I have a 03 Siverado ext. cab z71. I have a vibration at 45 and around 65-70. I have changed U-joint already and had tires balanced "fatory rims". Shocks?? I am not sure where to start on this one tires are not out of round and only have about 300 miles on them. I have shocks to put on it and also sway bar linkages. The truck only has 67k on it and my dad was the original owner.