Ok. Got a 97 F 250 with a 5 speed, 4:10's, and the TTB front axle. Truck runs great and smooth till I hit 60 mph. Then all of a sudden it gets rough and real noisy. Then at 70 mph it flattens out and gets nice and smooth again. Really wierd. Although at 70+ mph she's screamin but I've takin it outa gear at 65 mph and the roughness persists. So it isn't the tranny. And I can definately feel it in the front end over the rear. Truck has 144k and the ball joints and u-joints were new at 135k. And Thier still fine. What do ya guys think? Thanks.