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

I changed mine . It didn't affect the vibe...but I think it's is a great idea to always watch those ... especially for handling issues .

I can see how they they could be in the mix in some cases. ..my gear shop agrees.
Which one did you change BJ, UB, or both?
 
And why would the harmonic change just by changing the tires?

Tells you how we perceive noise and vibration with our ears, eyes and body while driving the jeep. Your 50-60 vibe was a big puzzle for me and I'm very happy to hear it's now gone.

In your opinion, did the 50-60 vibe and the 65+ feel the same, or were there any differences at all?
 
Did yours change?

Yes, the 50-60 harmonic disappeared.

Tells you how we perceive noise and vibration with our ears, eyes and body while driving the jeep. Your 50-60 vibe was a big puzzle for me and I'm very happy to hear it's now gone.

In your opinion, did the 50-60 vibe and the 65+ feel the same, or were there any differences at all?

Totally different vibe. The 50-60 harmonic was a cyclic audible harmonic. Not felt so much, but more heard. The 65+ vibe is constant and felt in the seat, steering wheel, and floor board. Changing the tc skid to a thicker skid that raised the tc up 1" and sending the front ds to Tom Woods for a better balance have reduced the intensity of the 65+ vibes, but not cured it. Today I am replacing ball joints. I will inspect the unit bearings while I have things apart and report back.
 
Totally different vibe. The 50-60 harmonic was a cyclic audible harmonic. Not felt so much, but more heard. The 65+ vibe is constant and felt in the seat, steering wheel, and floor board. Changing the tc skid to a thicker skid that raised the tc up 1" and sending the front ds to Tom Woods for a better balance have reduced the intensity of the 65+ vibes, but not cured it. Today I am replacing ball joints. I will inspect the unit bearings while I have things apart and report back.

Totally get what you are saying. The 65+ is a resonance vibe and I have the same exact symptoms just amplified more. I requested Dave to check my unit bearings earlier in the week too! Let me know what you discover. Timken/Yukon replacements are not too badly priced.
 
blawll joibnts
Oh , shoot .I thought I was about to learn something amazing !

Here's my overall-

2003 Rubicon
31,000 miles
4" lift , 33" KO2 's at 26
4:56 Yukon gears
New unit bearings, knuckles , Spicer U-joints front to back , double cardan rebuild , Solid mechanically .

First regear -fail

Redid last month -win

I'm headed to Asheville N.C from Huntsville,Alabama in it now as I type (sons driving) , running 78 on the interstate .

Vibe almost fades past 70.

I'm rooting for you guys , but likely not going to chase mine .

It rarely sees over 65.

My sons a lead foot. He can also tear up an iron anvil with a rubber hammer. Good kid otherwise thankfully.

Reason for the low miles and new parts ...jeep was basically a wheeling toy before I got it ...basically needed trailered to trails the way it was set up . I wanted one more off /on road capable , so I began replacing everything that was neglected or had wear ..basically "city boy" types had it , didn't wrench on it I my opinion . That's a southern slant , and I'm not picking at anyone ...it's how you live ,not where , that matters.
 
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The only pain for me is I have to grind the unit beaing circumference down to fit the hat of my BBK rotors. Not terribly difficult, but a pain none the less. If the UB is bad, it is bad and needs replaced.
 
The only pain for me is I have to grind the unit beaing circumference down to fit the hat of my BBK rotors. Not terribly difficult, but a pain none the less. If the UB is bad, it is bad and needs replaced.
Hmm did you grind the current ones? Did you have vibe before and after or just after?
 
I put in new unit bearings .

What does bj mean ? Seriously
Totally get what you are saying. The 65+ is a resonance vibe and I have the same exact symptoms just amplified more. I requested Dave to check my unit bearings earlier in the week too! Let me know what you discover. Timken/Yukon replacements are not too badly priced.
check your axle u-joints while you’re apart too
 
check your axle u-joints while you’re apart too
Absolutely ..I did mine . My Jeep had sat ,and likely had seen some pressure washing ... Everything was stock and dry , as far as joints .

First time in my life buying low mileage kind of backfired , just goes to show ...it's maintenance and how/where the vehicle is driven and treated you need to consider ...as well as the lift components and bushings when you evaluate a purchase on a modified jeep.
 
Absolutely ..I did mine . My Jeep had sat ,and likely had seen some pressure washing ... Everything was stock and dry , as far as joints .

First time in my life buying low mileage kind of backfired , just goes to show ...it's maintenance and how/where the vehicle is driven and treated you need to consider ...as well as the lift components and bushings when you evaluate a purchase on a modified jeep.
Very true and one of the reasons I’m not a big fan of deep mud
 
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Very true and one of the reasons I’m not a big fan of deep mud
Going "mudding " is just mechanical suicide , and not only while you are in it , but it does damage weeks later as it works it's way into bushings , bearings , and Lord knows where .

Washing it helps ..but can also blast it in places .

It just destroys a vehicle ,etches paint , eats metal and plastic , and even causes gingivitis in most adults.
 
Going "mudding " is just mechanical suicide , and not only while you are in it , but it does damage weeks later as it works it's way into bushings , bearings , and Lord knows where .

Washing it helps ..but can also blast it in places .

It just destroys a vehicle ,etches paint , eats metal and plastic , and even causes gingivitis in most adults.
Don’t forget pinkeye

That is If by “mudding” you meant...
 
Finished up the ball joints. Everything looks solid. Unit bearings are tight and wisper quiet. Steering all looks tight. Brakes are in great shape. Sliders move freely, brake pads wearing evenly. No changes in vibes. The jeep is a joy to drive up to about 63mph now. Still need to figure out the pesky 65+ vibes.
 
Curious about whether anyone has compiled any data on this vibration issue that would help in trying to find a cause for why some vibe and some dont.

E.g. Is the cause related to faster rotating parts. Parts not "broken in together", and tolerances not stacking in a favorable direction.

Some have had luck reducing the amplitude by changing parts, how many have had success and what are those parts?

I find it interesting that some drive smooth with rear drive shaft out and others drive smooth with front driveshaft out.

Anyway, with data, it would help determine cause.

Would be interested if someone could setup a "survey" with specific questions and fixed selectable responses to help bucketize or narrow down possible causes.
 
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