Last year I put in a Grand National rear end , and a set of Lakewood lift bars, and had to have my drive shaft shortened, vibrated so mch that my drive shaft broke. Though it was just that drive shaft not being balanced, just bought a 3 " cromoly from Bear's Performance last week. Still has a slight vibration so can it be the lift bars? It called to set them at -6 preload so thats what i did, ANY HELP WOULB BE HELPFUL