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

[bobthetj03]

I hope you guys can figure it out. I'm 2 years and counting and nowhere closer to solving it. I'm not giving up though. I have a trickle of hope that Tom Woods may find something with my front DS, and now that I'm driving without it, I will play with rear pinion angles some more to try and remedy the harmonic.

 

[psrivats]

Part of me is tempted to tell you to just put the 4.10 gears back in, but I really don't want you to do that, as a problem like this will drive me nuts (even though it's your problem) until there's a resolution. I'm not the type that likes walking away from problems and accepting defeat.

I'd be OK doing that if Dave tried everything and told me he can't fix it. But without trying, it's a hard thing to convince myself to back to 4.10. I don't like walking away from problems either. I am ok saying it's too big for me to fix and I need more help or that it would be too expensive and it's wiser to walk away or attempt a compromise, but I hate not having tried my best.

I agree. I don't think there be one "be all, tell all" solution for all of us having these problems. My case is a prime example. I don't see a lot of 231/5speed jeepers having these vibes post re-gear.

Totally agree. Each Jeep is indeed different and there is no universal solution. I'm just pointing out that there are more things to check that people may not have thought of.

I hope you guys can figure it out. I'm 2 years and counting and nowhere closer to solving it. I'm not giving up though. I have a trickle of hope that Tom Woods may find something with my front DS, and now that I'm driving without it, I will play with rear pinion angles some more to try and remedy the harmonic.

I'm very eager to see you proclaim "Guys, it's fixed. Here's what I did.". Seriously. It's frustrating to read thread after thread with no resolution. Keep us posted @bobthetj03.

 

[Chris]

It's difficult to diagnose yours as well, because you don't know what Dave is trying and what he isn't trying. You're sort of just left here with all these potential solutions you'd like to try, but you don't know if he's trying them or not.

Being as though Dave is a smart guy though, I have to imagine he's tried a lot more than we think he has.

 

[Cudabnu]

I just replaced my motor with a lower mileage motor. I have the OME Ultimate lift kit (haven't done a gear swap yet, but it is next) I have the Brown Dog MML. The car runs smooth 1st and 2nd, but I can feel a slight vibration in 3rd and 4th. I'm wondering since there is adjustments that can be made on the motor mounts if the engine isn't exactly aligned and made its twisting the Transfer Case enough left to right to cause this, and is it possible that re-gear may amplify this?

Just a thought...

 

[bobthetj03]

I've read scenarios where a MML has brought on certain unsavory characteristics. Changing the COG of the drivetrain on an already sensitive platform wouldn't be out of the realm.

 

[Chris]

Maybe the lesson here is that we should all just leave our TJs alone and keep them stock :risas3:

 

[Cudabnu]

I've read scenarios where a MML has brought on certain unsavory characteristics. Changing the COG of the drivetrain on an already sensitive platform wouldn't be out of the realm.

I had no vibrations before I swapped the motor (MML was on the orig motor and did not notice the vibes)
I'll have to loosen up the mounts and play around with it and see what happens

 

[ElectricWizard]

Maybe the lesson here is that we should all just leave our TJs alone and keep them stock :risas3:

But chasing down issues is half the reason to own a Jeep, isn't it?

 

[tworley]

Maybe the lesson here is that we should all just leave our TJs alone and keep them stock :risas3:

My dad always said "they came that way from the factory for a reason". Maybe hes on to something!

 

[psrivats]

It's difficult to diagnose yours as well, because you don't know what Dave is trying and what he isn't trying. You're sort of just left here with all these potential solutions you'd like to try, but you don't know if he's trying them or not.

Being as though Dave is a smart guy though, I have to imagine he's tried a lot more than we think he has.

Exactly. That's what is killing me. I don't want to pester him with questions but I also don't want to be left in the dark. I'm hoping that he's trying different things and none have worked so far, hence the silence. Here's already ruled out drive shafts and pinion angles. I'm willing to wait a couple more weeks perhaps, but after that I gotta do something.

