So just out of curiosity, has anyone had them look at the front drive shaft? For me, I feel the vibration at highway speeds just like everyone else seems to. However, if I drive in 4x4 Auto, the vibration is worse. Here is my thought. In 2wd, the clutch packs probably still allow spin in the front shaft, which causes the vibration. When shifting into Auto 4x4, the drive shaft is now under a torque load making it worse. In my truck, anyway, the vibration comes more from under the front floor boards than from the rear of the truck. Anyone have any insight/ thought?
I haven't looked yet, but if there is no slip yoke on the front shaft I may pull it out and drive it to see if the vibration subsides.