Track trouble

I have a hitachi 160 excavator. It has several hours and has had a hard life. The operator started digging today and said the left track would not pull its self. I assumed the track motor went out. Then he called back and said the left track is working but the other one will not pull its self. So I jumped in the truck and headed to the pit. When I got there the left track will not pull itself but you can hear a noise like it's spinning inside also it's like the tracks are in neutral....

Track trouble

Track trouble