When driving my 2000 Silverado 2500 I get a vibration that only lasts a second between 60-65 mph. It happens only at acceleration and not on deceleration. I have tried to determine if the transmission is shifting when it is happening and it does not seem to be. It seems to shift at 55 mph on a normal acceleration and shortly after that I get a vibration, then it rides fine. It doesn't seem to be getting any worse, it just keeps doing it.
Any one else have this problem or know what the heck is wrong?