vibration around 40MPH (3rd to 4th gear)
Recently, and after I've replaced my upper and lower ball joints (couldn't be related), I'm now experiencing a vibration when the truck is mostly shifting from 3rd into 4th gear. This also happens often when I'm gunning the engine up a hill. It feels like I'm driving over a consistent strip of a rumble strip. As a matter of fact, when this first started to occur, I tought I was going off of the road!
Other than this problem, my truck runs great. If anyone has experienced and solved this problem, and would like to help me out, this would be greatly appreciated.