with manual hubs, the transfercase will not engage when moving unless the hubs are locked. Have you tried locking and unlocking them(with the transfercase in 2H) and trying to turn the axle joint by hand to see if they are engaging properly? They may just need greasing?