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Old 04-08-2013, 05:31 PM   #1
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Need help with Vibration not DW

Just finished up my registration, so new to the forum here fellas.
Got a small problem that's kinda got me baffled.

2000 TJ with a 4" suspension lift, 2" body lift. Dunlop Radial AT LT305/70R17 tires all around.

Here's the problem. At any speed I get vibration, it gets worse the faster the Jeep goes, but not terrible. When I mash in the clutch the vibration goes away. When I put Jeep in 4WD the vibration goes away at all speeds.

Any ideas? gotta be somewhere in the drive train, but where?

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Old 04-08-2013, 05:35 PM   #2
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Vibration up through the seat of your pants? If so, that vibration sounds like it is probably caused by the 4" suspension lift which is definitely curable.

Did it just start or did it start right after the 4" suspension lift was installed? Which do you have, a t-case drop or a SYE kit and CV driveshaft? If you have a t-case drop, how much of a drop is there? Is there a motor-mount lift installed?

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Old 04-08-2013, 06:36 PM   #3
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Vibration through seat of pants sure. but really noticeable through steering wheel.

Bought Jeep 2 years ago, already lifted. Took off the ridiculous 44x14.5 mudders and it got better. Changed out all u-joints and it got better. replaced track bars, control arm and bushings, tie rod ends and pitman arm with new alignment and got better.

I am sure it has a t-case drop but don't know how much. Should I measure frame to skid plate?

Motor mounts appear stock and the rear driveshaft looks like SYE, it has a rubber boot and 2 u-joints. Is that right?

After all the work I just have this small vibration that drives me nuts and it isn't there in 4 wheel hi. Talked to the guy at the local 4x4 shop, he says it is the pressure plate in the clutch. If that is it I would think it would vibrate any time the clutch wasn't mashed in.

You think it is the driveshaft?
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Old 04-08-2013, 07:01 PM   #4
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How many u-joints total does the driveshaft have, three with two u-joints at the t-case end plus one at the end? Or two u-joints total, one at each end?

By itself, just a normal t-case drop is not enough to cure the vibrations caused by a suspension lift as tall as your 4" suspension lift is.
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Old 04-08-2013, 07:18 PM   #5
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Jerry appreciate your time brother. The driveshaft has two u-joints, one at each end.
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Old 04-08-2013, 07:36 PM   #6
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Ok based on two u-joints total in your rear driveshaft, you do not have a SYE kit, you're still using the OE factory driveshaft since it has a total of two u-joints.

At 4" of suspension lift height, that much height steepens the rear driveshaft so much that it puts those two u-joints at such steep angles that it will make them vibrate. The only way to eliminate the vibes are by reducing their angles. That is done with either with a SYE kit and aftermarket CV driveshaft which has three u-joints, or with an excessively steep transfer case drop which will probably have to be 2", 1" of drop just isn't enough. Or installing a set of 1" taller motor mount lifts... which may not be enough either.

The best way to get rid of the vibrations is by installing a SYE kit which replaces the OE t-case output shaft. That allows a slightly longer aftermarket driveshaft to be installed which is less affected by suspension lift height. But by itself, just a SYE kit is not enough to get rid of the vibes. The other part of the fix that works in conjunction with the SYE kit is a CV (constant velocity) driveshaft which is also known as a double-cardin driveshaft.

A CV driveshaft gets rid of vibrations by eliminating excessively steep u-joint angles. It does that via adding a u-joint to give a total of three u-joints. The rear-most u-joint of a CV driveshaft will have no angle at all on it. The rear axle's pinion shaft with a CV driveshaft will be at the same angle as the driveshaft... so that rear-most u-joint really isn't doing much. What makes a CV driveshaft work is its front two u-joints divide the remaining angle between each other which gives each half as much angle to contend with... which means the angle each has to work with isn't enough to worry about... which eliminates the drivetrain (driveshaft) vibrations.

So the BEST fix is a SYE kit and CV driveshaft. Save up for those two parts, they are the only good fix.

The other TEMPORARY fix is either more t-case drop with longer spacers between the frame and t-case skidplate, and/or installing a 1" motor mount lift. Either of those will decrease your presently excessive rear driveshaft u-joint angles, hopefully enough as a band-aid fix to get rid of the vibes.

It really sounds like the previous owner kludged things together.

