lets start out as i have 2006 Dodge Ram 1500 4x5 with 5.7 Hemi . I just bout the truck two Months ago and knowing the we’re a few small issues when I bought it. Normal wear and tear. What I’m having problems trying to track down is a slight vibration that only happens 60mph and above and continues past 80. This vibration is felt through the seat and floor board. Also only happens when I’m on the throttle holding 60mph or above and the vibration goes away after I release the gas petal. This is what I have done
new drivers side CV and shaft that goes into diff. Due to too much play witch wore out the differential shaft
replaced all the tires and have had them rebalanced twice
new front struts
replaced the driver side motor mount bushing as that was split and the passenger will be tomorrow
then drive line was completely rebuilt, everything new except tranny yoke. Work done by drivlines nw
front and rear differential oil services
before all this work the vibration was way worse.

Next on my list is
alignment as that’s off
front seat bar bushings are cracked and bad
rear shocks I’m replacing they seem wore out
bushing on passenger side leaf spring the front one not the shackle ones are torn and a can see leaf spring to frame rub. Replacing all those with good Polyurethane bushings last I noticed when installing new drive line the pinion flange on rear differential I was able to 1/4 turn or so and It would slightly move in and out of the differential. I don’t know what I’m going to do there. Any other ideas would be helpful. Thanks