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

bobthetj03

vibrajeep
Supporting Member
Ride of the Month Winner
Feb 3, 2017
9,160
NorCal
I've been bouncing around questions about my vibration issues in other jeeper's vibration threads, so I figured I better just start my own thread on the matter.

As the title states, I had my axles re-geared from 3.73 to 4.56. Immediately after re-gear I developed a vibration above 50 mph. It feels like a drive line vibration in my mind. Faster I go the worse the vibe gets. Before the re-gear the jeep drove smooth as glass to 75 mph.

Let's hear your thoughts....
 

Chris

Administrator
Staff Member
Sep 28, 2015
38,757
Salem, Oregon
The very first thing I am going to suggest is having a good and reputable shop check the wheels / tires to make sure they are balanced. This often times ends up being the case.

Sure, it's awfully coincidental that it happened right after the re-gear, but sometimes coincidences happen.
 
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lovemachine

TJ Enthusiast
Supporting Member
Feb 13, 2017
985
Indiana
I regeared from 3.73 to 5.13. I had no vibrations whatsoever before hand.

After I regeared, I had vibrations. I removed the front driveshaft, no vibrations. Assuming it was the u-joints, I replaced them. Installed the driveshaft, vibrations.

I took the shaft to a driveshaft shop, and it turns out it was bent. Never had any problems with it before, but because it was spinning faster, it appeared.

Had a new driveshaft made, and all the vibrations are gone.
 
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bobthetj03

bobthetj03

vibrajeep
Supporting Member
Ride of the Month Winner
Feb 3, 2017
9,160
NorCal
The very first thing I am going to suggest is having a good and reputable shop check the wheels / tires to make sure they are balanced. This often times ends up being the case.

Sure, it's awfully coincidental that it happened right after the re-gear, but sometimes coincidences happen.
Stranger things have happened I suppose. To add information, I remove the front drive line, the vibes go away.

I regeared from 3.73 to 5.13. I had no vibrations whatsoever before hand.

After I regeared, I had vibrations. I removed the front driveshaft, no vibrations. Assuming it was the u-joints, I replaced them. Installed the driveshaft, vibrations.

I took the shaft to a driveshaft shop, and it turns out it was bent. Never had any problems with it before, but because it was spinning faster, it appeared.

Had a new driveshaft made, and all the vibrations are gone.
I discovered similar. Started by removing the front drive line and vibes would be gone. Purchased a new Adams drive shaft, installed it, and vibes came back, so I called James Adams. He sent me a second new drive shaft, installed it, and vibes still there.

So, I figured something must be wrong with the front re-gear. Maybe the setup was off, so I took the jeep to a local offroad shop and had them check out the front diff. Everything checked out good.
 

Rob5589

Certified video trained differential rebuilder
Supporting Member
Aug 29, 2016
6,368
W Sacramento, Kalifornia
The ring and pinion set up isn't going to cause vibrations, especially in the frt while in 2wd. The front diff is simply "coasting." By lowering the gear ratio you have increased RPM's which are now exposing something that isn't in balance. If the frt drive line being pulled gets rid of the vibration, that is where you should focus your attention. Maybe something in the frt output shaft in the T/C?
 
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bobthetj03

bobthetj03

vibrajeep
Supporting Member
Ride of the Month Winner
Feb 3, 2017
9,160
NorCal
The ring and pinion set up isn't going to cause vibrations, especially in the frt while in 2wd. The front diff is simply "coasting." By lowering the gear ratio you have increased RPM's which are now exposing something that isn't in balance. If the frt drive line being pulled gets rid of the vibration, that is where you should focus your attention. Maybe something in the frt output shaft in the T/C?
That's where I'm heading next. I ordered a new input yoke, and will be doing a SYE soon. New chain, new bearings, etc. It's just strange how these vibes came about with just the gear change and nothing else was altered.
 

Brantley

TJ Enthusiast
Well, since it goes away with the front driveshaft removed, it's gotta be something either in the front transfer case shaft, front driveshaft, or diff.

If I remember right, the front TJ D30 has a crush sleeve in it. My gear guy told me (this is what he told me, none of it is my own thinking) that if the crush sleeve is tightened too much from where it should be, then vibrations can develop from slop in the front diff. Do you have any rotational slop in the yoke if you remove the driveshaft from it and then it back and forth by hand? Some slop might be normal but excessive is not.

I had a dumbass shop changed my D35 yoke and they overcrushed the sleeve, based on the diagnosis from my gear guy based on the amount of rotational slop he watched from my video I recorded for him. Got vibrations as a result. I can't even get it warrantied because it's near my parents house and I live an hour and a half away. I suppose it will be remedied when I finally regear again.
 
