If I remember the vibes were worse with the new shafts, but that does not mean that they were installed correctly, with a dual cardin shaft you have to be within 2 to 3 deg of streight on the diff end so you have to cut and weld your perches front and rear, the rear will starve for oil if not a high pinion and your front will have steering problems unless you cut and roll the king pins for alingment and to clear your steering on the springs. I would lower your case first with just some solid spacers and see how you like it, I would Think that you would be just fine with that, the only thing I could see is shifter problems hitting the tunnel but a sawsall would fix that, the trail tough dual cardin they sell is 430.00 and has a 28 deg. angle to it and has only about 2.5 inches of travel on it. they use them on missing links. I'm going to be putting the t.t. missing links on my Black sammie and will prob be bolting them also, have the six pack yj's springs but will be pulling the small leafs off and putting the rear back to 11 deg. or so on the pinion, the guy I got it from got it from a kid in town and it has about a thirteen inch lift so thirty five mph is pushing it LOL I have stock shafts on it and have not had one fall out yet, the kid flopped it on each side on the con so it is way too high.