My wifes 07 Expy developed a whinning noise from the engine 2 days ago. The tone changes with engine RPMs. The truck has 176,000 with the original idler wheel so that is my first suspect. Anybody else have any other ideas?
Thanks

 

Well I pulled the belt off and all the idler wheels spun freely and had no play in them, DAMN! I was kind of hoping the solution was that simple. Im trying to think of what else could cause a whinning sound. Power steering pump? AC compressor?

 

Start it up with the belt off and see if it is now quite.

 

Check power steering fluid...

 

Did you check the tensioner? I had a bit of a chirp that changed in tone with RPM changes and that was the culprit. Water pump bearings will squeal when they go bad as well.