So I typically replace all the idler pulleys on my restoration trucks. The two stationary idlers are of course steel and I just replace the bearings in them because it is much cheaper than the whole pulley and I have access to a press. The factory tensioner pulley however is plastic with the bearings molded in to position. However the Gates pn 36102 is a steel pulley with a replaceable bearing, not than any of us will likely put enough miles on their truck to need another replacement.

Just thought I would share the info.

 

This explains a lot. I went to replace my tensioner pulley and found that the replacement I ordered was plastic, while the one in the engine was metal. Kind of a head scratcher since I figured that the original would have been metal like the idlers. Thanks!