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Oscillating Vibration


d.markowski

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Hey all, I have a 2000 TJ Sahara with 35s, 4.88s and eaton e lockers, 4" lift with currie springs, metal cloak trackbars, metal cloakdouble adjustable control arms, and currie correctlink tierods and draglink. Most importantly with a Teracon SYE kit and a Tom Woods double cardan driveshaft. I have the proper geometry for a CV driveshaft (0 angle between driveshaft and rear axle). I've been struggling with an oscillating vibration that just seems consitent with improper driveshaft geometry. It is noticable from 40 mph + for like the last 5 or 6 years now. I've toyed again and again with slight adjustments to the control arms thinking maybe the driftshaft to axle angle was +or- 2-3 degrees off or that there is some slight upward motion of the rear diff when accelerating but nothing seems to work. Was toying with the idea of a dropping the transfer case an inch or two to see if that helps but that seems unnecessary considering my setup should be fine. Anyone have any ideas what could be going on here? I've tried much more too. I've exhausted all my options and spent :(
 

bobthetj03

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Did it start after you re-geared? Have you tried pulling the front drive shaft, then the rear to isolate which one is causing it?
 
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d.markowski

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Did it start after you re-geared? Have you tried pulling the front drive shaft, then the rear to isolate which one is causing it?
It was there well before my regear so we can cross that off the list. I'll pull front driveshaft when I get a chance and try that first. After reading some of the other vibration posts, could be a ujoint in front driveshaft. Didn't think that could be it because they look good but I'll start there. Def not the rear driftshaft ujoints because that shaft was brand new and the problem was still there. Thanks, I'll post an update in next week as Im out of town until Sunday.

Just a quick add to the problem. I orginally noticed this years ago. ~ 4 years when I got rid of the TC drop and installed SYE and TW double cardan driveshaft. I know I changed the geometry of the diff and driveshaft correctly. It's just got in my nerves enough finally to want to solve it before I break something.
 

bobthetj03

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I'm 2 years and counting for mine. Re-gearing initiated mine though. I've isolated mine to the rear ds, so I have little recourse.
 

AndyG

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Most shops start with pulling the front driveshaft when chasing a vibe.

There can be so many things, including harmonics. Be patient and thorough is my best advice, and don't rule out freaky things.
 
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d.markowski

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Most shops start with pulling the front driveshaft when chasing a vibe.

There can be so many things, including harmonics. Be patient and thorough is my best advice, and don't rule out freaky things.
So. I’ve had the new driveshaft balanced twice and they said it was fine. I pulled the front driveshaft and the vibration got better but it’s still there. I have to turn off my music to really notice it. I’m beginning to wonder if I’m just being too picky or if there is actually an issue. Ughhh
 
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d.markowski

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This geometry looks good right?!

image.jpg
 

AndyG

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Well first, if it was balanced twice by the same shop that doesn't tell you anything... The reason I say that is I was dealing with a shop and they weren't doing the work correctly .... the thinking that does things wrong usually can't fix it.

I'm not sure if you ran it with the front only and not the back... But that is a good consideration to do that and put it in four-wheel drive.

Don't rule out things with the wheels and tires... Some guys even go so far to borrow a set.

I've also jacked one up and ran it up to speed and I've been able to figure out an issue.

A very slightly bent axle.

A drive shaft that is slightly bent... This has to be determined with a dial indicator.

There's more to it than one post can cover and we've had threads that ended up looking like Bibles...

The best thing I can tell you is they are not trying to chase down but once you solve them... You will be so glad you spent the time.

@Jerry Bransford says that vibrations don't need to go unchecked because they can lead to other problems..I agree.
 
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AndyG

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To me, just whiskey eyeing it, your pinion looks a couple degrees high.
That's exactly what I was about to post and if anything it should be down just a tad.. to allow for lift under torque load.

If you can't get a good reference from the side put your angle gauge on the back of the differential on the left or right there is a flat spot then you can Anderson track 90° to get your angle it needs to be dead in line with the drive shaft or one to two degrees lower.

Also look and make sure if the shaft is built in phase... It's rare ... but it's possible someone could build one out of phase... We had the best shop in town build one like that for me...I now use a shop out of town.

