My dad's 08 Ranger threw itself into 4wd when I took off from a stop light. Switch is still 2wd. Any ideas on where to start?

 

2001 and up Rangers always have front wheels locked to axles

So you know its in 4WD because steering pulls you around a corner?

Just move selector to 4WD and then back to 2WD, if 4wd lights flash that means shift motor is not moving, if so then check fuse #27 in ENGINE fuse box, thats the power for the electric shift motor

Not sure this could even happen unless transfer case shift fork has failed

I have seen Rangers rolled and wrecked and they are still in 2WD, lol