Problem with ESOF on 2K SuperDuty

Greetings - I have had trouble finding a forum whose members IQ is above room temperature. Hopefully this one is different!
Anyhow... for no apparent reason, my truck will not shift into 4WD when I twist the knob i.e. light does not appear (but does work!) and it does not shift the transfer case (hubs were locked manually). Auto hubs have not worked this winter either but manually were working fine ... worked yesterday on Berthod Pass but not today. I checked the obvious (damage, broken loose wires, fuses, relays etc) and found nothing blatantly wrong. Is this a common problem? I would investigate more but it is only 3° outside. Any quick and dirty suggestions? Local dealer has proven to be inept in the past so I think will take this one on myself.

This was a common problem we had on our race truck before I went to a manual shifting transfer case. It would hunt for 4wd. I would suspect that the cyliniod in the shifter is not ingaging in the cold weather. Does it seen to work good in the summer?

This was a common problem we had on our race truck before I went to a manual shifting transfer case. It would hunt for 4wd. I would suspect that the cyliniod in the shifter is not ingaging in the cold weather. Does it seen to work good in the summer?

Thanks for responding...
It has worked flawlessly (even the vacuum operated hubs!) until last month when the hubs began to exihibit a few problems (another story). Then it just refused to shift the other day. It has been cold (<32°F) for the last month. I am trying to trouble shoot with an Alldata reference guide but I don;t know where many of these components go or what they really look like. The truck has 135K miles and this is the first real issue so I can't whine too much... I was just hoping for a common problem/quick fix.

2/19/07
After diagnostics at a local shop, the GEM module failed (lost power windows, wipers, dome light...) $75, Replacement GEM module (@ Dealer) $350, Reprogram GEM (again @ Dealer) $200, do it all again (first GEM module faulty) $0, replace shift motor after ESOF STILL does not work $300.
4WD = not quite priceless, but very nice to have working again!
Next time manual case it is!