Re-geared, now I have a vibration above 50 mph

S.McArthur

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As expected, squared the axle and the violent vibration went away. I still have a light vibration that is first noticeable at 50, it gets more noticeable as speed picks up; at 70, it’s noticeable but tolerant.
5.13s are fun now
 
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TheWicked

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Are all of you guys using leveling pucks too?

I have an 06 LJ 6 speed. Got it with like 68,000 miles. It had a 4" RC lift, transfer case drop, junk Falken Wildpeaks and it did not shimmy, shake, or harmonically vibrate. It had aftermarket bumpers.

The front wasn't level with the back. I put a winch on and the front was sagging even more so I bought Currie 4" springs, the ones with "extra 1" of height is necessary to compensate for heavy winches, bumpers, etc ". Looking back that statement applied to JK's but whatever. Shocks broke taking them off so I replaced them too.

Still wasn't level. Still no shimmy or wobble or anything like that. A few months later I put on 1" poly spacers to level it out. I think the front was like 3/4" lower than the back. That unleashed hell. Death wobble, shimmy, all that. I took it in for an alignment and described everything. Naive me though I had effected caster that bad. The reputable 4x4 shop said the drag link was shot. Replaced that, alignment, balanced tires, said the shimmy was still there but not as bad. Said the tires were to blame at this point.

Fast forward 6 months and I buy new wheels and tires (Mickey Thompson atz 33"). Get those put on and the same shake/shimmy was there. This is where I went down the rabbit hole.

I replaced everything. Ball joints, u joints, tie rod (zj conversion), wheel bearings, adjustable track bar. A lot of this stuff was either shot or close to it. Thought that would have nailed it but the shake was still there. I go full retard at this point and replace all 8 control arms with adjustable MC's, Tom W driveshaft, advance adapters SYE kit. Removed the transfer case drop. Replaced the transmission mount and the passenger side engine mount (I have the other one, just didn't do it yet, they didn't look too bad, although the TC drop had them all kinds of deformed). Set pinion angles. And while it rode better than it ever had there was still some shake (45-55mph).

I found out about MT's warranty and that if it takes more than 1% of the tire weight to balance them they can be replaced. Two had like 14-16 ounces of weight so the shop replaced them and re-balanced (road force) all the tires for free. They did an alignment too, although they didn't set all the control arms like I asked. They are double adjustable and when I installed them I set them to the length of the arms I was taking off.

I don't want to call it a shake but it's like a harmonic, just like everyone is talking about in this thread. I have not re geared from the 3.73 that it came with. Going down a hill at like 55, in neutral, the gear shift and steering wheel both have the same ~55hz vibration. The wheel moves a little but not a full fledged shake. It changes depending on the day, the road, temperature, and psi.

I'm in the middle of trying to fix that now. I'm not convinced that my axles are where they could optimally be. The MC instructions would have had me put the arms longer than the ones I was replacing. But doing them one at a time like I did I didn't have much of an option.

But back to the pucks, are all you guys using something like that to level your jeeps? I can't say I had an issue before them. I thought about taking them off but these springs are super long and I hate using spring compressors. Could a (near) level jeep be more problematic that one with a lower front?

Also, I have a mountain bike with big fat tires. I get the same kind of up and down oscillation on the street. In that case it's 100% from tires.
 

JMT

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Are all of you guys using leveling pucks too?

I have an 06 LJ 6 speed. Got it with like 68,000 miles. It had a 4" RC lift, transfer case drop, junk Falken Wildpeaks and it did not shimmy, shake, or harmonically vibrate. It had aftermarket bumpers.

The front wasn't level with the back. I put a winch on and the front was sagging even more so I bought Currie 4" springs, the ones with "extra 1" of height is necessary to compensate for heavy winches, bumpers, etc ". Looking back that statement applied to JK's but whatever. Shocks broke taking them off so I replaced them too.

Still wasn't level. Still no shimmy or wobble or anything like that. A few months later I put on 1" poly spacers to level it out. I think the front was like 3/4" lower than the back. That unleashed hell. Death wobble, shimmy, all that. I took it in for an alignment and described everything. Naive me though I had effected caster that bad. The reputable 4x4 shop said the drag link was shot. Replaced that, alignment, balanced tires, said the shimmy was still there but not as bad. Said the tires were to blame at this point.

Fast forward 6 months and I buy new wheels and tires (Mickey Thompson atz 33"). Get those put on and the same shake/shimmy was there. This is where I went down the rabbit hole.

I replaced everything. Ball joints, u joints, tie rod (zj conversion), wheel bearings, adjustable track bar. A lot of this stuff was either shot or close to it. Thought that would have nailed it but the shake was still there. I go full retard at this point and replace all 8 control arms with adjustable MC's, Tom W driveshaft, advance adapters SYE kit. Removed the transfer case drop. Replaced the transmission mount and the passenger side engine mount (I have the other one, just didn't do it yet, they didn't look too bad, although the TC drop had them all kinds of deformed). Set pinion angles. And while it rode better than it ever had there was still some shake (45-55mph).

