My 2002 Dodge Ram 1500 with the 4.7 liter sounds like a bus when driving it.

My 2002 Dodge Ram 1500 with the 4.7 liter. At about 192,000 miles, I lost about 2 or 3 mpg, and it started to sound like a bus or a jet engine under the hood, and it seems to lose some power when it does this.  I changed the clutch fan (it was bad), and the truck was back to normal for about 6 months until it started again.  I have changed the clutch fan again, and now it does it almost all the time.  Before I changed the clutch fan this time, I would get going, and everything would get back to normal, and it didnt do it all the time, but since I changed the clutch fan this last time (4 days ago), it does it all the time, even at 70 mph!!  Please help me!!  
Also, this is not related to the above, but this last trip it developed a rather noticeable shake at about 55 mph, but it doesn't go away at higher speeds, just is not as bad.  I feel it in my seat, not the steering wheel.  Thanks