Rear diff

At some point you pushed the locker button while driving around in 2HI, maybe trying to reach a fog light button. It won’t lock in 2HI.

You probably don’t go into 4LO often if ever. Your brother put it into 4LO to pull the stump, the button is still pushed in. The diff now locks because the computer will allow it.

After the stump was out, he left 4LO, without pushing the locker button to deselect it first. Now it won’t unlock because he’s not in 4LO.

Put the truck back in 4LO, make sure the locker button is deselected and drive it in a big slow circle until it clicks off.

 

Not being sarcastic at all, this is probably the best advice the OP has gotten in this thread.
That being said, I’m not totally sure cause this thread is a bit of a cluster but I think we’re past that and the truck is already at a mechanic and being messed with.

 

I certainly hope that "someone" is going to pay for screwing it up...

 

6 1/2 minutes of my life we’ll spent. I thoroughly enjoyed that. Thank you