I found out about MT's warranty and that if it takes more than 1% of the tire weight to balance them they can be replaced. Two had like 14-16 ounces of weight so the shop replaced them and re-balanced (road force) all the tires for free. They did an alignment too, although they didn't set all the control arms like I asked. They are double adjustable and when I installed them I set them to the length of the arms I was taking off.

I don't want to call it a shake but it's like a harmonic, just like everyone is talking about in this thread. I have not re geared from the 3.73 that it came with. Going down a hill at like 55, in neutral, the gear shift and steering wheel both have the same ~55hz vibration. The wheel moves a little but not a full fledged shake. It changes depending on the day, the road, temperature, and psi.

I'm in the middle of trying to fix that now. I'm not convinced that my axles are where they could optimally be. The MC instructions would have had me put the arms longer than the ones I was replacing. But doing them one at a time like I did I didn't have much of an option.

But back to the pucks, are all you guys using something like that to level your jeeps? I can't say I had an issue before them. I thought about taking them off but these springs are super long and I hate using spring compressors. Could a (near) level jeep be more problematic that one with a lower front?

Also, I have a mountain bike with big fat tires. I get the same kind of up and down oscillation on the street. In that case it's 100% from tires.
Whew...I read all that fiasco.

To answer your question directly, yes, I am using leveling pucks, yes I had DW, but not due to pucks. I have never seen that cause in the 2+ years I’ve been on the forum. I’ve never seen harmonic vibes as a result either.

You solved DW and now have harmonics. Only solution I’ve seen is hubs. I have seen harmonics lessen with a different TCase skid and soundproofing the tub
 

glwood

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Are all of you guys using leveling pucks too?

I have an 06 LJ 6 speed. Got it with like 68,000 miles. It had a 4" RC lift, transfer case drop, junk Falken Wildpeaks and it did not shimmy, shake, or harmonically vibrate. It had aftermarket bumpers.

The front wasn't level with the back. I put a winch on and the front was sagging even more so I bought Currie 4" springs, the ones with "extra 1" of height is necessary to compensate for heavy winches, bumpers, etc ". Looking back that statement applied to JK's but whatever. Shocks broke taking them off so I replaced them too.

Still wasn't level. Still no shimmy or wobble or anything like that. A few months later I put on 1" poly spacers to level it out. I think the front was like 3/4" lower than the back. That unleashed hell. Death wobble, shimmy, all that. I took it in for an alignment and described everything. Naive me though I had effected caster that bad. The reputable 4x4 shop said the drag link was shot. Replaced that, alignment, balanced tires, said the shimmy was still there but not as bad. Said the tires were to blame at this point.

Fast forward 6 months and I buy new wheels and tires (Mickey Thompson atz 33"). Get those put on and the same shake/shimmy was there. This is where I went down the rabbit hole.

I replaced everything. Ball joints, u joints, tie rod (zj conversion), wheel bearings, adjustable track bar. A lot of this stuff was either shot or close to it. Thought that would have nailed it but the shake was still there. I go full retard at this point and replace all 8 control arms with adjustable MC's, Tom W driveshaft, advance adapters SYE kit. Removed the transfer case drop. Replaced the transmission mount and the passenger side engine mount (I have the other one, just didn't do it yet, they didn't look too bad, although the TC drop had them all kinds of deformed). Set pinion angles. And while it rode better than it ever had there was still some shake (45-55mph).

I found out about MT's warranty and that if it takes more than 1% of the tire weight to balance them they can be replaced. Two had like 14-16 ounces of weight so the shop replaced them and re-balanced (road force) all the tires for free. They did an alignment too, although they didn't set all the control arms like I asked. They are double adjustable and when I installed them I set them to the length of the arms I was taking off.

I don't want to call it a shake but it's like a harmonic, just like everyone is talking about in this thread. I have not re geared from the 3.73 that it came with. Going down a hill at like 55, in neutral, the gear shift and steering wheel both have the same ~55hz vibration. The wheel moves a little but not a full fledged shake. It changes depending on the day, the road, temperature, and psi.

I'm in the middle of trying to fix that now. I'm not convinced that my axles are where they could optimally be. The MC instructions would have had me put the arms longer than the ones I was replacing. But doing them one at a time like I did I didn't have much of an option.

But back to the pucks, are all you guys using something like that to level your jeeps? I can't say I had an issue before them. I thought about taking them off but these springs are super long and I hate using spring compressors. Could a (near) level jeep be more problematic that one with a lower front?

Also, I have a mountain bike with big fat tires. I get the same kind of up and down oscillation on the street. In that case it's 100% from tires.
Have you tried driving your Jeep with the front or rear drive shafts removed to see if that affects the harmonics?
 

TheWicked

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Feb 14, 2018
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Have you tried driving your Jeep with the front or rear drive shafts removed to see if that affects the harmonics?
I have not. I was going to check shaft runout too. But it doesn't seem like any of that really worked wonders for anyone else. I had planned on 35's and a regear eventually. But if it could make the harmonics worse I don't think I will. Also wanted to do the no body lift UCF low profile skid. Really since I just sunk all this money into the Jeep and I replaced one problem with another I don't know if I want to spend another dime on this thing.

