2008 Chevy Avalanche Grinding noise when engine is cold

There is a grinding noise that comes from front passenger side of the engine bay when I start driving and the engine is cold. I only notice it when I stop at red lights and stop signs for a few minutes until the engine warms up. It does go on for a few minutes though. It's not a real harsh grinding, like the truck is shaking, but almost like the antilock brakes are purging or something - it's the length of time that it goes on that is troublesome. Thanks. And as far as donations go, we'll see from the response. Cheers.