Vibrations after re-gear

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Rex Baucom

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I had revolution 4.88 R and P set installed in the front and rear of my TJ. Also had a Detroit Trutrac and lockrite installed as well.
It's back on the road for about a week. Been running great.
Started to notice what I would call a rotational vibration at about 60 mph. It's not a consistent vibe but it almost comes and goes at a steady but not fast pace. Scares me because the vibe is slow enough that it wouldn't be the tires. As they are spinning way faster.

I do have an SYE and CV drive shaft and adjustable upper control arms. I also know that the the bigger gears and high rpm's some show drive line vibes that weren't there before.

Is what I describe more consistent with drive line vibes or could it be something else?? Like problem with gear set or tires??? I have not determined if it's the front or rear yet. I can feel it vibrating through the pedals and even the seat. Only at 60+ mph.

Thanks



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https://wranglertjforum.com/posts/84454/

I started this thread a while back with the same vibes after my re-gear. Still have the vibes and have just about replaced everything in the drive train sans the transmission and engine. Will be replacing my trany mount this weekend, then next the rear diff yoke. After that, I'm at a loss. Have you disconnected your front drive shaft yet to pinpoint if it's the front or rear? Mine is coming from the rear. @jeepndogs has a similar thread except his was coming from the front. His remedy was to install manual locking hubs up front so the driveshaft wasn't spinning anymore in 2wd. You're not the only one with this problem, so not sure what's happening only on certain TJ's.
 
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Disconnect your front driveshaft as @bobthetj03 suggested. Drive around like that and it should hopefully be able to pinpoint if it' coming from the front or the rear.

The only thing you did was new gears and a locket though? Nothing else occurred at the same time (i.e. new lift, new tires, etc.)?
 
bobthetj03 said:
https://wranglertjforum.com/posts/84454/

I started this thread a while back with the same vibes after my re-gear. Still have the vibes and have just about replaced everything in the drive train sans the transmission and engine. Will be replacing my trany mount this weekend, then next the rear diff yoke. After that, I'm at a loss. Have you disconnected your front drive shaft yet to pinpoint if it's the front or rear? Mine is coming from the rear. @jeepndogs has a similar thread except his was coming from the front. His remedy was to install manual locking hubs up front so the driveshaft wasn't spinning anymore in 2wd. You're not the only one with this problem, so not sure what's happening only on certain TJ's.
Click to expand...

Thanks for that link. I spent this morning looking for your thread and I couldn't find it either the search function on the app I use.

I'm going to diagnose wether it's the front or back over the weekend and I'm going to make sure my pinion angles are dead on.

Sounds like we have a common thing going on. How much are you driving your jeep and should I limit how much I drive it.

Have heard about re balancing the drive shaft?????

Thanks



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Chris said:
Disconnect your front driveshaft as @bobthetj03 suggested. Drive around like that and it should hopefully be able to pinpoint if it' coming from the front or the rear.

The only thing you did was new gears and a locket though? Nothing else occurred at the same time (i.e. new lift, new tires, etc.)?
Click to expand...

Will do!! Nope only gears and lockers. Break in procedure done exactly like said. Already had a 3.5" lift with SYE and no vibes. So this is a new thing that has started. I'm going to figure out which drive shaft and angles this weekend.



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Rex Baucom said:
Thanks for that link. I spent this morning looking for your thread and I couldn't find it either the search function on the app I use.

I'm going to diagnose wether it's the front or back over the weekend and I'm going to make sure my pinion angles are dead on.

Sounds like we have a common thing going on. How much are you driving your jeep and should I limit how much I drive it.

Have heard about re balancing the drive shaft?????

Thanks



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Click to expand...

After all the things I've done so far, I have minimized the vibes to a point that I can drive it safely IMO. It's my daily commuter, so I'm driving it and wheeling it. Right now with the top off I can't hear it as bad, but still feel the harmonic in my seat and the steering wheel just a tad. I've replaced the front drive shaft with a brand new one, twice, and just recently had the transfer case rebuilt and a AA SYE installed, so new rear CV driveshaft as well. The vibes got better after the SYE, but still there enough to be irritating above 50 mph. And, like you, my jeep drove vibe free until I did the re-gear, with nothing else being changed except for the replacement of a rear axle bearing/seal, and the only reason for that was the right rear seal was seeping a bit.
 