The below two illustrations will show the differences between the OE driveshaft & an aftermarket CV driveshaft combined with the SYE kit. The SYE kit by the way replaces the output shaft with a shorter version so a longer aftermarket CV driveshaft can be installed.
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Old 04-09-2013, 12:35 AM   #7
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Whats the angle degree that's acceptable? 8? 16?
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Old 04-09-2013, 05:36 AM   #8
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Give me 10 minutes. I am going to get some photos and will upload. I have a similar thing just at about 100km/hr or about 60 miles/hour (for the americans)

And if you don't mind can you have a look at it Jerry and tell me if i've got the same problem.....I have a strong feeling I do. (I have only had the Jeep about a month and have only taken it that speed a handful of times) I don't do a massive amount of kms
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Old 04-09-2013, 05:51 AM   #9
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Any help is appreciated
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Old 04-09-2013, 05:52 AM   #10
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And those leaks you see are getting fixed tomorrow. Dropping it at the shop at 8.....so they are being taken care of
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Old 04-09-2013, 07:38 AM   #11
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Thanks Jer.
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Old 04-09-2013, 09:15 AM   #12
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OK. So I understand why this would give me vibration. Last question. Why does vibration go away in 4 wheel high or when clutch mashed in?
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Old 04-09-2013, 09:21 AM   #13
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Originally Posted by Rob and TJ View Post
Whats the angle degree that's acceptable? 8? 16?
There is no particular angle that is acceptable/correct for all Jeeps. The angle changes by the suspension lift height & driveshaft length. The acceptable angle is one that matches the requirements of the type of driveshaft used.

OE driveshaft: the rear pinion angle must be the same as the t-case output shaft's angle.... they must be parallel to each other.

CV driveshaft: the rear pinion angle must be the same as the driveshaft angle.

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Originally Posted by jimmy_buckle View Post
Any help is appreciated
It's hard to tell for sure but your rear pinion angle looks good from the photos.
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Old 04-09-2013, 10:30 AM   #14
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OK. So I understand why this would give me vibration. Last question. Why does vibration go away in 4 wheel high or when clutch mashed in?
I would think your u joints are going. When you drop the clutch, your disconecting pressure from turning the shafts. Put pressure on the u joints and she shakes again... Block your tires, put it in N without running. This free's up the shafts to spin by hand. Get under there and spin/rock your drive shafts back and forth. If you feel little bumping, find the loose one. Should be solid without ANY play in 'em.

when you feel the play in a bad u joint, you'll never forget what to look for.
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Old 04-10-2013, 03:18 PM   #15
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Hi There!
I'm new to the forum... but I'm experiencing the same thing a vibration that comes from the seat. I have a 2008 4DR Sahara Wrangler with 4" Teraflex suspension lift kit, 35" Nitto Grapplers, Fox shocks and stabilizer. Have not done any mod's to the driveline or u-joints.... as of yet.

The vibration started the day the lift was installed. It only happens when your going from a stop to acceleration no faster then 5 - 10 mph. If you accelerate or brake the vibration smooths out completely. I completely expected some vibration with the changes, however this vibration is definitely NOT coming from the tires, alignment, or suspension... LOL!

Does anyone have input, I would really appreciate it?
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Old 04-10-2013, 03:48 PM   #16
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4" of suspension lift with no additional drivetrain modifications is enough to cause vibrations in any short wheelbase Wrangler. The problem is your rear driveshaft angle is now so steep from that suspension lift that the rear driveshaft's u-joints are vibrating from excessive angles. The recommended cure is to install a SYE (slip yoke eliminator) kit into your transfer case & replace your rear driveshaft with a longer CV (constant velocity) driveshaft.

Such vibes are not something that can be just lived with as they will eventually start damaging things like u-joints, seals, or bearings.

For the time being you can at least reduce them somewhat by installing an inexpensive transfer case drop kit that lowers the transfer case skidplate an inch. That will help to slightly decrease (but not eliminate) those excessive u-joint angles.

And a big welcome to WF!
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Old 07-06-2013, 01:54 AM   #17
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Jerry,

While I had my trans out to fix the rear main seal and install clutch I installed a SYE in my transfer case to eliminate the vibrations from the 4" lift that was installed by the previous owner. I noticed the spacers on the skid plate for the transfer drop. Should I put these back on or take them off with my SYE and CV driveshaft?
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Old 07-06-2013, 06:26 AM   #18
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Jerry,

While I had my trans out to fix the rear main seal and install clutch I installed a SYE in my transfer case to eliminate the vibrations from the 4" lift that was installed by the previous owner. I noticed the spacers on the skid plate for the transfer drop. Should I put these back on or take them off with my SYE and CV driveshaft?
With the SYE and new DS you don't need the TC drop which is one benefit of the SYE.
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Old 07-06-2013, 10:36 PM   #19
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Originally Posted by MosesTJ View Post

With the SYE and new DS you don't need the TC drop which is one benefit of the SYE.
Thanks... It drives great now!

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