Ford shift on the fly - no 4HI

Like Grit mentioned above, it is possible for the transfer case to shift to 2 low, adding gear reduction, and the hubs still not locked, under the right circumstances. When shifting to 4 low, check for serious bind when turning, to be sure hubs are locking.

Jerry

Its easy to determine if it goes into 4 low. I put in N, flip to 4low, put in D and you can immediately tell because the engine revs up when giving some gas and I am going like 2 MPH.

I can tell its not going into 4Hi using the switch because I can flip the switch drive and turn the wheels and I get no binding at all.

If I manually lock the hubs drive and turn the wheel it will start to bind up so i know its in 4wd

austinjenna wrote:
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?

How are you determining 4 low is working but 4 high is not? I'm assuming that you are feeling it go into low range is why. You won't be able to tell if the transfer case is shifting into 4 high because the speed range don't change. The only other way to tell is look under the track to see if the front drive shaft is turning while the truck is moving. Do this with the hubs in the unlocked or auto position. Fords are bad about the vacuum hubs quitting. The transfer case will shift but the auto hubs won't engage. Have you shifted the hubs manually and then tried getting on a loose surface in 4 high and spinning your wheels?

Are you sure the transfer case is engaging the front driveshaft in any of those conditions?
With Fords, if you manually engage the hubs you get a slight bucking in the front end with slow turns even without putting power to the wheels and 4lo engaging may only be 2lo, unless you have traction tested to see if it's really engaged up front. (Note, the bucking on dry pavement while turning slow will be more pronounced if it's actually in 4wd)
Just something to check.
Can you hear the servo motor working to shift the transfer case?

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