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Rob5589

Certified video trained differential rebuilder
Supporting Member
Aug 29, 2016
6,368
W Sacramento, Kalifornia
A crush sleeve is to set pinion bearing pre-load. A D30 uses shims to set pre-load. If it is over tightened the pinion bearings can be destroyed. If they burn up, they can get loose, it is something you could feel by turning the yoke and feeling for roughness, looseness, etc. If the pinion became real loose it would likely trash the seal causing a leak. It would take an experienced hand to determine if there is any damage.
 

Brantley

TJ Enthusiast
I'm no differential expert, I just know that I now have vibes after my yoke install and I'm pretty darned sure my driveshaft is balanced perfectly along with my perfect pinion angle. Figured I'd throw in my experience with mine now vibrating from what seems to be the crush sleeve as the only cause that makes sense. I will state, no seals have leaked yet. I'm not sure what's up with mine but hopefully he gets his figured out.
 

Rob5589

Certified video trained differential rebuilder
Supporting Member
Aug 29, 2016
6,368
W Sacramento, Kalifornia
Well, since it goes away with the front driveshaft removed, it's gotta be something either in the front transfer case shaft, front driveshaft, or diff.

If I remember right, the front TJ D30 has a crush sleeve in it. My gear guy told me (this is what he told me, none of it is my own thinking) that if the crush sleeve is tightened too much from where it should be, then vibrations can develop from slop in the front diff. Do you have any rotational slop in the yoke if you remove the driveshaft from it and then it back and forth by hand? Some slop might be normal but excessive is not.

I had a dumbass shop changed my D35 yoke and they overcrushed the sleeve, based on the diagnosis from my gear guy based on the amount of rotational slop he watched from my video I recorded for him. Got vibrations as a result. I can't even get it warrantied because it's near my parents house and I live an hour and a half away. I suppose it will be remedied when I finally regear again.
There is going to be "slop" as you call it in all diffs. Remember, the backlash is .008-.012 for most diffs, so that is a minute amount that you may or may not be able to feel. But, you will have "slop" between the carrier and spider gears and spider gears to axles. This can feel excessive when in actuality it is not. Detroit lockers have what some think is excessive "slop" when in reality, it is perfectly normal. In an open differential, rotating the yoke an inch or so is likely normal.
 
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Rob5589

Certified video trained differential rebuilder
Supporting Member
Aug 29, 2016
6,368
W Sacramento, Kalifornia
I'm no differential expert, I just know that I now have vibes after my yoke install and I'm pretty darned sure my driveshaft is balanced perfectly along with my perfect pinion angle. Figured I'd throw in my experience with mine now vibrating from what seems to be the crush sleeve as the only cause that makes sense. I will state, no seals have leaked yet. I'm not sure what's up with mine but hopefully he gets his figured out.
In order for you to get vibs from a simple yoke change, the yoke would likely be loose. If they over loaded the pinion bearing and they took a sh&t, then it can become loose and cause vibrations. On occasion, simply clocking the drive line 180 degrees from its original position can induce vibration. A crush sleeve is sandwiched between the front and rear pinion bearings. It is simply a metal sleeve that is dimpled/relieved to allow it to be "crushed" ie, shortened, to obtain the proper bearing pre load.
 

Brantley

TJ Enthusiast
In order for you to get vibs from a simple yoke change, the yoke would likely be loose. If they over loaded the pinion bearing and they took a sh&t, then it can become loose and cause vibrations. On occasion, simply clocking the drive line 180 degrees from its original position can induce vibration. A crush sleeve is sandwiched between the front and rear pinion bearings. It is simply a metal sleeve that is dimpled/relieved to allow it to be "crushed" ie, shortened, to obtain the proper bearing pre load.
Tried that...I actually have two driveshafts and they both vibrate every which way I install them. I've tried all 4 possible positions for each shaft, vibes on all of them.

Not the end of the world, I'll figure it out at some point. I'm hopeful that it's in my diff simply because it'll be eliminated when I get my Super 35 installed if so. If that doesn't fix it, I'll look into transfer case shafts and both of my driveshafts possibly being out of balance...

Not trying to steal Bob's thread here though so I'll probably stop talking about my problems.
 
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bobthetj03

bobthetj03

vibrajeep
Supporting Member
Ride of the Month Winner
Feb 3, 2017
9,160
NorCal
My front D30 takes a crush sleeve. I had another shop inspect the front diff. They double checked pinion pre load, back lash, and gear tooth pattern. They told me everything was within spec. I have very little rotational play on the front yoke when the drive shaft is removed, and absolutely zero back and forth/up/down play in the yoke. I feel pretty confident that the front diff and the front drive line are not the problem. So, that leaves from the TC front yoke and back. I've double checked the torque on the TC input yoke, and it is tight. There also is no vertical/horizontal play or in/out play in the yoke. I have MC control arms up front. The lowers are new, and the uppers are 2 years old. Pinion angle is in a good place( I verified this with a question to @mrblaine.)

