I can't seem to figure this one out and I need a second opinion before I start throwing parts into my truck. I have a humming noise coming from my truck whenever I am decelerating downhill or coasting. It tends to happen more when Im going over 45mph on the highway on an exit ramp. It sounds like its coming from the front end but I cannot tell. The noise gets louder as I brake.. If I hit patches in the road and the truck bounces up and down I can hear the noise go away and come back with the movement of the truck. I had the truck on a lift, couldn't find any play in the front wheel bearings or rear pinion bearing... Rear end play is normal. Im stumped.

Ill be looking at the truck again tomorrow at school.. any tips?

2000 Dodge Ram 1500 4x4 Sport 5.2L

Thanks