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

OP
psrivats

psrivats

TJ Addict
Supporting Member
Jun 4, 2018
1,553
OR, USA
Big update today.

My post re-gear vibrations are resolved. Yes! Finally!

Been working with a great local drivetrain specialty shop that's finally helped figure out the problem. There was no one root cause.

The on-vehicle balancing I posted a couple pages back helped. But not completely. The shop then replaced 2 items (front driver inner axle shaft and rear driveshaft yoke on the axle side), and adjusted pinion angles, followed by one more round of in-vehicle balancing. The vibes are completely gone as of this point.

I'm waiting for a detailed write-up from them and I'll post it here as soon as I get it.

Big thanks to everyone when has helped me and encouraged me and taught me. I owe you all a beer.

@JDRAM11 is going to try the same techniques at the same shop in a short while. We'll see if he has success as well.
 
Last edited:

Sudo

New Member
Feb 22, 2019
7
US
Yes, looking forward to the write-up.
Congrats on resolving the vibes. Sure hope more of us can benefit from the fix.
 

Chris

Administrator
Staff Member
Sep 28, 2015
38,127
Salem, Oregon
Believe me when I say that NO ONE here could have had the harmonic vibration as bad as @psrivats. I drove his after the gear install and it was nuts. At 40 mph that thing was vibrating like crazy.

IMHO after seeing and hearing what he has been through, the only place that can successfully fix this sort of vibration is a speciality drivetrain shop (like the place that fixed his) that treats the vehicle as a whole as oppose to just tearing it apart like Dave and Chris did at Jeep West, trying to replace every single thing and find the one thing that was bad.

It wasn't a case of one thing being bad, it was a case of a number of things needing replacing, and the vehicle needing to be balanced as a whole as oppose to just saying, "Well, let's try and balance the driveshaft and see if that does it.".

These guys clearly know their stuff, that's for sure. I look forward to your update as well @JDRAM11.

It seems like TJ owners may finally have a solution for an issue that has long plagued the TJ platform, with seemingly no solution (until now).
 
OP
psrivats

psrivats

TJ Addict
Supporting Member
Jun 4, 2018
1,553
OR, USA
Believe me when I say that NO ONE here could have had the harmonic vibration as bad as @psrivats. I drove his after the gear install and it was nuts. At 40 mph that thing was vibrating like crazy.

IMHO after seeing and hearing what he has been through, the only place that can successfully fix this sort of vibration is a speciality drivetrain shop (like the place that fixed his) that treats the vehicle as a whole as oppose to just tearing it apart like Dave and Chris did at Jeep West, trying to replace every single thing and find the one thing that was bad.

It wasn't a case of one thing being bad, it was a case of a number of things needing replacing, and the vehicle needing to be balanced as a whole as oppose to just saying, "Well, let's try and balance the driveshaft and see if that does it.".

These guys clearly know their stuff, that's for sure. I look forward to your update as well @JDRAM11.

It seems like TJ owners may finally have a solution for an issue that has long plagued the TJ platform, with seemingly no solution (until now).
I think you still need to check all the usual suspects.

I would strongly recommend anyone thinking of re-gearing to check everything very thoroughly BEFORE changing the gears. The gears themselves don't cause the issue (unless there is a setup problem), but the highly increased driveshaft speed will bring even small imbalances to the forefront. The vibration dampening methods (thicker skid, dynamat/noico) are need to address the resonance issues that arise on the side.
 
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mrblaine

TJ Expert
Supporting Member
Nov 20, 2015
5,339
Quail Valley, CA
I think you still need to check all the usual suspects.

I would strongly recommend anyone thinking of re-gearing to check everything very thoroughly BEFORE changing the gears. The gears themselves don't cause the issue (unless there is a setup problem), but the highly increased driveshaft speed will bring even small imbalances to the forefront. The vibration dampening methods (thicker skid, dynamat/noico) are need to address the resonance issues that arise on the side.
No different than any of our discussions. Each thing has to be checked and eliminated.
 

JDRAM11

New Member
Supporting Member
Aug 23, 2018
6
Hillsboro, OR
Mine is going under the knife to get some suspension work done, once it gets out, I Will take it to 6 states to get it evaluated as well. My vibrations lessened a lot, but I still have a very small one, will keep you guys posted.


Sent from my iPhone using Tapatalk
 
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pagrey

TJ Enthusiast
Apr 10, 2018
797
Los Angeles, CA, USA
It seems to point to bending ears when installing the u-joints on that inner shaft and rear pinion unless the factory tolerances are just not so good. Did the same shop/person do both of those? It is great that it's resolved.
 

tomtaylz

LJR Addict
Supporting Member
Ride of the Month Winner
Feb 18, 2018
1,974
San Francisco, CA, USA
Big update today.

My post re-gear vibrations are resolved. Yes! Finally!

Been working with a great local drivetrain specialty shop that's finally helped figure out the problem. There was no one root cause.

The on-vehicle balancing I posted a couple pages back helped. But not completely. The shop then replaced 2 items (front driver inner axle shaft and rear driveshaft yoke on the axle side), and adjusted pinion angles, followed by one more round of in-vehicle balancing. The vibes are completely gone as of this point.

I'm waiting for a detailed write-up from them and I'll post it here as soon as I get it.

Big thanks to everyone when has helped me and encouraged me and taught me. I owe you all a beer.

@JDRAM11 is going to try the same techniques at the same shop in a short while. We'll see if he has success as well.

Congrats! Now go enjoy that thing
 

ElectricWizard

Jeep Enthusiast
Supporting Member
Ride of the Month Winner
Sep 22, 2018
493
Portland, OR
Big update today.

My post re-gear vibrations are resolved. Yes! Finally!

Been working with a great local drivetrain specialty shop that's finally helped figure out the problem. There was no one root cause.

The on-vehicle balancing I posted a couple pages back helped. But not completely. The shop then replaced 2 items (front driver inner axle shaft and rear driveshaft yoke on the axle side), and adjusted pinion angles, followed by one more round of in-vehicle balancing. The vibes are completely gone as of this point.

I'm waiting for a detailed write-up from them and I'll post it here as soon as I get it.

Big thanks to everyone when has helped me and encouraged me and taught me. I owe you all a beer.

@JDRAM11 is going to try the same techniques at the same shop in a short while. We'll see if he has success as well.
Great to hear man! Patience has paid off in the end (y)
 
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Chris

Administrator
Staff Member
Sep 28, 2015
38,127
Salem, Oregon
Great to hear man! Patience has paid off in the end (y)
And he was soooooo close to selling it too. I remember getting many a text message from him saying he was done.

Looks like they solved it just in the knick of time!

In all honesty, I don't blame him either. That vibration was absolutely unlivable.
 
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ElectricWizard

Jeep Enthusiast
Supporting Member
Ride of the Month Winner
Sep 22, 2018
493
Portland, OR
And he was soooooo close to selling it too. I remember getting many a text message from him saying he was done.

Looks like they solved it just in the knick of time!

In all honesty, I don't blame him either. That vibration was absolutely unlivable.
That's honestly not surprising, most would've gotten rid of it a long time ago!
 
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AndyG

TJ Addict
Supporting Member
Jul 30, 2018
2,722
Alabama
Dude. Man I’m so glad for you , and hats off to the shop that solved it....vibes , squeaks and pops can be elusive Good on you for persistence. Almost all problems yield to persistence.

It’s summer . Smile , congratulate yourself , drop that top , drive and grin.

I agree something is to be said for all the brotherhood on here ...when a TJ doesn’t give you the love back, the forum can.

Really some cool, knowledgeable people on here, and that has value.