ok im usualy in the first gen section butt my dads got an 04 3500 dually and it runs fine butt when he gets up past 65 it starts to shakes really bad butt when you get past about 73 it stops and drives fine if you could help i would appreciate it thanks

 

check the tires for a missing wheel weight and check the u-joints and carrier bearing on the rear drive shaft.

 

ok we replaced the u joints and that hadnt helped ill get the tirees balanced and let you know