Several months ago I got my '53 3/4 ton fired up after a restoration. The first time I took it out, it was for a drive of just a couple of blocks. No vibration on that short trip. Several weeks later, I took it out for the second time. After a very short time (a block or two), I noticed a vibration at slow speed. Turned around and headed home. Vibration was worse by the time I got there. After advice from a previous post, I pulled the driveline today and checked for being in phase. It was out slightly, so I brought it into phase and took it out again. Still the same bad vibration at slow speed. The truck has all new tired and the wheels were balanced at the same time. I double-checked the motor mounts for tightness. I'm not seeing anything loose. It doesn't vibrate in neutral even revving. it is only under power. I have not tried increasing the speed to see if a faster speed ends the vibration because I'm afraid to do it. The vibration is significant at slow speed. It also has new u-joints and with it jacked up and in gear, I see no vibration in the driveline.
