Wife came in after driving the truck saying it sounded funny.....After investigating, I found that somehow the selector **** had been moved from 4x2 to 4x4L.....I know thats not good, considering the speeds around the DC beltway (75mph).

After searching online, the only thing I can find is that in doing that you may burn out the transfer case.....How do I determine what damage was done, if any? Or do I just need to take it to a mechanic and have it inspected?

 

There is a good possibility it never went into 4L. Otherwise, she never would have been able to do 55, let alone 75. At 55, the engine probably would have been around 6000 rpm. More likely it was in 4H and the main problem would have been that she was driving on dry roads while in 4x4. That could have caused driveline problems.