Drove the truck to work last week, noticed the truck vibrating at 60mph.  It went away when I sped up to get on the interstate.  When I left work I noticed it at 35mph and went away by 40.  It was off and on at 60 on the rest of the way home.  Under load or coasting didn’t seem to matter either. It doesn’t feel like it’s in the steering, just through the rest of the truck.   I did check the rear drive shaft and everything felt tight.  I had the front and rear shafts rebuilt and balanced when the trans was built about 50k miles ago.   The only thing I know is a little worn is my track bar,  was mentioned when I had the trans serviced last year.    The heat has kept me from doing any real investigating so thankfully it’s not a daily driver.   Just trying to think of something that makes sense as I really thought it would have been a drive shaft issue. 

Sounds like it maybe a tire balance problem.

That could make sense, I did have a new set of powder coated 3rd gen wheels installed not too long ago.  I’ll look and see if I notice any missing weights. 

I didn’t notice any missing weights, I jacked up all four corners and everything is tight.  I retorqued all the wheels to 120ft/lbs although they were all still tight.   I figure I can have the tires rebalanced just in case and get the truck on some jack stands and watch the drive shaft spin around to see if it’s out of focus. 

I got the truck on stands and ran it up to several speeds and drive shaft appears nice and smooth.  The tires looked odd though so next task will be getting them out on a balance machine. 

Had one rear tire out of whack.  Took it to schwabs and they did a road force balance on it, where they apply pressure to the tire while they balance it.   Never heard of that before but it did the trick.