I listened carefully under the hood and couldn't figure out where the whining noise was coming from. I took the belt off and started the motor and there was no sound, so I knew it was a pulley. Since the idler and the tensioner pulleys are easy to access and cheap, I bought them at AutoZone, replaced, and the noise is gone. wow, the truck really sounds good without the whine. For $18 each, you really should change them anyway.

 

Might want to have done the tensioner arm at the same time too.....

 

I decided not to. Does the arm go through much range of motion at all, and thus wear out? what causes the arm to fail, in your experience?

 

The tensioner and idler are normal wear and tear components that SHOULD ALWAYS be changed when you change the serp belt. Although the tensioners only are recommended and published, you should catch the idler as well, since life expectancy is similar.

 

will do