Vibration 65-70 mph

Mine roars but it happens around 16-1700 rpm range no mater what gear I’m in. Very harsh vibration.

 

Did it change at all with the new steering tires put on? did you grab the rear drive shaft and ft. and try to shake it both ways or get a bar and see if you can see any back and forth play in them , does it have the U/joints that do not take grease or the ones you can put grease in ck them before you grease them if they are that type, run a string from trans. u/joint cap back to u/joint cap at rear end run a string down from center u/joint cap just to see if center u/joint is in line with both ends of string, ck to be sure all u/joint caps are in line and not off by any, drive shafts will vib. if all u/joint caps are not in line!

 

I’ve had one in the 1600-1700rpm at 45-50 mph for about 6 months now. Highway it cruises smooth.
On the carrier the bearing itself was ok but the rubber was shot and the output yoke nut on the 13 speed trans got loose and the seal started to leak because of it.
THERE WAS NO VIBE AT ALL before I replaced it and tightened the nut.

I’ve replaced all the joints with no change. I even reused two of the joints on another truck because they were still good. No issues there. They only had 33,000 on them. Played with angles by shimming the carrier. Rear diff angles and ride height are spec.

I believe after all the tests, checks, and things I’ve done that it is the trans. or the clutch. Something got worn when the rear bearing nut got loose. I don’t know how long it ran loose. If in 7 dir it is vibrating but when in 7 od at same speed it is noticeably harsher. The trans as far as I know has around 3 million on it. The clutch has around 670,000. They still function good and It’s drivable but annoying.

Weird thing I can’t explain is when the fuel tanks are full the vibe is lighter. When they get around 1/2 full the vibe is much heavier/harsher.

 

I’ve tested with or without trailer. No difference with this truck in that way.

 

The first thought was your steer tyres need a wheel balance yes something in there is out of sink that's for sure it should be smooth driving for you if everything was fine..

 

Does it happen both when you are pushing the gas pedal, vs when you let go of gas?

Does it happen in neutral vs in gear?

In my case the same exact symptom at 65 mph happened only when I apply the gas pedal , and it was a bad u-joint.