So I got my '03 F250 in some soft mud the other day and threw it in 4 low but couldnt get out. I got out switched the hubs from auto to lock and pulled right out. I did engage the 4 low again later and it seemed to work on auto.

Why would it not engage for me on Auto? Why does it have the locking hubs?

 

ESOF equipped trucks use vacuum to lock/unlock the hubs.. The hub 'lock' position is a fail safe mode.. Could have just been a glitch since they worked later on when tested.. But there is an open TSB 04-18-5 for a non engaging/staying engaged/unlocking condition caused by axle nose to hub contact, anda service procedure.. You might try the 'auto lock' off and on a bit and see if they hang again..

 

What does TSB mean?

 

Technical Service Bulletin..