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

[S.McArthur]

This is where I’m at, figured I needed to fix the leak and tore into the transfer case, found blue and red plastic shavings. Both from the speedo gears, I’m thinking the idiot that’s installed the SYE didn’t turn the gear to the proper tooth angle thing. A lot of crap inside the TC, going to clean it out really good and replace the speedo gears. Everything else looks just fine.

 

[AndyG]

Anybody that goes after it like you is going to solve problems.

The KO2 all terrain is what I run, it’s going to be a big step up in smoothness from what you have .

Stay on top of the drive shaft issue and make sure the u joint isn’t moving in the yoke .

You will have this behind you before long .

Then it will just be fine tuning.

I went through a lot of this same ordeal man ...one thing after another ...mine was a mess, could not be driven safely over 50 mph....now it’s 70 with one finger on beadlocks. Drove it from Huntsville to Gatlinburg Saturday afternoon before last , top down the entire trip.

Don’t let up yet. You will get it dialed in.

 

[S.McArthur]

Don’t let up yet. You will get it dialed in.

I think the hardest part is juggling the Jeep work and family time, lucky for me I guess, is that my son has been going to VBS in the evenings this week and wife finds activities to do while he's there. I guess it's just part of buying/owning a Jeep that had 6 previous owners and a lot of neglect, oh well, it's just money, I'll make more of it.

I'm jealous of the Gatlinburg picture, I love it out there. My dad came down a few years ago and we rode our Harley's to a cabin I rented out there. We made a 4 hour drive into an 8 hour excursion and had an absolute blast. The trip back was a little rougher, it decided to cool down (alot) and pour rain on us for about 1.5hrs, but, those are the memories you remember. We still have a good laugh about that one.

 

[AndyG]

I think the hardest part is juggling the Jeep work and family time, lucky for me I guess, is that my son has been going to VBS in the evenings this week and wife finds activities to do while he's there. I guess it's just part of buying/owning a Jeep that had 6 previous owners and a lot of neglect, oh well, it's just money, I'll make more of it.

I'm jealous of the Gatlinburg picture, I love it out there. My dad came down a few years ago and we rode our Harley's to a cabin I rented out there. We made a 4 hour drive into an 8 hour excursion and had an absolute blast. The trip back was a little rougher, it decided to cool down (alot) and pour rain on us for about 1.5hrs, but, those are the memories you remember. We still have a good laugh about that one.

Hang in there keep the family first and just don't give up on that jeep... It will smooth out and get down to worry about all you do is maintenance and enjoy it.

It's those adventures like that you never forget . Good stuff .

I came home from Gatlinburg with no windows in back that Sunday night .

I will carry windows in a fishing rod tube from now on ..noise about drove me nuts , and I could walk from where I am.

 

[S.McArthur]

New mount in after waiting forever for amazon to ship it, vibration gone even with front DS in. At 70 there is a slight vibe but I’m chalking that to the tires, you have to know to feel for it to find it.
Figured I was done, got the infamous P0303 check engine light, kind of knew something was coming, it had been running funny, figured it was the IAC but I suppose not.
Transfer case won’t shift in Neutral or 4lo, I think I bent something when I jacked the transmission/TC to fix all the nonsense. Savvy cable on the way to replace the OEM linkage.

Bonus: 2 nutserts or whatever they are for the trans/skid are stripped, I think I have some cancer. Whatever, I’ll get around to that.

 

[AndyG]

New mount in after waiting forever for amazon to ship it, vibration gone even with front DS in. At 70 there is a slight vibe but I’m chalking that to the tires, you have to know to feel for it to find it.
Figured I was done, got the infamous P0303 check engine light, kind of knew something was coming, it had been running funny, figured it was the IAC but I suppose not.
Transfer case won’t shift in Neutral or 4lo, I think I bent something when I jacked the transmission/TC to fix all the nonsense. Savvy cable on the way to replace the OEM linkage.

Bonus: 2 nutserts or whatever they are for the trans/skid are stripped, I think I have some cancer. Whatever, I’ll get around to that.

Keep after it ...the cable is killer.

