Trouble with severe vibration 25-50 mph

Pert Near

Pert Near

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I've been chasing this since I bought the LJ last October. Any suggestions or recommendations would be greatly appreciated.
Actions taken...new tires, caster, pinon angle, upgraded to RPM drag link, track bar, and tie rod. The LJ drives better than when I bought it but still has a vibration under the drivers seat and dash from 25-50mph.
We did see that the harmonic balancer on the transfer case seems to be out of balance or not installed correctly.
 
Is your LJ lifted? Tummy tuck? This sounds like an incorrect rear pinion angle.

Have you tried removing the rear driveshaft and driving in 4high?
 
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deadbeat son said:
Have you tried removing the rear driveshaft and driving in 4high?

Likewise, have you tried driving with a disconnected front driveshaft?
Click to expand...

This, I would start here. Figure out which end is doing it.

If it's under your seat, I'm assuming with the Savvy skid you've got the trans mount good? That bracket can crack I thought I read, and I've seen some extra welding done. The bracket that bolts to the bottom of the transmission.
 
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deadbeat son said:
Have you tried removing the rear driveshaft and driving in 4high?

Likewise, have you tried driving with a disconnected front driveshaft?
Click to expand...

cpwolf said:
This, I would start here. Figure out which end is doing it.

If it's under your seat, I'm assuming with the Savvy skid you've got the trans mount good? That bracket can crack I thought I read, and I've seen some extra welding done. The bracket that bolts to the bottom of the transmission.
Click to expand...

Thanks for the advice! I'll report back. Cheers!
 
Pert Near said:
I've been chasing this since I bought the LJ last October. Any suggestions or recommendations would be greatly appreciated.
Actions taken...new tires, caster, pinon angle, upgraded to RPM drag link, track bar, and tie rod. The LJ drives better than when I bought it but still has a vibration under the drivers seat and dash from 25-50mph.
We did see that the harmonic balancer on the transfer case seems to be out of balance or not installed correctly.
Click to expand...

I don’t see how you would still have the rear balancer with a 4”lift and a tummy tuck. Surely you have a after market DC driveshaft and SYE
 
Last edited:
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I removed the rear drive shaft and the vibrations are gone. The driveshaft I have is a brand new Adams. This leads me to believe that my transfer case output shaft needs to be replaced or something is out of whack with the harmonic balancer.
Can I just replace the output shaft of a 241 J transfer case?
Also, can the harmonic balancer be removed?
 
Pert Near said:
I removed the rear drive shaft and the vibrations are gone. The driveshaft I have is a brand new Adams. This leads me to believe that my transfer case output shaft needs to be replaced or something is out of whack with the harmonic balancer.
Can I just replace the output shaft of a 241 J transfer case?
Also, can the harmonic balancer be removed?
Click to expand...

Are there vibes with the front shaft removed and only the rear installed? What we're trying to see is if the issue is definitely in your rear driveline or if it only occurs when both are in place. Knowing the answer to that may help you figure out your best solution.
 
Pert Near said:
I removed the rear drive shaft and the vibrations are gone. The driveshaft I have is a brand new Adams. This leads me to believe that my transfer case output shaft needs to be replaced or something is out of whack with the harmonic balancer.
Can I just replace the output shaft of a 241 J transfer case?
Also, can the harmonic balancer be removed?
Click to expand...

That's a good start. I would as mentioned, put the rear in place, and then pull the front shaft.

Can you post pics of that harmonic balancer, what you're seeing. In the original post, you stated that it seems to be out of balance...or not installed correctly? Must look really off. I would agree, that's where I would focus. I have a 231 and put a SS SYE on, and had to pull my Harmonic Balancer and shaft.
 
First the driveshaft in the rear can’t be to spec because there’s really not a spec once you’ve built a jeep- Whatever angle you need not to have vibrations is the correct angle.

Blaine recently explained this to me- His shop may be under one 50 or 60 times to dial in the pinion angle.

Aside from that you have something going on way out of whack - I’m hoping the rear is a CV shaft - You may have to do a video as you rotate and get on the phone with Adams.
 
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AndyG said:
First the driveshaft in the rear can’t be to spec because there’s really not a spec once you’ve built a jeep- Whatever angle you need not to have vibrations is the correct angle.

Blaine recently explained this to me- His shop may be under one 50 or 60 times to dial in the pinion angle.

Aside from that you have something going on way out of whack - I’m hoping the rear is a CV shaft - You may have to do a video as you rotate and get on the phone with Adams.
Click to expand...

One thing to check is to make sure the drive shaft is properly phased. If take the slip yoke apart is is possible to put it back together with the two yokes out of phase. The yoke in each end need to be exactly 90 degrees offset so that they each cancel each other out. If one end is exactly perpendicular the opposed end has to be exactly horizontal. I saw this on a friends Samari years ago when they were chasing a vibe all over the place. I will see if I can find a diagram.
 
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Sean B said:
One thing to check is to make sure the drive shaft is properly phased. If take the slip yoke apart is is possible to put it back together with the two yokes out of phase. The yoke in each end need to be exactly 90 degrees offset so that they each cancel each other out. If one end is exactly perpendicular the opposed end has to be exactly horizontal. I saw this on a friends Samari years ago when they were chasing a vibe all over the place. I will see if I can find a diagram.
Click to expand...

Had that once too- will shake your eye teeth out.

Good post.
 
AndyG said:
Had that once too- will shake your eye teeth out.

Good post.
Click to expand...

I explained this wrong, they need to be aligned, so the forces cancel each other out. I had to look at one to visualize it. I attached a pic.
ECB04537-DF97-4104-974E-1FDD31DE1F99.png
 
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cpwolf said:
He said it’s a new Adams shaft, I’d be shocked they messed that up, but it’s possible for sure.
Click to expand...

It would be odd but you never know. Always easier to figure something out if a problem happens after you do something.

I found a pic of one that has a double cardan joint.

B4D0F0D2-B848-4B16-922B-6434D46E3427.jpeg
 
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