Hell I was even considering selling the LJ and getting a JL Rubicon. But I'm reading people are having these same issues, brand new off the lot, during test drives, with no mods at all.
 
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bobthetj03

bobthetj03

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I have not. I was going to check shaft runout too. But it doesn't seem like any of that really worked wonders for anyone else. I had planned on 35's and a regear eventually. But if it could make the harmonics worse I don't think I will. Also wanted to do the no body lift UCF low profile skid. Really since I just sunk all this money into the Jeep and I replaced one problem with another I don't know if I want to spend another dime on this thing.

Hell I was even considering selling the LJ and getting a JL Rubicon. But I'm reading people are having these same issues, brand new off the lot, during test drives, with no mods at all.
Like you, I've pretty much went thru the replace everything gambit. I still have a harmonic above 55 mph, but it is hard to detect with the hard top off due to all the other noises related to top off driving. I too am running 0.75" spring pucks, and sit just about level.
 

Mr. Bills

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FYI, I have also added poly lift spacers for leveling purposes. There was no change in harmonics or vibrations when the spacers were initially installed and no change when they were removed and replaced with spacers of slightly different lengths. The various spacers used while I was dialing in the desired rake have been 1.25", 1.75" and 2.0".

While I realize that the vibrations and/or harmonics seemed to develop when @TheWicked installed his 1" spacers, I am having a difficult time comprehending how the spacers themselves are contributing to his issues.
 

TheWicked

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While I realize that the vibrations and/or harmonics seemed to develop when @TheWicked installed his 1" spacers, I am having a difficult time comprehending how the spacers themselves are contributing to his issues.
Someone in this thread mentioned the change in pinion angle based on how much weight was in the back and it's affect on the harmonics. That weight effects the stance too. The same could be true if the front of the vehicle is higher or lower because of worn springs or the use of pucks. Just a theory but it has to have effects on stance or aerodynamics.

I'd be curious if someone had the resources to have a 4" spring in the back and a 2" up front (drastic change) and if it effects harmonics.
 
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bobthetj03

bobthetj03

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In my case I think it came down to ujoint operating angles. I lowered the t-case skid down 0.75" and my physical vibes felt in the steering wheel/seat went away. Why some TJ's are more sensitive to that than others is a complete mystery to me. I ended up putting a 1" MML on and put the t-case back up where it belongs and netted the same results as lower the t-case skid down 0.75". Jury is still out on the harmonic. Oh, also worth mentioning, new tires cleared some of the 50-60 mph harmonic. My KM2's were pretty wore out.
 

TheWicked

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Please describe in some detail how you set your pinion angles just so there's no ambiguity.
A magnetic angle finder. After reading this thread I've yet to try and adjust the back down .5 or 1 and the front up. Right now the front was set for caster by the garage. Haven't checked to see what the angle is.

But I was zeroing the finder on the driveshaft then sticking it on the diff flat and adjusted to 90 (it's only magnetic on one side). And Like I said I haven't tried to adjust for axle roll or whatever it's called.
 

g.hayduke

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I've yet to try and adjust the back down .5 or 1 and the front up. Right now the front was set for caster by the garage.
Well, this is the #1 thing you should be focused on. You need to make sure your pinion angles are as close to correct as possible before looking at anything else. The general rule espoused by the experts here is that pinion angle takes priority over caster. It's generally not possible to get both pinion angle and caster correct. If the alignment shop set the caster to spec, the pinion angle is probably off enough to generate vibes. I think most end up with ~5 degrees of caster which is less than spec.

And since front is not generally under load at speed, just freewheeling on the road, I shoot for 0 degrees in the front which gives a better caster number than if it's pointed up slightly.
 

Alex01

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Someone in this thread mentioned the change in pinion angle based on how much weight was in the back and it's affect on the harmonics. That weight effects the stance too. The same could be true if the front of the vehicle is higher or lower because of worn springs or the use of pucks. Just a theory but it has to have effects on stance or aerodynamics.

I'd be curious if someone had the resources to have a 4" spring in the back and a 2" up front (drastic change) and if it effects harmonics.
I believe the person you are referring to is @tomtaylz and his LJR. His vibration issue was caused by the pinion angle. He also had a vibration at idle while under load that never got fully solved.
 

TheWicked

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Ok so here are my numbers.

Before adjustable control arms my caster was 6.8*. Before and after leveling pucks/springs. No idea about the drive line angles back then.

After adjustable control arms the caster was set to 7.0*. So currently the front axle is 3.5* below the front driveshaft. The rear driveshaft is totally perpendicular, 0.0*.
 
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bobthetj03

bobthetj03

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Adjust the front axle closer to the ds angle and test drive.
 

Mr. Bills

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Adjust the front axle closer to the ds angle and test drive.
X2.

I was able to dial out some of my post re-gear 68+ mph vibration/harmonic by doing this, i.e., front driveshaft angle = pinion angle, then raising the pinion angle by 0.5* increments until my steering "return to center" became too slow for my tastes (due to the reduction in caster), then backing off 0.25* and calling it a day. That was about as good as it was going to get (and the point when I decided to convert to manual hubs and be done with it).