vibrations--see if U can figure it out!! - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 11-04-1999, 07:32 PM
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vibrations--see if U can figure it out!!

I have an 89 wrangler, 3.5" lift, shackle reversal, sway bar disconnects, trac bar disconnect, 350 V8, turbo 350 tranny, 4.11 gears, dana 35 rear, slip yoke eliminator from currie, cv driveshaft from six states.

After installing the cv driveshaft and raising back up my t-case i had vibrations. So I found out I was suppose to have the pinion pointing at the t-case. So I did this and it was fine. then i broke a pin holding my springs to my axle pad. i lost the shim so I had to drive about 100 miles to get this fixed. The angle was now different on the u joints. i had the 4x4 shop install new axle pads welded at the correct angle so I would not have to use shims. When i drove home it was so smooth. but then it slowly started vibrating again usually about 55mph and faster. I do a lot of highway driving. So I looked at the angle and it looked like it was pointing up too far. it made sense--because it was really noticable when i gave it gas--the torque was causing the axle to move up and really getting the angle wrong on the pinion. so i put shims pointing the pinion just below straight toward the t-case. it was better but still vibrates. now it has gotten worse!! a lot worse!! and i've noticed when i let off the gas it stops vibrating. if i let off slow there is one spot on the throttle it really, really vibrates!! So what is the deal? Can you damage the u-joints running them at too many angles and this will cause vibrations!! It also feels like i have some slack in the line. when i let off it sorta makes a noise like the splines are loose?? Any help would be greatly appreciated! this is aggravating.
you can e-mail me at [email protected]

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post #2 of (permalink) Old 11-04-1999, 07:55 PM
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Re: vibrations--see if U can figure it out!!

The slack that you noticed is the big key. Were the u-joints new? I'm thinking they are since they most likely came with the cv drive shaft.....could they be damaged?....hard to should have gotten a lot of miles out of them....
Have someone rock the jeep back and forth in gear while you are under it....if you hold you hand on the drive shaft, you should be able to feel the slack...and maybe even see it. I'm also wondering why the vibration got worse with time. Did the springs settle? Once again, check the angle, if its right then it u-joints are suspect. Any chance your getting excessive spring wrap?...I wouldn't think so on a non SOA.

Lets us know what you luck.

John......southern CA
post #3 of (permalink) Old 11-05-1999, 12:29 AM
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Re: vibrations--see if U can figure it out!!

the centering ball may be damaged from running at an improper angle for an extended peroid of time. not uncommon with CVs. have your shaft checked out, because if the ball is bad and not replaced it will ruin the yokes. this gets costly. a good rule to set the pinion is tilt the pinion until its centerline matches the driveline centerline then tilt down 2 degrees. this will allow for pinion climb when you are on the throttle.

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post #4 of (permalink) Old 11-05-1999, 10:28 AM
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Re: vibrations--see if U can figure it out!!

This may be along shot, but my son's 74 Bronco was exhibiting the same kind of behavior. Drove us nuts, turns out the nut that
holds the yoke on the rear end was loose.

Brad (from the 4 Wheeling center of the universe, 4 corners USA)
post #5 of (permalink) Old 11-07-1999, 03:48 PM
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Re: vibrations--see if U can figure it out!!

Thanks for all the info!! I had a u-joint going out, replaced it and the trouble is gone. I guess when the pin broke from the leaf springs the side to side motion on the axle caused the u-joint to weaken and slowly get worse.

thanks again,

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