Good afternoon. I have a 2002 F250 6.8 V10 4x4. (Manual WARN Hubs) I was recently towing my boat on the interstate doing around 70 mph when I heard a terrible grinding noise and noticed that my 4x4HI indicator light came on. I realized that the truck had shifted itself into 4H without me ever touching the switch.

It was in the middle of the night so I slowed down to a crawl, pulled off at the next exit and using the electronic dash switch attempted to get it back into 2H. No luck, it wouldn't come out of 4H. I got under the truck and disconnected the harness on the transfer case and attempted with the switch again. Still won't come out of 4H.

With the transfer case disconnected and the selector switch in the 2H position, I disconnected the battery and let it sit for a few minutes. Once re-connecting the battery and starting the truck it finally went back into 2H.

I left the transfer case disconnected and continued on to my destination. After our vacation and the 500 mile journey home, I reconnected the transfer case and tested all modes of 4x4 with no problems. I have not driven the truck much as it is strictly a tow vehicle (maybe 50 miles) with no issues.

Other than completely scaring the crap out of me, I was very concerned that something had torn up but everything appears to work as normal. None the less, I'm about to embark on another long journey with boat in tow and DO NOT want this to happen again. Has any one else encountered this issue and if so what was the culprit?

I have read through another post on the forum about a similar issue regarding an F150. This gentleman and some forum experts could not nail it down and the truck ultimately ended up in the hands of a Ford tech. Also, his problem was in his GEM module and if I'm not mistaken my truck does not have one of these. I believe the responsibilities of the GEM was replaced by multiple modules in this truck.

Any help would be greatly appreciated. Thanks.

 

You may want to post this in the super duty forum since it is not engine specific. A lot more eyes on that forum.

 

Never mind. I see you already have it there.

 

GEM get wet? Or did the GEM go away in 2002?

 

I had a very similar experience with my 2000 GMC sonoma highrider- almost to a T. Just like you I'd be traveling around 70 mph and start to hear a grinding whine. I would slow down and sometimes it would kick back to 2wd but most time it wouldn't. The only fix would be to disconnect the battery and let it reset. For a while I even kept a 5/16" wrench on my key chain.
It turned out to be a rusted actuator. For some reason there was a tiny amount of water inside the system. It would still pull a vacuum (don't ask me how) even though there was water in it. Once we figured it out it was a quick swap but it was too late- the differential was ground down. I ended up trading it in for my first Ford. Hope this helps.