Front End vibration 2001 2500diesel

[nick1]

Need help or an answer. have a vibration left front floor of vehicle At 30/40mph can notice. Have had tires changed,new shocks. front end checked,neg. Dealer checked front balls, and U-Joints. Everything O. K. Still can not find out what causes the vibration in front floorboard (Left)I only have 28,000 miles on truck 2001 Dodge 2500 Ex,Cab Lgbd. 4x4 diesel.