1993 Ford Truck Ranger 4WD 3.0L MFI Making Noise
 

I have a 1993 Ford Truck Ranger 4WD 3.0L MFI that is making noise when I get up to the speed of 60 MPH. It sounds like a Hum/Whine sound coming from the truck. I just replace the U joints that bolt to the transmission. What can be wrong going wrong? I drive 600 miles twice a week, need to find out what is wrong with it so I not setting on the side of the road. Thanks for your help.