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Weird vibration at cruising speeds

Justin Homan

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Hi guys, on my most recent trip to the Sierra's my jeep developed an odd vibration once its up to speed, the weird part is that it doesn't happen if im accelerating or decelerating it only happens when i try to keep the same speed. i had my tires balanced today and its still happening i also checked the u joints and none need replacing. It feels very much drive-line related but im not sure what it would be. Anybody have the same issue? Any Ideas?
 

AndyG

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Well , anything moving is a suspect . First thing Is pull the front shaft , if it goes away , work in that direction.
 

AndyG

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Thanks, ill give that a try tomorrow!
It’s what experienced shops do first . It’s a starting point .

it’s good it’s not on accel/ decel......I’d check my transfer case mounts , skid plate tightness, lube u joints and feel for excessive heat , gear oil , and use my nose .

lifting the rear and getting it up to speed can help, just be cautious .

if the u joints have any age , it’s hard for me to trust them.

if you can soak them individually, one at a time , in spray lube and it stops briefly ...you may have a dry one heating up.

Keep us posted..,when you learn, we all learn.
 
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Justin Homan

Justin Homan

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Brentwood California
It’s what experienced shops do first . It’s a starting point .

it’s good it’s not on accel/ decel......I’d check my transfer case mounts , skid plate tightness, lube u joints and feel for excessive heat , gear oil , and use my nose .

lifting the rear and getting it up to speed can help, just be cautious .

if the u joints have any age , it’s hard for me to trust them.

if you can soak them individually, one at a time , in spray lube and it stops briefly ...you may have a dry one heating up.

Keep us posted..,when you learn, we all learn.
Sweet! Ill keep yall up to date with what I find.
 
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Justin Homan

Justin Homan

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Joined
Oct 31, 2019
Messages
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Location
Brentwood California
It’s what experienced shops do first . It’s a starting point .

it’s good it’s not on accel/ decel......I’d check my transfer case mounts , skid plate tightness, lube u joints and feel for excessive heat , gear oil , and use my nose .

lifting the rear and getting it up to speed can help, just be cautious .

if the u joints have any age , it’s hard for me to trust them.

if you can soak them individually, one at a time , in spray lube and it stops briefly ...you may have a dry one heating up.

Keep us posted..,when you learn, we all learn.
Today i got the front driveshaft off and the vibration is still there, when i get a chance im gonna go through and grease the rear u joints and if that doesnt fix it i will remove the rear driveshaft and inspect the insides of the u joints
 

AndyG

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Today i got the front driveshaft off and the vibration is still there, when i get a chance im gonna go through and grease the rear u joints and if that doesnt fix it i will remove the rear driveshaft and inspect the insides of the u joints
Remember, you can pull the rear , slap it in 4wd , and drive with the front only as well.
 
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Justin Homan

Justin Homan

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Remember, you can pull the rear , slap it in 4wd , and drive with the front only as well.
I can but with my spartan locker up front its impossible to turn, i should have time to play with it more this afternoon so ill let yall know what i find.
 
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Chris

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Sounds like tire vibrations to me.

Just because you had them recently balanced doesn't mean anything unfortunately. Often times it can take 2-3 attempts to get them perfect, especially if the person / shop doing it doesn't have much experience with larger 4x4 tires.
 
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acct21

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close to Austin, Texas -- but not too close!
Had the same issue crop up a few weeks back -- my vibration was only under acceleration above 50mph -- but otherwise 1) it was new, and 2) it was clearly a problem.

I "checked my u-joints" by rocking/twisting/shaking the bejeezus out of the rear driveshaft. No movement or play whatsoever. Started the process of pulling the rear driveshaft to test if it was front or back (started with the back because it felt like it was coming from the back), and as soon as I pulled my first yoke retaining strap, the entire driveshaft was loose at the pinion yoke. Completely disintegrated one of the bearing caps on a 1330 u-joint at the pinion. All the needles were gone, and the cap was starting to fracture.

There is probably a very simple geometry/physics equation that explains it, but essentially you can have a fried u-joint, and no real way of identifying it until you pull the driveshaft.
 
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Justin Homan

Justin Homan

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Sounds like tire vibrations to me.

Just because you had them recently balanced doesn't mean anything unfortunately. Often times it can take 2-3 attempts to get them perfect, especially if the person / shop doing it doesn't have much experience with larger 4x4 tires.
Ive had tire vibrations before and they happened even if i was accelerating, this only happens when staying at the same speed or decelerating slightly.
 
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Justin Homan

Justin Homan

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Had the same issue crop up a few weeks back -- my vibration was only under acceleration above 50mph -- but otherwise 1) it was new, and 2) it was clearly a problem.

I "checked my u-joints" by rocking/twisting/shaking the bejeezus out of the rear driveshaft. No movement or play whatsoever. Started the process of pulling the rear driveshaft to test if it was front or back (started with the back because it felt like it was coming from the back), and as soon as I pulled my first yoke retaining strap, the entire driveshaft was loose at the pinion yoke. Completely disintegrated one of the bearing caps on a 1330 u-joint at the pinion. All the needles were gone, and the cap was starting to fracture.

There is probably a very simple geometry/physics equation that explains it, but essentially you can have a fried u-joint, and no real way of identifying it until you pull the driveshaft.
Im going to pull the rear driveline after work today, hoping its a u-joint as thatll be the easiest fix for me.
 
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Justin Homan

Justin Homan

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Quick update, tore apart my rear driveshaft and all the u joints are good and have no play. I did notice my Atlas output yolk had a solid 1/4 turn of play so i called Advanced Adapters technical support and they think my yolk nut isnt torqued properly. Ill remove the shaft again tomorrow and re-torque it to 150ft-lbs.
 
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Justin Homan

Justin Homan

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So I torqued the transfer case down and the high speed vibration seems too be gone but it now vibrates between about 25 and 40mph which i thought might be driveline angle. long story short re-adjusted that and nothing changed.
 

AndyG

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Got it fixed! Ended up being a loose pinion nut and the axle side u joint whose cap wasnt seated all the way/
Good deal it doesn't take much to shake a TJ around.

Really when you compare them to what we are all driving most of the time which is either a front-wheel drive or rear wheel drive vehicle there is a lot more going on.
 
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Justin Homan

Justin Homan

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Brentwood California
Good deal it doesn't take much to shake a TJ around.

Really when you compare them to collect you are all driving most of the time which is either a front-wheel drive or rear wheel drive vehicle there is a lot more going on.
Definitely, was a good learning experiece though, now i got a better idea how to chase the vibes. Thanks for your help!
 
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