Have an 07 2500 mega cab 5.9 4wd auto. Started noticing a slight vibration from a stop when towing or loaded. Was noticeably worse if you were turning while taking off. I'm not talking about punching it either, just gentle take offs. Vibration starred getting worse and would do it without a load. Checked end and it was a quart low. Added 75/90 oil. Still has the vibration. Checked ujoints and none had play but the rear one squeaked. Pulled driveline and couldn't move the rear most ujoint by hand at all. Replaced all 3 joints with new moog units. Drove truck about 11 miles home all was good. Drive to work the next morning and while making a u turn to park noticed a very pronounced shudder. Had a guy i work with drive it to verify. He pinned it down to being at 7mph and going away about 10mph. Thought maybe i didn't get the new ujoints centered. Put it on the lift and gave all the joints a good smack to help center the caps. No avail. Still shudders. Runs perfect as soon as you get below 7 or over 10. Front driveline is tight. Truck has 104k miles and the diff oils were changed by the dealer around 60k.