 

[S.McArthur]

After a decent week or so of little to no vibration, it’s back. Someone pulled out in front of wife in here car so the Jeep is being daily driven while she drives my truck.
I’m not doing anything until I have her car back, so I’ll just live with it for now.
I’m going to have to get new tires just to rule those out, also going to get new control arms, I’m so sick of dealing with piss poor rough country garbage.
I have a list of crap to do, so I’ll update as soon as I get some time.

 

[AndyG]

After a decent week or so of little to no vibration, it’s back. Someone pulled out in front of wife in here car so the Jeep is being daily driven while she drives my truck.
I’m not doing anything until I have her car back, so I’ll just live with it for now.
I’m going to have to get new tires just to rule those out, also going to get new control arms, I’m so sick of dealing with piss poor rough country garbage.
I have a list of crap to do, so I’ll update as soon as I get some time.

Man it is so strange... I know rough country has the reputation as the entry level player.

I have a rough country long arm kit that uses a OEM 3/4 ton Dodge truck bushing... You would have to drive my TJ to believe it.

Of course it may be all over the road in a year....but right now I've had numerous people tell me it was the best lifted vehicle they had ever driven and these were pretty seasoned guys.

I'm not bragging on my vehicle by any means...it just makes me wonder why I'm having a good experience with something thats got such a terrible reputation.

 

[S.McArthur]

I'm not bragging on my vehicle by any means...it just makes me wonder why I'm having a good experience with something thats got such a terrible reputation.

My issue is that every thing that is adjustable/threaded is seized. It took 30+min to clean the threads on each control arm and track bar. Every zerk fitting have snapped out, not with a wrench, just fell out. On top of that, the bushings are slipping out, it’s just been replacing one thing from this kit after another. Other than the control arms and springs, I’ve removed all the RC stuff.
It was good in the beginning but things just started falling apart within 1/1.5yrs on installation. Just a pain to have to wonder if that is adding to my issues.

Rant over.

 

[AndyG]

My issue is that every thing that is adjustable/threaded is seized. It took 30+min to clean the threads on each control arm and track bar. Every zerk fitting have snapped out, not with a wrench, just fell out. On top of that, the bushings are slipping out, it’s just been replacing one thing from this kit after another. Other than the control arms and springs, I’ve removed all the RC stuff.
It was good in the beginning but things just started falling apart within 1/1.5yrs on installation. Just a pain to have to wonder if that is adding to my issues.

Rant over.

Amen... the bushings moving will kill the handling. Really will .

 

[Wtrask]

So I’ve owned my tj for 19 years bought it new in 2000. This is my first post and first post on a Jeep forum ever. I just wanted to add to the conversation on vibrations. I’ve dealt with them over the years and usually it’s a worn out part. I’ve had a bent mainshaft in my transfer case bad u joints bad axle yokes and bad drive shafts. The biggest issue I’ve had has been my front transfer case yoke nut loosening I’ve dealt with that a few times not sure why it does or how it does but it loosens up even with lock tite. Someone maybe covered this but this thread is long and I haven’t read it entirely. My 2000 tj also came with a harmonic dampener on the rear shaft. Thanks for all the info I have lurked off this thread to guys. It’s been very interesting to read thru.

 

[g.hayduke]

Here's a bit more anecdotal info for the vibration team to digest.

I have an '05 LJR with the 2.5" OME lift, DC rear DS, adjustable upper JKS CAs (rear) and Savvy upper CAs with Currie lower CAs (front), 1" MML and Savvy TT.

I had some minor vibrations that I almost eliminated completely when I installed the 4 front CAs and tweaked my pinion angle at the expense of caster. I could comfortably drive 70 - 75 (actual) with minimal vibes. This was with the stock front CA mounts on the front axle. Then things took a turn.

Wanting the full flex afforded by the Savvy upper front CAs, I had the Johnny joint kit installed. Well, now vibes are back. Anything near 70 or above produces the cyclic harmonic vibes I used to get only at 75 or above before adjusting the front pinion angle. So disappointing.

