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Vibrations - not so good ones http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=93&t=38089	Page 1 of 1

Author:	Glend [ Wed Dec 10, 2008 12:39 am ]
Post subject:	Vibrations - not so good ones
The Background: Since my lift the KJ has been 70mm (2.75 inches) higher than stock in the front, and 75mm (3 inches) higher than stock in the rear. There is no heavy front bar (just the Mopar Nudge Bar), and I now have the longer Polyairs in the rear (which I believe are responsible for the extra 5mm in height over the front). This is normally a lightly loaded vehicle on a daily basis and the carrying capacity of the Polyairs is really only used when towing the camper, the boat, or going on trips to the snow. The front end was aligned by Pedders (Grrr) after the lift and is set to KJ standards from the service manual. The problem: I now have a vibration that was not there before the lift, and that bothers me. It occurs under power at certain RPMs (most noticable above 2000rpm). I can sometimes feel it through my feet (thus the floor). Ocasionally it is like a beat frequency harmonic. It does not feel like anything is tearing itself apart but I am concerned about what this may mean over time. I would like some advice on this. Is it a common thing with a lift? Do I have to live with this? Do I need to shim the transfer case? Double Carden Joint? ???

Author:	cmohr [ Wed Dec 10, 2008 1:24 am ]
Post subject:
Could be toe-in/toe-out of the wheel alignment. Its hard to get a good alignment with bigger lifts, so the guys doing it must be good. I had quite a few issues getting a good alignment, that meant a shudder same as you are discribing, also bad tracking, and bad harmonic noise when driving in a straight line, Got a good alignment and all went away. Mind you I am running big lumpy tyres too, so that adds to the whole thing, but, even when I would change to my street tyres the noise and vibs were still there, until, I had it realigned.

Author:	smorison [ Wed Dec 10, 2008 8:15 pm ]
Post subject:
glen, i didn't have any issues once i had a good wheel alignment. take it to a 4wd aligner first if it persists then it may be something else.... worthwhile checking if it is speed specific or engine load specific (your 2k rpm mark, is that in any gear or after a certain speed). good luck cheers

Author:	Glend [ Sun Dec 14, 2008 2:40 am ]
Post subject:	Doh - Looks like some of it was my fault.
I forgot to tighten up the wheel nuts when I dropped it down off the jack stands (finger tight only). So Pedders aligned it with possibly loose front wheels. I found the loose nuts this weekend when I was going over it all once again. As soon as I found the first one I remembers that I did not torque them up properly. So now that they are tightened up properly things are better. I took it for a run on the freeway and the vibration is almost un-noticable. Now I am wondering if perhaps the alignment is crap due to the loose nuts. As suggested I'll take it to an 4WD alignment shop this week.

Author:	mikey [ Sun Dec 14, 2008 11:50 pm ]
Post subject:
Sounds like a good result, if not a little hairy!!! M.

Author:	smorison [ Mon Dec 15, 2008 1:16 am ]
Post subject:
Glen, you'll probably need another alignment as even 1mm out will cause vibrations... sucks mate but at least you found the issue! cheers from hot and wet singapore.

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