Why does my 4wd fuse keep blowing out when i change from 4hi to 2hi?

What is your question?

In 2wd the transmission sounds like something is spinning free so ive been driving around in 4hi but any time i change back and forth it blows the fuse every time. And when i put the transfer case into neutral it grinds when i take it out. Someone said it could be the 4wd position sensor what do you think?