2004 Ram 2500 has vibration felt in steering wheel starting around 50 mph subsides around 63mph and returns again at 74 mph. Vibration is light (feels like holding a back massager). But can be heard at higher speeds. Front u joints are new and front drive shaft is new (old was broke at the double knuckle) when purchased. So not sure how long it was driven like that. However vibration subsides if place in 4 wheel drive? Any suggestions are appreciated