The fact that you've had it for a long time does it make me think it's the tires and makes me doubtful of the pinion angle a little bit as much as it makes me wonder if you could have a drive shaft that is slightly bent. Keep in mind man this is just a forum even with the best of intentions a lot of times we're just guessing trying to help you.
 
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Vtx531

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Could be dozens of different possibilities. Just go down the list. A dial indicator will be your best friend.

Here are things off the top of my head:

Wheel bearings
Pinion bearings
Carrier bearings
Tcase input or output bearings
Transmission bearings
Tire balance
Tire runout
Wheel runout
Driveshaft (front or rear) runout (including loose splines)
Driveshaft balance
Driveshaft ujoints worn
Driveshaft ujoint runout (clips proper width in thousandths for sidetoside play)
Front axle ujoints (worn or runout)
Engine mounts
Transmission mount
Pinion angles
Control arm bushings
Muffler
Exhaust mounts

Etc etc etc

Sounds like you already ruled out a couple possibilities.

I would recommend NOT focusing repeatedly on issues that have already been checked and ruled out. Check it and move onto another item. No point in getting a driveshaft rebalanced three times!
 
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d.markowski

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Well first, if it was balanced twice by the same shop that doesn't tell you anything... The reason I say that is I was dealing with a shop and they weren't doing the work correctly .... the thinking that does things wrong usually can't fix it.

I'm not sure if you ran it with the front only and not the back... But that is a good consideration to do that and put it in four-wheel drive.

Don't rule out things with the wheels and tires... Some guys even go so far to borrow a set.

I've also jacked one up and ran it up to speed and I've been able to figure out an issue.

A very slightly bent axle.

A drive shaft that is slightly bent... This has to be determined with a dial indicator.

There's more to it than one post can cover and we've had threads that ended up looking like Bibles...

The best thing I can tell you is they are not trying to chase down but once you solve them... You will be so glad you spent the time.

@Jerry Bransford Bransford says that vibrations don't need to go unchecked because they can lead to other problems..I agree.
I’ll try the front driveshaft next and remove rear.
 

JMT

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How does this look?
You might try posting pics again. Not sure what you did, but I'm not seeing the pictures. Do you have an angle finder you can use to measure the angles?
 
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d.markowski

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You might try posting pics again. Not sure what you did, but I'm not seeing the pictures. Do you have an angle finder you can use to measure the angles?

I don’t. Guessing getting it perfectly straight +- a degree is gonna be pretty hard by eyeballin it. What do you suggest? I had a cheap magnetic one and I could never really find a place to measure from that’s perfectly flat...

FD18292B-96D6-40CE-B054-C48EE6A727E3.png
 

JMT

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I don’t. Guessing getting it perfectly straight +- a degree is gonna be pretty hard by eyeballin it. What do you suggest? I had a cheap magnetic one and I could never really find a place to measure from that’s perfectly flat...

View attachment 213023
If you have the cheap magnetic one, level it on the ground with your jeep on level ground. Put it on the driveshaft on the bottom or the top. Write that angle down. On the other side of the diff, toward the back of the jeep, on either side of the cover is a flat section. Put your angle finder on either side of that flat section and write that angle down. They should be the same angle.
 

AndyG

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If you have the cheap magnetic one, level it on the ground with your jeep on level ground. Put it on the driveshaft on the bottom or the top. Write that angle down. On the other side of the diff, toward the back of the jeep, on either side of the cover is a flat section. Put your angle finder on either side of that flat section and write that angle down. They should be the same angle.
Adding to this...and correct me @JMT if I'm wrong, that appears to be a Dana 44, and the 2nd horizontal rib on the housing may line up with the pinion...if so...it's pretty high. Maybe more than you think. A jar of water and a marker can tell you alot if you can't get a gauge.

Here's what you need to do. It's Christmas Eve ...walk in the house, tell them Santa ain't coming til his sleigh doesn't have vibes, and get everybody out in the garage to help, Let us know how that works.

Also, and this is really important, it's a good time to tell the kids and grandkids the truth about Santa Claus....he was shot down in a helicopter over the Soviet Union.
 
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