So what does this tell us? Not sure but here is my theory. First, the vibes are most likely originating primarily from the front axle and the imperfect pinion angle. I say this because the only change as far as I know was a change from clevite bushings to JJs on the upper front axle CA mounts. Second, the JJs on the front axle are better at transferring vibes to the frame than the old clevite bushings.

What am I going to do about it? Not sure yet. First, I'm going to check the front pinion angle and make sure the shop didn't mess that up. I'm also going to make sure the upper control arms are not fighting each other by disconnecting 1 side and making sure the bolt slips into the bushing without binding. Could be the arms are not at equivalent lengths and therefore compressing the bushings which would increase transfer of vibes through the bushings. Any other suggestions are welcome.

At 1 point, I was contemplating installing manual locking hubs but thought I had dodged that bullet when I got the vibes down to a minimal acceptable level. Now they are no longer acceptable and I have to do something to improve the situation. As my dear old dad used to say, "Dammit it all to hell!"

 

[g.hayduke]

UPDATE: Apparently, my theories were wrong. I got vibes tamed again to an acceptable level.

Pinion angle was almost 0 so that was OK. I got the vibes back under control by adjusting my front upper CAs. I loosened the jam nuts on both and found 1 had no tension/force on it at all while the other had a noticeable force on it felt by rotating the sleeve. I tweaked both to get the force as even as possible and get the pinion angle as perfect as possible. Re-tightened everything and test drove it. Vibes are back to where they were before. I can go 70+ with minimal vibes. Not perfect but I doubt I'll get to perfect without manual locking hubs.

 

[eastbloc]

Will add little bit more into the mix of theories.

After recent regear there was a grindy noise coming from rear every time i took a right turn or when driving on surface that was tilted to the left. Everything was fine at all speeds, other than that one thing.
Took it back to the shop, explained the situation and left it there.
Within 5 hours i get a call to come pick it up.

When i showed up, 1st question that was asked was if i took the carrier out and forgot some of the shims.
Me and mechanic both had a very puzzled looks on our faces, because i didn't understand where that question was coming from, and he didn't understand how could that have happened.
Turned out that carrier was lose inside of the dif, and considering the fact that it took them some time to hammer the carrier back in, mechanic didn't know what to say.
Either way, he added more shims, remeasured everything, and i was on my way.

Next day i get on the highway, and at 65mph i get the vibes. I slowed down and vibes were gone, then tried to reach 70, and as if someone flipped the switch at 65, again, i get the vibes. And they were bad vibrations, just as bad as they were before i fixed the pinion angle and did the SYE install. I was puzzled.

After taking the front drive shaft off, vibrations are still there, but are very minor in comparison and now appear between 68 and 75. They are constant and don't get any worse out to 80. I would say they are equivalent to the feel of poorly balanced tires.
Doubt its the tires though, before regearing i had this Jeep going 103 mph down the hill in Colorado, it was a "smooth" ride by Jeep standards.
I also had rear lifted and axle supported by jackstands while running it to 85mph, it felt okay, no shakes or vibes.


So that got me thinking, what if there is some imperfection in ring or/and pinion that is only noticeable under certain load at certain speed/rpm?
When my carrier was lose a little, there were no vibrations or shakes. I was driving 75 without suspecting and no reasons to suspect that there was something wrong in there.

 

[bobthetj03]

Will add little bit more into the mix of theories.

After recent regear there was a grindy noise coming from rear every time i took a right turn or when driving on surface that was tilted to the left. Everything was fine at all speeds, other than that one thing.
Took it back to the shop, explained the situation and left it there.
Within 5 hours i get a call to come pick it up.

When i showed up, 1st question that was asked was if i took the carrier out and forgot some of the shims.
Me and mechanic both had a very puzzled looks on our faces, because i didn't understand where that question was coming from, and he didn't understand how could that have happened.
Turned out that carrier was lose inside of the dif, and considering the fact that it took them some time to hammer the carrier back in, mechanic didn't know what to say.
Either way, he added more shims, remeasured everything, and i was on my way.

Next day i get on the highway, and at 65mph i get the vibes. I slowed down and vibes were gone, then tried to reach 70, and as if someone flipped the switch at 65, again, i get the vibes. And they were bad vibrations, just as bad as they were before i fixed the pinion angle and did the SYE install. I was puzzled.