 

[psrivats]

But chasing down issues is half the reason to own a Jeep, isn't it?

:risas3:

"That feeling you get .. only in a Jeep" makes more sense now (click the link!)

 

[StG58]

Here ya go @psrivats, no harmonic balancer.

Remember that this is about as far away as you can get from a Rubicon though. '99 SE. Manual transmission. No drive train mods. Very small lift.

 

[Chris]

My dad always said "they came that way from the factory for a reason". Maybe hes on to something!

My Dad always used to say, "If it ain't broke, don't fix it!".

I guess he has a point!

Exactly. That's what is killing me. I don't want to pester him with questions but I also don't want to be left in the dark. I'm hoping that he's trying different things and none have worked so far, hence the silence. Here's already ruled out drive shafts and pinion angles. I'm willing to wait a couple more weeks perhaps, but after that I gotta do something.

I don't blame you at all. I know of two reputable places in Salem at least that do almost exclusively modified Jeeps. I suppose you could always have one of them look at it for a second opinion. You never know... Sometimes second opinions really can help!

 

[psrivats]

Here ya go @psrivats, no harmonic balancer.
View attachment 61279
Remember that this is about as far away as you can get from a Rubicon though. '99 SE. Manual transmission. No drive train mods. Very small lift.

@StG58 thank you. REALLY interesting. So there are TJs without the balancer from the factory. What's the part at the end of the boot? Any idea?

The mystery deepens ...

 

[Chris]

The mystery deepens indeed! Why would some of them have harmonic balancers and some not?

There has to be more to it. Like perhaps certain gear / transmission combos they included the harmonic balancer, and maybe other combos didn't?

 

[psrivats]

The mystery deepens indeed! Why would some of them have harmonic balancers and some not?

There has to be more to it. Like perhaps certain gear / transmission combos they included the harmonic balancer, and maybe other combos didn't?

That's a very good model Chris, that would makes sense. I'm guessing Jeeps with 3.07s did not come with one perhaps?

 

[ElectricWizard]

@StG58 thank you. REALLY interesting. So there are TJs without the balancer from the factory. What's the part at the end of the boot? Any idea?

The mystery deepens ...

That is interesting. I had one but I've got an NV3550, I wonder if there's a difference with harmonic vibes?

I think that part is some sort of seal/oil slinger. I've seen it mentioned on videos when I was researching doing my SYE.

EDIT: I just noticed your post above regarding the gearing, that's not strictly the case since mine had 3.07 from the factory.

 

[StG58]

@StG58 thank you. REALLY interesting. So there are TJs without the balancer from the factory. What's the part at the end of the boot? Any idea?

The mystery deepens ...

I believe it's a mud slinger. I'm sure there's a more technical name for it though. It keeps water and debris out of the seal. It's pretty common because it's cheap and effective.

 

[psrivats]

I believe it's a mud slinger. I'm sure there's a more technical name for it though. It keeps water and debris out of the seal. It's pretty common because it's cheap and effective.

So we have two Jeeps with 3.07s, one without the balancer and one with. Both manuals. This tells me that this balancer was actually well thought out and only went out on certain combinations. I hope they did not slap it on on individual Jeep basis after some testing or something (likely not, given the volume sold).

What transmission you have in your Jeep @StG58 ?

 

[StG58]

So we have two Jeeps with 3.07s, one without the balancer and one with. Both manuals. This tells me that this balancer was actually well thought out and only went out on certain combinations. I hope they did not slap it on on individual Jeep basis after some testing or something (likely not, given the volume sold).

What transmission you have in your Jeep @StG58 ?

AX5 manual.

It's interesting that the four banger, with inherently more vibration than a six, and an AX5 transmission which is less stiff than the transmissions behind the six didn't get a harmonic balancer. The rest of the drive train is essentially the same except for minor details. The rest of the Jeep is essentially the same as well.