I swaped out my rear end for limited slip with 372 gears on my 67 4speed 400. now have a strong vibration at 55 and up. put in a new balanced drive shaft and taken it to a specialty shop on drive trains and pinon angle is fine and every thing looks fine.Vib was'nt there before the swap. If I raise the pinon angle 6 degrees up the vibration goes away about 95 percent but i'm told thats in the wrong direction and it will tear out my pinon gear. they think it might be in my transmison. anybody have any thoughts before I tear out my tranny or worse. Thanks Joe