power steering pump?

When i first crank my truck up in the morning it makes a humming sound that increases when i turn the wheel or accelerate. At first i thought loose belt but it's not a screeching high pitch sound (more of a hum) and it doesn't do it all the time. It stops after a couple of miles when the truck warms up. what do you guys think?

 

this must be a new record, 89 views with no replies!

 

Yep, most likely the pump. Mines been doing that for about 1 1/2 years. Getting worse recently though. If I turn fast like a quick U turn, it starts whinning for a few minutes until it calms down. Actually finally thinking about R & R.