What are your thoughts of the axle side control arm bushings being worn out to the point that they may amplify vibes that can be felt after reaching a certain speed? My axle side bushings are the original Clevite bushings with 150K miles on them.

Also, what are your thoughts about the possibility that my rear drive line is amplifying vibes only when the front drive line is installed, kind of like the front drive shaft is acting like a tuning fork or something creating the speed related vibes? Just thinking outside of the box a little. I've been dealing with this for almost a year now. The new gears have over 8k miles on them, and not being able to drive the jeep above 60 mph is getting old.

FYI, I removed the rear drive shaft and replaced the ujoints. I did notice a little bit of rotational play in the slip yoke on the TC rear output. I have MC double adjustable rear upper arms that are new, and Currie lower rears which are 5 years old. The JJ's look good. I have adjusted the rear pinion angle to be parallel with the TC rear yoke angle per a 2 ujoint drive shaft config.
 

Rob5589

Certified video trained differential rebuilder
Supporting Member
Aug 29, 2016
6,368
W Sacramento, Kalifornia
Ok, so here is a totally off the wall thought: Could placing the Jeep on a lift, bringing all four wheels off the ground and hanging in the air for a while, somehow throw off driveline angles? My thinking, and am probably way off, if anything was even slightly loose or out of spec, when putting it back on the ground things settled differently? You can call me a dumbass, I won't be offended :D
 
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bobthetj03

bobthetj03

vibrajeep
Supporting Member
Ride of the Month Winner
Feb 3, 2017
9,160
NorCal
Ok, so here is a totally off the wall thought: Could placing the Jeep on a lift, bringing all four wheels off the ground and hanging in the air for a while, somehow throw off driveline angles? My thinking, and am probably way off, if anything was even slightly loose or out of spec, when putting it back on the ground things settled differently? You can call me a dumbass, I won't be offended :D
No such thing as a dumb question here. I've literally had the jeep on and off the lift 100 times and I don't think it would effect the bushings or ujoints in a bad way. The axles will only drop as far as the shocks will let them. Nothing binds when the jeep is on the lift.
 

jeepndogs

TJ Enthusiast
Mar 5, 2017
616
Crete, IL, United States
No such thing as a dumb question here. I've literally had the jeep on and off the lift 100 times and I don't think it would effect the bushings or ujoints in a bad way. The axles will only drop as far as the shocks will let them. Nothing binds when the jeep is on the lift.

Since you and I are having very similar issues I will give you an update on what I did today. I replaced the front TC output shaft yoke and it made a slight improvement. I swapped out my MT Deggan 88's Mud terrain with a friends pretty well worn BFG all terrains and there was also a noticeable improvement. I am starting to think that this is possibly a combination of several small vibrations that all add up.

What angles are you running your front shaft and pinion at? I have about a degree higher on the pinion. I just measured two stock Ljs and they are about 3 degrees high.
 
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mrblaine

TJ Expert
Supporting Member
Nov 20, 2015
5,644
Quail Valley, CA
FYI, I removed the rear drive shaft and replaced the ujoints. I did notice a little bit of rotational play in the slip yoke on the TC rear output. I have MC double adjustable rear upper arms that are new, and Currie lower rears which are 5 years old. The JJ's look good. I have adjusted the rear pinion angle to be parallel with the TC rear yoke angle per a 2 ujoint drive shaft config.
The only angle that matters is the one where it doesn't vibrate. So, I never give anyone an angle or much of anything except to start low in the back and move it up a 1/2 degree at a time until it changes and correlate the change with what you've done and keep messing with it until you get it as good as possible. Also, with problematic rigs, I remove the front shaft so I'm only working with one set of vibes.
 

mrblaine

TJ Expert
Supporting Member
Nov 20, 2015
5,644
Quail Valley, CA
Ok, so here is a totally off the wall thought: Could placing the Jeep on a lift, bringing all four wheels off the ground and hanging in the air for a while, somehow throw off driveline angles? My thinking, and am probably way off, if anything was even slightly loose or out of spec, when putting it back on the ground things settled differently? You can call me a dumbass, I won't be offended :D
Not a dumbass but the forces seen from the hanging axles are far less than what it sees hitting bumps and cornering and or braking and acceleration forces.
 
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bobthetj03

bobthetj03

vibrajeep
Supporting Member
Ride of the Month Winner
Feb 3, 2017
9,160
NorCal
Thanks for your input guys. I have a suspicious feeling my tires are also playing a role. I have a jeep run next weekend, then like Blaine mentioned, I'll pull the front shaft and get the rear as good as I can, then move to the front. I also want to swap tires with a buddy's jeep and see what we net.