Harmonic vibrations in Jeeps: A new theory (please read!)

freedom_in_4low said:

well that would have saved me about $250 on a new front driveshaft when mine ended up too long . How much runout did you measure?

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Enough to say "good thing i purchased this two yokes, few month ago, during my typical late night drunk Jeep shopping spree"

I have no tools to do such measurements.
What i did was lift front tires off the ground, disconnect rear DS, put it in 6th and let spin at idle speed. Then i put my hand on DS to get the feel for how even it spins.
After that, i used slow motion option of phone camera to capture DS spin at axle yoke, middle of DS and TC yoke. TC end had the most wobble

This is some really good info lads.

I re-geared my '97 2.5L/AX-5 with 2" lift on 33" tires from the stock 4.10 ratio to a Yukon 4.88 ratio. The work was done at a shop. After the re-gear i developed a noticeable harmonic sound that is most apparent at roughly 36mph (58km/h) at 1800rpm in 4th gear. Like most harmonics they have a certain frequency that seems louder than others, and the above mentioned speed causes it. At higher speeds the pitch of the harmonic sound increases and becomes less noticeable but the road/wind noise also increases so it's a bit hard to tell.

Anyway, just adding my two cents with regards to mystery harmonics and how they affect each jeep differently.