Help with vibration felt in seat

jxv1247

jxv1247

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Bedford, New York
Been researching and trying numerous solutions to solve a vibration I have in the rear end of the jeep, it can be felt in my seat from 50-63 or so mph, after that it either fades out or isn't as noticeable. I have played with pinion angle in the rear anywhere from -2 to +1 and no change, I have gotten the tires balanced twice in the past week and hasn't changed the vibration. Rear driveshaft is an Adams that is less than a week old, front is stock. There is no change if I remove the front driveshaft. Motor mounts and trans mounts are new. There's no play at the pinion in the rear, the SYE output may have the slightest movement that can be seen when really pushing down and up at the edge of the seal (If I had to guess 0.2mm). The vibration is pretty aggressive and nothing is jumping out as being super loose or very wrong . Im stumped at where else to look.

Edit : Forgot to add, vibration still happens in neutral coasting at that speed
 
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So you’re saying you have a SYE.

Do you have adjustable control arms, a Double Cardan Drive Shaft?

When messing with pinion angle…that should be set by pointing the Yoke at the TC output.

You said you pulled the front DS, have you pulled the rear drive shaft and seen if you get the vibes?
 
cpwolf said:
So you’re saying you have a SYE.

Do you have adjustable control arms, a Double Cardan Drive Shaft?

When messing with pinion angle…that should be set by pointing the Yoke at the TC output.

You said you pulled the front DS, have you pulled the rear drive shaft and seen if you get the vibes?
Click to expand...

Yes, I have a SYE. Rear is a brand new adams double cardan shaft, before then I had a tom woods Dc shaft. Pinon angle is sitting at 0.8 degrees down at the moment. I have not pulled the rear shaft due to having a lunch box locker in the front.
 
jxv1247 said:
Yes, I have a SYE. Rear is a brand new adams double cardan shaft, before then I had a tom woods Dc shaft. Pinon angle is sitting at 0.8 degrees down at the moment. I have not pulled the rear shaft due to having a lunch box locker in the front.
Click to expand...

Personally I would prefer the build of the TW driveshaft over the Adams driveshaft.
Who is the maker of the SYE ?
With .8* down that should be sufficient to negate any vibrations when torqued is applied to the driveshaft under acceleration.
Since the vibrations are also felt in neutral coasting; have you verified the nut holding the yoke onto the transfercase output shaft is torqued properly and is the flat washer present to distribute the torque force on the nut on to the yoke?
 
CharlesHS said:
Personally I would prefer the build of the TW driveshaft over the Adams driveshaft.
Who is the maker of the SYE ?
With .8* down that should be sufficient to negate any vibrations when torqued is applied to the driveshaft under acceleration.
Since the vibrations are also felt in neutral coasting; have you verified the nut holding the yoke onto the transfercase output shaft is torqued properly and is the flat washer present to distribute the torque force on the nut on to the yoke?
Click to expand...

It's an Advance Adapters SYE. I actually did check that this morning because I thought there was a possibility the washer was gone or there yoke was loose which it was not,
 
The only other suggestion I would have which is what was previously suggested would be to remove the rear driveshaft and verify the vibrations are gone or still present.
Why did you replace the TW driveshaft ?
Is the TW driveshaft still usable ?
IF the TW driveshaft is still usable; I would remove the Adams and install the TW to see if the vibrations are better, worse or same.
 
CharlesHS said:
The only other suggestion I would have which is what was previously suggested would be to remove the rear driveshaft and verify the vibrations are gone or still present.
Why did you replace the TW driveshaft ?
Is the TW driveshaft still usable ?
IF the TW driveshaft is still usable I would swap the TW with the Adams to see if the vibrations are better, worse or same.
Click to expand...

The TW driveshaft unfortunately developed quite a bit of play at the splines, not sure if it was neglect from the previous owner or not.
 
jxv1247 said:
The TW driveshaft unfortunately developed quite a bit of play at the splines, not sure if it was neglect from the previous owner or not.
Click to expand...

What is the condition of the yokes U joints cup seating areas for the transfercase and rear differential yokes ?
Is there any damage to the outer area of the yokes or burrs which do not allow the cups to seat properly ?
Are the tabs on the yokes that hold the U joint cups in place still there or damaged ?
 
CharlesHS said:
What is the condition of the U joints cup seating areas on the transfercase and rear differential yokes ?
Is there any damage to the outer area of the yokes or burrs which do not allow the cups to seat properly ?
Click to expand...

Diff yoke is in good shape, T case yoke I believe was good , I will take a look at it again tomorrow. No burrs.
 
I had a Mustang many years ago. I would get horrible vibration at highway speeds. A mechanic told me that my drive shaft needed to be balanced. He balanced it and my Mustang drove so smoothly, it was like riding on air at highway speeds. The downside is that I blew my heads at over 100mph. That was my youth. Fast forward. I had similar vibration problems with my Wrangler at 60-65mph, ever since it was new. Everyone said the problem was a wheel balance problem. So, I took my Wrangler back to the tire shop to have the tires balanced again. The problem persisted. Eventually, I brought new tires, and had them balanced at a higher rated shop. Now, my Jeep can do 80 to 90 mph, without any vibration. It is like driving on air again at highway speeds. I was so happy and then realized that I never want to drive above 70mph anyway. Although at times, it drives so smooth that I'll look down at my speedo, and it has gone above 80mph. Oops. I don't want a ticket, nor do I want to risk shortening my engine life, so I back off down to 65 or 70, and I just try to stay in the slow lane. So, maybe you need to find a high rated tire shop on Google in your area, and take it there to have your tires properly balanced. Even the dealership didn't seem to get it right.
 
jxv1247 said:
The TW driveshaft unfortunately developed quite a bit of play at the splines, not sure if it was neglect from the previous owner or not.
Click to expand...

I would have contacted TW, Shawn emails back quickly, and seen if that can be corrected. That’s just me, because I know he would help me chase any vibe.

I would still pull the rear DS, drive 4H. Just stay off the accelerator in turns. Go get on the open road and see what it feels like.
 
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cpwolf said:
I would have contacted TW, Shawn emails back quickly, and seen if that can be corrected. That’s just me, because I know he would help me chase any vibe.

I would still pull the rear DS, drive 4H. Just stay off the accelerator in turns. Go get on the open road and see what it feels like.
Click to expand...

I’ll shoot a email over, wouldn’t hurt
 
Artsifrtsi said:
.8° down is not the same as pointing your pinion yoke at the transfer case output...
Click to expand...

Artsifrtsi said:
With the DC rear driveshaft and SYE, you point the pinion at the rear output of the transfer case.
Click to expand...


I think @jxv1247 is pointing it at the Output, but as I've seen some suggest, rather that exactly at the Output on the TC, some suggest a little (in this instance 0.8 degrees below) so that under load some have said the pinion will rotate up some. So it is set to what you're suggesting.



One question @jxv1247 or others that may have more experience, would it be worth rotating up that 0.8 to see if your TJ doesn't turn up like that at the speeds you're seeing vibrations? If you pull the DS, and it is indeed vibes gone, then you know you're looking at the DS. So, maybe rotate up some. Just things that would go through my mind to eliminate as possible reasons that are just turning a few wrenches and control arms.
 
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