That could be one of them, the stock drive shaft likes to have both flanges parallel(sp) the toyota drive line would be good but there are two diffrent ones that I know of, one is no better than the stock sammie one that you have now, hardly any flex to it at all, I think the one you want is the earlyer one,I would still get rid of the shackles to get it closer to 6.5 inches of lift and get rid of the drive line spacers and go with an extended yoke and grind the ends of the drive shafts a little the part that holds the u-joints in that would hit each other while flexed all the way, have fun.