So, the driveshaft is spinning faster now and you could be feeling vibrations that did not appear at the previously slower speed.
Things to check are the obvious; u joints, mounts, etc. Be a good idea to check pinion angle as well. You can pull the front shaft and see if it is still there or goes away to pinpoint a specific shaft.

Just to point out: the driveshaft spins significantly faster than the tires, in case you didn't know. It also isn't likely a gear or set up issue. The diff would have to be just about falling apart to induce vibrations and there would be no mistaking that situation.
 
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Rob5589 said:
So, the driveshaft is spinning faster now and you could be feeling vibrations that did not appear at the previously slower speed.
Things to check are the obvious; u joints, mounts, etc. Be a good idea to check pinion angle as well. You can pull the front shaft and see if it is still there or goes away to pinpoint a specific shaft.

Just to point out: the driveshaft spins significantly faster than the tires, in case you didn't know. It also isn't likely a gear or set up issue. The diff would have to be just about falling apart to induce vibrations and there would be no mistaking that situation.
Click to expand...

Rear drive shaft is a new Adams drive shaft with new u joints. Everything associated with the front drive shaft is def stock and probably original.

I'm going to dive in this weekend and check it out. Good to know about the gear. The jeep drives great, the gear are probably fine and they are broken in very nice.


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Rex Baucom said:
Rear drive shaft is a new Adams drive shaft with new u joints. Everything associated with the front drive shaft is def stock and probably original.

I'm going to dive in this weekend and check it out. Good to know about the gear. The jeep drives great, the gear are probably fine and they are broken in very nice.


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Click to expand...

Interesting that it is an Adams. Not bad-mouthing but, others that have mysterious vibration issues are also using Adams.
 
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Rob5589 said:
Interesting that it is an Adams. Not bad-mouthing but, others that have mysterious vibration issues are also using Adams.
Click to expand...

I'm starting to think my choice was not the best. I have both front and rear Adams drive shafts, and I've already had them send me a 2nd front shaft. Brantly was also having issues with his Adams rear shaft and has sent his back to them to check it for balance. I may end up doing the same with my rear, cept I'll take it to a local drive shaft shop. Going to replace my trany mount and rear diff yoke to rule them out first.
 
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Could be purely coincidence, or not. Let's be honest, a drive shaft is a simple component. It shouldn't have to be replaced unless it gets damaged. Shit happens but, sending out bad one's that are replaced almost immediately it poor workmanship.
 
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Rob5589 said:
Could be purely coincidence, or not. Let's be honest, a drive shaft is a simple component. It shouldn't have to be replaced unless it gets damaged. Shit happens but, sending out bad one's that are replaced almost immediately it poor workmanship.
Click to expand...

I hope it's not the rear. I know its spinning faster now but wasn't vibrating before. I will do my part first before I say anything but I won't be happy if it's the rear. That drive shaft is less than 90 days old. I wonder how fast they spin it when it's balanced???


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Rex Baucom said:
I hope it's not the rear. I know its spinning faster now but wasn't vibrating before. I will do my part first before I say anything but I won't be happy if it's the rear. That drive shaft is less than 90 days old. I wonder how fast they spin it when it's balanced???


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Click to expand...

Don't know that answer, but I do know this, I emailed James Adams a few days ago to ask him if they balance their drive shafts with the u-joints installed. He said yes, they do. Just wanted to know to rule out a u-joint issue.
 
IMG_4593.JPG
After spending god only knows how much to fix this problem (my wife will never really know!) I ended up doing a locking hub conversion on the front axel. Vibration and harmonic noise 100% gone.
 
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I pulled the front drive shaft and that pulsating vibration is gone. So something is definitely a foul with front drive shaft. I am about to set up my front adjustable control arms and track bar. I guess I should start with my pinion angle being dead on and see if they are still there. If the vibes are gone then, working on setting caster.

If they are still there. What should I do first before considering a new drive shaft???
Get new U joints?? Have it balanced?? Rebuild???

As for the rear, my pinion angle is dead on 17 degrees. Drives smooth as everything until about 70 mph. I get a vibration sensation. No where near as bad and I can hardly feel anything. Could this be more of a result of worn tires or crappy road conditions??? I only feel it in my seat and it's ever so slight.
I need new tires bad so I feel it's a contributing factor to the ride feel


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I know it's a lot of work, but now that you think you've isolated it to the front drive shaft, just to be sure, remove the rear drive shaft and put the front one back on and go for a 4hi drive. Post your results. I've been where you are at now.
 
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