Hello, I have had this problem for awhile, but I am trying to finally get it fixed. When slowing down or braking the truck will shake or vibrate from about 55 mph to about 40 mph and then becomes less. I have had the tires checked and now replaced, I have done the brakes and rotors, the u joints are good. The drive shaft is balanced. It feels like it is the rear of the truck. It shakes enough the change in the cup holder will make noise. What else should I start checking. Thanks for the help.