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Remus_Redbone 02-12-2012 10:10 AM

"Oscillation" at 55 mph and above
I've noticed a strange trait of my totally stock '02 TJ. It's a mild "oscillation" at highway speed. It's almost unnoticeable; the only way I detected it was while driving with electronic noise canceling earbuds to block out some of the soft top roar on a short road trip.

The occurrence is as follows; you can feel a very slight vibration that comes on slowly, reaches its peak, and subsides, all within 1 to 2 seconds. The "non-oscillating" time is also just a few seconds in duration, and then the oscillation comes back. The vibration is nothing like DW, and feels more like a very mild U-joint issue or maybe a slight out of balance tire, but the fact that it comes and goes in a very consistent interval tells me it's not u-joint or tire.

I just read a post about the harmonic balancer on the txfer case of '02 models and it got me thinking about this.

Anyone ever experience this issue? Is there any need for concern? Since I can't even detect it without the earbuds in, I'm not thinking it's too serious, but I've also been a believer that any vibration left unattended will get worse....:hide:

I-Want-A-Jeep 02-12-2012 10:12 AM

A tire balance/alignment issue can happen at only a certain speed consistantly..

ballistx 02-12-2012 10:25 AM

55 mph resonance
Tires have a natural harmonic at 55 mph. That is why most tire balance problems manifest themselves at 55 mph and above.

Anytime I get any vibration that shows up at 55mph, I immediately investigate something with the tires.

Remus_Redbone 02-12-2012 12:56 PM

"Oscillation" is at 55 mph AND ABOVE (any speed faster than 55 up to as fast as I've been, which is around 75). I haven't seen a tire balance issue that comes and goes at regular intervals while speed is constant.

Jerry Bransford 02-12-2012 01:02 PM

A rhythmic oscillation, especially if you can feel it coming up through the seat of your pants, is often caused by a bad u-joint on the rear driveshaft.

DaisyCutter 02-12-2012 02:01 PM

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I experienced this a couple decades ago, in a Z-car. I couldn't find the problem, it progressively got worse. I kept driving. Finally the u-joint partially separated and the driveshaft started rubbing the tunnel. Then I found the source easy.

I'd check the rear driveshaft.

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