I finally found the vibration that has been eluding me in the truck for the last 10 months.  I went through all possible things to check and found that it was a bad brake drum.  I think that it was a deformed casting from it's conception.  I had to go through 3 new brake drums to finally find a good one but now the truck rides on the interstate as good as my wife's Town and Country.  

 

I am doing my happy dance and now it is time for a cold one.

 

Thanks to all who offered suggestions along the way.  Many times you never hear what the cure was when someone has a problem so the reason for this message will help others who may be trying to find the vibrations problems in their trucks.

 

 

   

Edited March 22, 201510 yr by lcattin

Oops.  This was supposed to be in the 24 valve forum if someone would like to move it.  Sorry.

Oops.  This was supposed to be in the 24 valve forum if someone would like to move it.  Sorry.

 

Fixed for you...

I had a warped Rear disc (with drum parking brake of course).  Chased it for over a year.  Dealer couldn't find it.  My regular shop couldn't find it & I stopped going there.  Took it somewhere else, explained the situation, found it first try.   It wasn't always like that. 
 

It was intermittant because I don't like to use the brakes hard...  If I plan my maneuvers right, I barely need brakes...  so the rears weren't taking up most of the time. But when they did, it chattered.   

This drum was so distorted on the outside of the casting that at 68 to 70 the whole truck would just shake and the door panels would rattle.  So Glad to have it fixed.