How do you know when it's time to change timing chain?

Car just started sounding a lil different. Like a lil samford and son truck sound I flushed engine after car been sitting for 2 week. It still rides good but I can't put my finger on it.i recently dropped tank too so I'm not sure if the exhaust wiggled so.e because I was smacking it on there upon removal. Would a quick video help??