I have a 2000 F350 dually V10 super duty crew cab.
I went off road and switched it into 4WD with the switch on the dash.
Bottom line is it isn't going into 4WD. Have never had any trouble with it before.
Later in my yard when I switched to 4Wd HI ,while moving, I could feel something like going into gear but it still dosnt work for 4WD.
Going to neutral and selecting 4WD LO I hear a distinct clunk and the truck starts forward with parking brakes on.
4WD lo seems to work but not 4WD hi
The owners guide says relays 40&41 are the shift on the fly relays. but the diagram in the book only shows up to #37
Where are 38 thru 41?? (I did find 2 relays I believe to be the right ones and they test good)
Any idea what's going on here?
thanks as always!
Tk

 

If you have the ESOF,then you probably have auto lock hubs[vacuum operated hubs] loss of vacuum might be your problem,follow & check vacuum hoses for leaks,or manually lock the hubs to bypass the need for vacuum signal to trouble shoot.

 

I had to replace the vacuum hoses under the front fenders, behind the wheels. They were rotted. I have 4WD now and it shifts 'on the fly' But it wont come out of 4WD (even tho the light is off) unless I stop and go in reverse then it does.
Even that didn't work to bring it out of 4WD after a few times. Then it did. But now I have a distinct klunk klunk in a tight left turn.....but not in a rt turn.
Now what?
thanks as always
Tk

 

backing up to get out of 4 wheel is what you have to do to unlock the auto hubs.
the clunking could be a bad front axle universal joint