My truck started making a racket about 10 days ago and I knew my belt tensioner and one of my smooth idler pulleys needed replacement. Although I am not a "throw parts at it" kind of guy, I decided to replace all 3 idler pulleys, the belt tensioner and the belt considering that I was able to get them all for about $190. The other smooth idler pulley and the belt both could have waited, but I did them anyway. The grooved idler spun ok, but was noisy AF. The belt tensioner was obliterated and, apparently, had started to chew into my front cover. I caught it before it became catastrophic, but if I had kept driving for much longer the front cover would have been toast.
Here's the new one for easy comparison:
