cpwolf

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Keep in mind that drivetrain vibrations are usually caused by the u-joints themselves vibrating/shaking from working into an excessive angle. That type of vibration can't just be lived with as it can take out the u-joints and possibly the adjacent seals on the axle and tcase too.

I agree with this, not that you need my agreement, ha.

But, putting up with vibes will rattle critical components, cause leaks and who knows what
 
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JMT

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And what, exactly is premature by your estimation?

What “I could tell”.

Never changed anything on that shaft for 3 years on a rig with 46,000 mi to 72,000 mi. The vibes were only under heavy load, so only on steep hills for me, which was a 200 foot section of driveway for me, never felt them in any other driving surface, so that’s my context. If that is what the OP is experiencing, and it sounds similar, it’s probably a non-issue (“lasts only a second”). Add 1 washer and it probably go away. It’s that slight.
 
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JMT

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I agree with this, not that you need my agreement, ha.

But, putting up with vibes will rattle critical components, cause leaks and who knows what

That’s true, just not what the OP is experiencing. “Lasts a second.” A second. How many seconds does he drive? A second of vibration at heavy torque starts is a very tiny portion of the time he drives, and the wearability will correspond.
 

Mike_H

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What “I could tell”.

Never changed anything on that shaft for 3 years on a rig with 46,000 mi to 72,000 mi. The vibes are only under heavy load, so only on steep hills for me, which was a 200 foot section of driveway for me, never felt them in any other driving surface, so that’s my context. If that is what the OP is experiencing, and it sounds similar, it’s probably a non-issue (“lasts only a second”). Add 1 washer and it probably go away. It’s that slight.

I only ask because I changed my original u-joints at 14 years old and 126,000 miles and they still weren't bad...so they have a MUCH longer life than we might think.
 
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JMT

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I only ask because I changed my original u-joints at 14 years old and 126,000 miles and they still weren't bad...so they have a MUCH longer life than we might think.

Good point. Last I looked 100,000 miles was life expectancy of a u-joint in the driveline. They are a very resilient part.

I've been wondering about ball joint life expectancy. My ball joints are still good at 102,000 miles, and I've been running bigger tires the last 32,000 miles.
 

Hi-Desert

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I believe the OP noted in a past post that he installed a UCF skid plate. This was not listed in the build data. I do not know how much that raises the transfer case, but that would increase the drive line angle.
 

Talltj

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From what I have read on the forum here, the 2.5” lift can cause vibes and varies from TJ to TJ. The problem I am currently having is a shudder/vibration that lasts only a second from a hard acceleration. Smooth acceleration appears to be fine. That being said, I am 90% sure that my issue will be resolved with a SYE and CV/DC Driveshaft install. My theory is that since the angle difference is so small that when accelerating hard, the resulting torque twists the rear axle slightly, causing the momentary shudder. For reference, I have:

OME 2” HD lift kit (Which I have read on here is actually 2.5”)

— 1.25 Savvy Body lift

— 1" JKS Aluminum Motor Mounts

— 33" BFG K02s

— 5.13 Gearing

I would rather spend the money on a SYE install than do a Tcase drop, but what do you guys think? Would not doing this cause any damage long term?

Honestly I'm not totally sold that, that is the issue as it is at a hard start only. Driveline alignment vibration issues usually happen at a higher drivshaft rpm (different rpm range for everyone depending on setup) but not usually launching from a stopped position. I would do as others have said and use washer to test it first dropping the T-case. I have a feeling you might find it to be something else. Since TJ's don't have leafspring suspension you should have no axle wrap and if you do then that's the first problem to repair. I would also examine your U-joints, T-case mounts and trany mounts and even motor mounts (even if they are aftermarket mounts the have replaced the OEM mounts). I would also look at the OEM slip yoke housing as these have been known to wear over time and can cause a vibration. If the last item is the case then I would move forward with an SYE or SSYE. I personally prefer the Teraflex SSYE it is cost effective and an easy install.
 
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ThomasFletch

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Wut.

With the rear driveshaft out, and the Jeep in 4 hi, it should have no problem driving. If it's not moving and the tires aren't resting on a frictionless plane, something else is wonky (like t case isn't getting into gear).
I read that as “front tires don’t pull hard enough to recreate it the vibe” not that they didn’t pull at all.
That is what I meant, yes. Sorry for not being clear! When I tried to do it, my front tires spun in place before moving me.

Another thing to consider is the health of the u joints.
As for the U-joints, I believe I replaced them about 5k – 10k miles ago? When I got the Jeep, it was about ~120k miles on it, and as of now I'm just shy of 150k. So, they shouldn't be that old yet. Now, as for the quality of the installation, that might be a different question. I'm very new to Jeeps/cars/trucks, let alone mechanical work in general, so I've been learning as I go. From what I can tell, they seem to be fine, no play or leaking or anything when I checked them.

I had that shuddering vibration under load for years at 2-2.5” suspension lift. Didn’t cause any premature wear of components that I could tell. Eventually moved on to bigger lift and SYE. Smooth as glass. Now I have the same shudder on another 2” rig. I’m not worried about it.
This is what everyone around me is telling me to do, just ignore/stop worrying. I'm pretty confident that it's been like this since I installed the lift about 2 years ago, but I'm just paranoid. I recently had my front U-joints on the front driveshaft explode on the freeway, but I'm pretty sure it was due to a bad U-ball joint that I hammered in too tight.

Keep in mind that drivetrain vibrations are usually caused by the u-joints themselves vibrating/shaking from working into an excessive angle. That type of vibration can't just be lived with as it can take out the u-joints and possibly the adjacent seals on the axle and tcase too.
I agree with this, not that you need my agreement, ha.

But, putting up with vibes will rattle critical components, cause leaks and who knows what
This is where my main concern lies. It's gotten to the point where I am checking to make sure that my driveshafts are on the right way; I even turned it around because of the vibrations at 70mph that I had. When I test drove it, I think it was better, but to be honest, I'm not quite sure what I should be feeling/looking for. At this point, every shake, shudder, or vibration I feel down the road I wonder if it is a result of the driveshaft.

That’s true, just not what the OP is experiencing. “Lasts a second.” A second. How many seconds does he drive? A second of vibration at heavy torque starts is a very tiny portion of the time he drives, and the wearability will correspond.
Correct. The only time I ever feel it is: if I let off the gas when getting onto my driveway and then accelerate up it slowly (I can try to get a video if not clear), on a heavy acceleration, as in an impatient jump off the line, or foot to the floor. I would think most would say: “Just don't do that” which they are probably right, but I am a dumb 23 year old who likes to pretend my Jeep can get off the line fast to then been dusted my friend's Corolla.

Honestly I'm not totally sold that, that is the issue as it is at a hard start only. Driveline alignment vibration issues usually happen at a higher drivshaft rpm (different rpm range for everyone depending on setup) but not usually launching from a stopped position. I would do as others have said and use washer to test it first dropping the T-case. I have a feeling you might find it to be something else. Since TJ's don't have leafspring suspension you should have no axle wrap and if you do then that's the first problem to repair. I would also examine your U-joints, T-case mounts and trany mounts and even motor mounts (even if they are aftermarket mounts the have replaced the OEM mounts). I would also look at the OEM slip yoke housing as these have been known to wear over time and can cause a vibration. If the last item is the case then I would move forward with an SYE or SSYE. I personally prefer the Teraflex SSYE it is cost effective and an easy install.
What would I be looking for with axle wrap? I'll double-check the motor mounts, and I just replaced the transfer case mount with a Mopar one from Rock Auto, but I will double check it. As for the transmission mounts, aren't they the same as the transfer case one, or does it have its own set of them?
When you say slip yoke housing, do you mean for the axle, transfer case, or both? What should I look for? I'm not sold on the SSYE as I don't plan on going any higher than I am now, so I don't think I would need it. Unless at this height, it has a major advantage over the regular SYE.

I believe the OP noted in a past post that he installed a UCF skid plate. This was not listed in the build data. I do not know how much that raises the transfer case, but that would increase the drive line angle.
Depends which skid he installed...UCF makes three different heights
You guys are always catching me slacking! Here is the skid-plate I purchased. I don't think it changes the drive line at all. The reason I got it was due to the front driveshaft rubbing on the transmission skid plate thing in the at certain articulations.


I know I say it in every post I make, but I really want to thank you guys for all the input and advice. Like I said, I'm still really new to all this, and this forum has not disappointed me with a lack of help/information. At times, it's almost an information overload for someone like me. I'll head to Home Depot to get everything to diagnose.
 
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tworley

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When I think of shudder I think of movement and not vibrations. How is the trans mount? Has it been looked at?
 
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freedom_in_4low

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That is what I meant, yes. Sorry for not being clear! When I tried to do it, my front tires spun in place before moving me.

still makes no sense. If the case is in 4wd and the rear driveshaft is out, it's just like any front wheel drive vehicle and should not be unable to move. You shouldn't even really notice anything is different except sharp turns where you'll feel some pulling in the steering wheel.
 

Talltj

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Honestly I'm not totally sold that, that is the issue as it is at a hard start only. Driveline alignment vibration issues usually happen at a higher drivshaft rpm (different rpm range for everyone depending on setup) but not usually launching from a stopped position. I would do as others have said and use washer to test it first dropping the T-case. I have a feeling you might find it to be something else. Since TJ's don't have leafspring suspension you should have no axle wrap and if you do then that's the first problem to repair. I would also examine your U-joints, T-case mounts and trany mounts and even motor mounts (even if they are aftermarket mounts the have replaced the OEM mounts). I would also look at the OEM slip yoke housing as these have been known to wear over time and can cause a vibration. If the last item is the case then I would move forward with an SYE or SSYE. I personally prefer the Teraflex SSYE it is cost effective and an easy install.

Honestly I'm not totally sold that, that is the issue as it is at a hard start only. Driveline alignment vibration issues usually happen at a higher drivshaft rpm (different rpm range for everyone depending on setup) but not usually launching from a stopped position. I would do as others have said and use washer to test it first dropping the T-case. I have a feeling you might find it to be something else. Since TJ's don't have leafspring suspension you should have no axle wrap and if you do then that's the first problem to repair. I would also examine your U-joints, T-case mounts and trany mounts and even motor mounts (even if they are aftermarket mounts the have replaced the OEM mounts). I would also look at the OEM slip yoke housing as these have been known to wear over time and can cause a vibration. If the last item is the case then I would move forward with an SYE or SSYE. I personally prefer the Teraflex SSYE it is cost effective and an easy install.

I mentioned axle wrap because you said something about the axle pinion alignment moving up and down due to torque. This would be axle wrap and and should not be possible with a TJ's suspension. If you have this kind of movement then something is broken or severely worn out.
 
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ThomasFletch

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Ok, I have returned with some data.
When I think of shudder I think of movement and not vibrations. How is the trans mount? Has it been looked at?

I just replaced the transmission mount with a new one from Rock Auto, at the beginning of October.

First off, I took out the driveshaft, to inspect the U-joints.
20221113_152911.jpg

20221113_152916.jpg

20221113_152925.jpg

20221113_152933.jpg

20221113_152942.jpg
I didn't see anything that look like marks, damage or wear, as I just simulated the rumble right before removing it. The only thing I might think that could be a mark is on the last picture, on the left. The slight dark mark, possibly?
What I did find interesting was the slip yoke (I think is what it is) itself.
20221113_153015.jpg
I found it a bit strange that the marking seemed to be at an angle. Could this mean it is shifting while rotating? Maybe the yoke is in fully, and then the shudder is it moving? I'm not sure, I just found it weird.

Here is the pinon angle without any spacers.
20221113_172902.jpg




20221113_152435.jpg

20221113_152438[1].jpg


20221113_171600.jpg
Here is the spacing I got with the correlating pinon angle. For some reason, whether it be user error, device error, etc., the angle didn't change with or without the spacers. I was able to recreate the shudder with the spacers on as well.


Lastly, I wanted to be clear on what I meant by not being able to get any traction without the rear drive shaft and in 4wd, so I took this video. So, it moves, just not quickly enough to generate the same force as if I were in RWD.



Please let me know what you guys think.
 

DrDmoney

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Ok, I have returned with some data.


I just replaced the transmission mount with a new one from Rock Auto, at the beginning of October.

First off, I took out the driveshaft, to inspect the U-joints.
View attachment 376597

View attachment 376598

View attachment 376599

View attachment 376600

View attachment 376601
I didn't see anything that look like marks, damage or wear, as I just simulated the rumble right before removing it. The only thing I might think that could be a mark is on the last picture, on the left. The slight dark mark, possibly?
What I did find interesting was the slip yoke (I think is what it is) itself.
View attachment 376602
I found it a bit strange that the marking seemed to be at an angle. Could this mean it is shifting while rotating? Maybe the yoke is in fully, and then the shudder is it moving? I'm not sure, I just found it weird.

Here is the pinon angle without any spacers.
View attachment 376603




View attachment 376595

View attachment 376593

View attachment 376596
Here is the spacing I got with the correlating pinon angle. For some reason, whether it be user error, device error, etc., the angle didn't change with or without the spacers. I was able to recreate the shudder with the spacers on as well.


Lastly, I wanted to be clear on what I meant by not being able to get any traction without the rear drive shaft and in 4wd, so I took this video. So, it moves, just not quickly enough to generate the same force as if I were in RWD.

View attachment 376606

Please let me know what you guys think.

The pinion angle is not changed by the spacers at the transfer case, the purpose of the spacers is to drop the output shaft down to better match the pinion angle. With your style of driveshaft they need to be at the same angle.
 

Jerry Bransford

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The pinion angle is not changed by the spacers at the transfer case, the purpose of the spacers is to drop the output shaft down to better match the pinion angle. With your style of driveshaft they need to be at the same angle.
X2, the pinion angle needs to stay parallel to the output shaft angle when you're still running the factory rear driveshaft. Like this...

2joint_angle2.png


The rear pinion angle should not be changed when the factory driveshaft is still installed
 
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ThomasFletch

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The pinion angle is not changed by the spacers at the transfer case, the purpose of the spacers is to drop the output shaft down to better match the pinion angle. With your style of driveshaft they need to be at the same angle.
X2, the pinion angle needs to stay parallel to the output shaft angle when you're still running the factory rear driveshaft. Like this...

View attachment 376633

The rear pinion angle should not be changed when the factory driveshaft is still installed
Gotcha. So, I'm assuming that means there wasn't enough spacing to match the transfer case to the pinion angle?

How much slip yoke engagement do you have?
I'm not sure what this means. What should I check/look for?