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Vibration!!!HELP!!!!!

KTMarquardt

NAXJA Forum User
Location
Wisconsin
alright so i have a 97 XJ that i purchased for $500, had some dinky lil 235/75s on it with a 3in lift so i immediatly upgraded to 31s. after that i began to get a very bad vibration under load and also at speeds above 30mph. i shimmed the rearend to raise my pinion angle, had the front and rear drive shafts balanced, and also installed drop blocks for the transmission crossmember. It took care of most of my problems except i still have a vibration at around 50+. i was wondering if anyone else has ran into this issue or have words of wisdom. ive already checked my front end parts and aligned the front end and also aligned my track for the rear axle....Thanks
 
Just a question. Did you loosen your motor mounts before dropping down your crossmember, and then re-tighten them back up to spec?
 
castor and toe numbers?

tires in good shape and balanced? tried rotating them?

did you do the 6/12 and 3/9 check for BJs and unit bearings?

if you dont have a SYE, i think your supposed to leave your T case output and pinion on the same plane. not shimmed like a SYE.

do you feel the vibes are coming from the front or the back?


please explain what "aligned my track for the rear axle" means. ive heard of thrust angle... if this is the same thing. but without some fabbing, you really shouldnt be able to adjust it. and having it a bit off wont cause wear, so why change it?
 
I work at an alignment shop and by track I do mean thrust angle. The Jeep dog tracked down the road terribly after the rear shims. Caster, camber and toe are all aligned, vibration seems to be coming from the right front. I took a thermometer to the front end and compared the wheel bearings and axle joints and everything was even nothing majorly hot. I was wondering what kind of mods your supposed to do to the front track bar with a lift. Mine looks like its mounted in the stock position
 
I just got through fixing a wierd vibe in my Exploder thanks to Jon Jacobs and a lift at the Ford Dealership. While it looked fine and seemed fine on the car, I had a bad ujoint on the rear drive shaft. I would have sworn that the vibe was comming from the front.
 
alright so i have a 97 XJ that i purchased for $500, had some dinky lil 235/75s on it with a 3in lift so i immediatly upgraded to 31s. after that i began to get a very bad vibration under load and also at speeds above 30mph.

I would have stopped right there and asked myself; "Self, what did I change to get vibrations?". Tire balance can cause all sorts of issues from "The shakes", to "Vibrations" to "Death Wobble".

i shimmed the rearend to raise my pinion angle, had the front and rear drive shafts balanced, and also installed drop blocks for the transmission crossmember. It took care of most of my problems except i still have a vibration at around 50+. i was wondering if anyone else has ran into this issue or have words of wisdom. ive already checked my front end parts and aligned the front end and also aligned my track for the rear axle....Thanks

From what you wrote, it appears you have changed the driveshaft angles without first finding out if they were even in the ballpark.

Remove the rear shaft and make sure the u-joints are OK. They should orbit smoothly. Anything less, and change them. Next, measure the driveshaft angles. That is the angle between each Yoke and the Driveshaft.
They should be equal and opposite within a degree or so to cancel out.

Don't forget the front shaft U-Joints. If they are bad, you can end up with a vibration also. The front Pinion should be in-line with the drive shaft. A degree or two low is acceptable. Never pinion UP.
 
I replaced all joints in the driveshafts replaced when they were balanced, the rear driveshaft angles are equal. What am I supposed to use to shim the front end? Shorten the bottom arms?
 
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