ok, help me out if you can please. When driving the truck shifts great and rides great, until you get to between 45 and 55 mph. I can't tell if its a shutter shifting into overdrive, or maybe it needs plugs, or maybe something in the drive train. IT ONLY DOES IT WHEN BARELY ACCELERATING OR WHEN SPEED IS LEVELING OUT. if you drive quickly through 60 it has no issues. hopefully someone has had this happen before and fixed it. the only way i can describe the vibration is by saying it's almost like you're driving over road reflectors ....thanks