Ford shift on the fly - no 4HI

[austinjenna]

2010 F-360 6,4L
My electronic shift on the fly will not engage in 4 HI. It will go into 4 low, comes back out into 2HI just fine, just no 4HI. I can manually lock the hubs and it will work, just not from the dash switch. The light on the dash does come on as well if I use the shift on the fly.

Since I can manually lock in the hubs and it works I have eliminated the hubs. I tried the defrost/vent trick and it works as it should. I know these things work on vacuum and since its going into 4low I can eliminate a vacuum leak. Im just trying to debug it before going to the dealer.

Any ideas on where to look?

[MFL]

What you describe, makes it seem as though the dash switch may be faulty, if vacuum lines are functional. Have you tried going into 4H, like shifting to 4L, by stopping, putting into neutral, then shifting to 4H? Has there been any previous issue, or just all of a sudden not working? More info could be helpful, for armchair diagnosis.

Jerry