2000 Dodge Durango

Some time ago while my wife was driving our durango it suddenly began making very loud grinding/clanking noise in what I assume to be the gear box. She pulled over and I went and got the car and drove it 4 miles home and it made the noise for me when I hit a bump and/or turned otherwise no noise. It sounded like the gears were clanking on the end of one another. A week later my son-in-law drove it and noticed the 4 wheel drive shifter handle was loose and it has made no noise since. It is full time 2 wheel drive like this and I need to get it fixed because in the winter around here we need it. Again shifter is loose. Could there be a simple answer to this, like pin fell out etc. And is the gear is easily accessible? I'm fairly handy with cars but need help with this before launching in.