drive shaft angles

pitjeep

I put 1 3/4 lift shackles front &rear now has vibration at 40 mph I,ve got 304 with single exuast front d. shaft is almost hitting crossover pipe sitting still i think it is hitting on road and sterring feels alittle weird if i put shims in d.shaft will hit for sure i can probaly mod cross pipe how do i know what degree shims to get right now both pinons are pointing up alittle would i need to shim both f&r :razz:

jeepsr4ever

Whoa :!: thats alot of lift for a shackle. My rule of thumb is no more than 1" If your pinion is angled up too much you will have this problem but i doubt thats the case, you either have a worn ujoint or your exhaust is hitting-rubbing the driveshaft

Lifted79CJ7

I agree with MC, that is a loft of lift for a shackle. When you add that much lift on a shackle, you change the caster angle, which is what keeps your vehicle tracking in a straight line. The more you point you front pinion gear towards the sky, the worse the vehicle will handle. For the vibration, I would check your u joints as well. If they are well worn, they could start vibrating and eventually give out. I say check those and your bushings, also might as well go ahead and check your tie rods and ball joints while you're at it. These items all wear out and can cause a bunch of headaches when additional stres is added to the stock suspension. You mihgt want to put in a lower lift shackle - just a reccomendation. Let us know what happens! Jack

Mudrat

What other lift do you have in it? Concur with U-joints and suggest looking at dive shaft angles. If it's in 2WD your tranny output shaft and pumpkin need be aligned or the odd u-joint angles will cause that vibration too.
I was fine until I put a 4" lift in the YJ then vibrated like an eggbeater at 35-40 MPH. (I installed a SYE kit and Woods CV joint).

Check out the Tom Woods Page "Geometry 101" for some other clues.

Mudrat :mrgreen:

Lifted79CJ7

I agree with you Mudrat about the driveshaft angles (compared to pinion angle and output shaft angle on the transfer case). I just figured he already knew about that considering he was already talking about shims. I was just trying to think of other things. If a u joint is about to give, it can cause some vibrations, at least in my expierences(referring to really old u joints that have been on a stock vehicle for years). That would take some time to develope though, not just immediately after installing the shackles. Boy, I sometimes wonder about what I type when I'm tired! 111!!! Jack