After taking the front drive shaft off, vibrations are still there, but are very minor in comparison and now appear between 68 and 75. They are constant and don't get any worse out to 80. I would say they are equivalent to the feel of poorly balanced tires.
Doubt its the tires though, before regearing i had this Jeep going 103 mph down the hill in Colorado, it was a "smooth" ride by Jeep standards.
I also had rear lifted and axle supported by jackstands while running it to 85mph, it felt okay, no shakes or vibes.


So that got me thinking, what if there is some imperfection in ring or/and pinion that is only noticeable under certain load at certain speed?
When my carrier was lose a little, there were no vibrations or shakes. I was driving 75 without suspecting and no reasons to suspect that there was something wrong in there.

So, when you removed the front drive shaft and went for a drive the vibes were a lot less? Why do you think that is? Have you tried removing the rear DS and go for a drive in 4hi?

 

[eastbloc]

So, when you removed the front drive shaft and went for a drive the vibes were a lot less? Why do you think that is? Have you tried removing the rear DS and go for a drive in 4hi?

No, because my front DS and pinion angle have been neglected for some time. If driving just with front produce any vibrations, i will not be surprised.

Im fine with the way it is so far, i am a bit over geared for my tire size. Spinning 3000rpm at 70mph, that is 110mph equivalent on old 3.07 gears. Imo it shakes no worse than it was when i was rolling down the hill at 103mph.

Just here to share my experience, maybe it means something to someone.
When i go up in tire size, rpm will drop, if problem persist, i will start my own vibe chase.

 

[JDRAM11]

interesting , I will try that and just drive with the Front and see what i get

 

[Fouledplugs]

No, because my front DS and pinion angle have been neglected for some time. If driving just with front produce any vibrations, i will not be surprised.

Im fine with the way it is so far, i am a bit over geared for my tire size. Spinning 3000rpm at 70mph, that is 110mph equivalent on old 3.07 gears. Imo it shakes no worse than it was when i was rolling down the hill at 103mph.

Just here to share my experience, maybe it means something to someone.
When i go up in tire size, rpm will drop, if problem persist, i will start my own vibe chase.

I posted a theory earlier in this thread IIRC about genuine Dana gears and their quality vs aftermarket gears and their quality..Didnt get much off of that. However, I and a handful of other still agree that no one builds a better gear set for a Dana axle than Dana themselves. I think you might be on to something, but no one has ever documented a test like that. All that to say that I am doubtful it's the quality of the aftermarket gears, based on how many aftermarket gears swaps have gone without issue.

 

[joelachr]

Has anyone had these harmonic/cyclic vibrations on a stock Jeep? My 2003 Rubicon suspension is all stock as far as I can tell. I’ve had these vibrations since I bought it and originally chased wheel & tire balance to fix it. I threw new shocks and front hub bearings at it also in a fruitless attempt to cure it.

More recently, I’ve installed Centramatics and the vibe, while minor, is still discernible above about 65 mph. Both driveshafts are stock but have been rebuilt with new u-joints and balanced. Front axle u-joints were replaced. I clocked the front shaft at the axle and that helped some but didn’t eliminate the vibes.

Front track bar was replaced a couple years ago. I plan to replace the rear and all 8 control arms this year since I suspect they’re all factory original.

 

[Fouledplugs]

Has anyone had these harmonic/cyclic vibrations on a stock Jeep? My 2003 Rubicon suspension is all stock as far as I can tell. I’ve had these vibrations since I bought it and originally chased wheel & tire balance to fix it. I threw new shocks and front hub bearings at it also in a fruitless attempt to cure it.

More recently, I’ve installed Centramatics and the vibe, while minor, is still discernible above about 65 mph. Both driveshafts are stock but have been rebuilt with new u-joints and balanced. Front axle u-joints were replaced. I clocked the front shaft at the axle and that helped some but didn’t eliminate the vibes.

Front track bar was replaced a couple years ago. I plan to replace the rear and all 8 control arms this year since I suspect they’re all factory original.

What happens when you drive it without the front driveshaft?