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Forum Home > Modifications > Drive line vibration question.

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Member
Posts: 194

I have a Super Lift 4” short arm lift on my TJ and I am running 33x12.50x15s.

The Lower links front and rear are “fixed” as in no flex in the link or adjustment.

The Upper links are stock stamped steel.

Problem: Drive line vibration

Easy solution: replace rear driveshaft with a Tom Woods CV type shaft.

Issues:

Per Tom Wood’s Inc. the pinion must point at the Transfer case for the CV shaft to work properly.

My Pinion is pointed down. My Transfer case has been lowered and the output is pointed down at the diff . This is most likely the reason for the vibration as the angles are different on each end.

I have “to my knowledge” no way to adjust the pinion angle Due to the “Fixed” Control Links.

If I can adjust the angle without replacing the links let me know how to do that.

What is my best option to correct the vibration?

1. Do I replace the upper Stock links with adjustable links front and rear?

2. Do I replace the Lower links front and rear with adjustable links and keep the factory steel uppers?

3. Do I replace them all with adjustable links upper and lower, front and rear?

Are there any issues I am not considering in this solution?

More flex in my system would be nice as well.

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August 6, 2012 at 4:47 PM Flag Quote & Reply

Flexer
Member
Posts: 265

There are a few main causes for drive line vibes.

1- Steep drive line angles due to a lift (many lift kits compensate with a t-case drop)

2- UJoints going bad

3- improperly balanced drive shaft

4- Something horribly wrong in the diff (unlikely but possible)

I would be surprised if you are having front end drive line vibes... test it by pulling the front driveshaft and driving around...then replacing it and pulling the rear driveshaft and driving around (4 wheel high..lol).

MOST LIKELY it's just the rear.  The main front end problem is death-wobble... and that's a whole different discussion.

Inspect the ujoints when you have the drive shafts out.  if it's just u-joint then it might be a simple fix.  ... ( unless your name is Doug then it's an all day affair to repair one UJoint in the front Axle... not because it was Doug...Doug seemed quite nice!  ...but because the "new to Doug"' Jeep had a little rust...  )

Assuming it's just the rear...and you have to do something bigger...

A slip yoke eliminator kit (SYE) is commonly used to replace the output shaft of the transfer case (which has the slip yoke) with a fixed output shaft and then put a CV drive shaft in which has slip splines in the drive shaft (I'm assuming you're getting the drive shaft from Woods... does he sell SYE kits too?)  I've performed this a couple of times.  It's not trivial but you don't have to have a full machine shop to do it.

(aside: If you do that it's also useful to put in a 4:1 kit at the same time... )

Yes, the proper way to set up a cv drive shaft is to point the punkin' at the output yoke of the SYE kit installed transfer case.  That can be done a few different ways:

1- Shorter lowers (I think this is most common but I haven't faced it in a TJ)

2- Longer uppers

3- both

4- Grind off and re-weld all the bracketry (unlikely...waaaaaayyyy too much work)

Here was my thought:  If you adjust the uppers then you might hit the gas tank....so go with adjustable lower links and adjust them.

Ok, my thoughts are done.

 

 

 

--

'94 Jeep YJ 4.0L, 35" BFGs, Atlas 2 tcase, D44 front, 14b rear, detroit front, ARB rear, 4.56 gears, Warn winch, Onboard air, some rock rash. 

WrenchingSeasonBlog

August 6, 2012 at 7:55 PM Flag Quote & Reply

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Posts: 194

Thanks for the info. I guess I should have included the fact that it is a Rubicon. so I have the fixed yoke and the 4to1 stock. I will remove both shafts one at a time and see what I get. It feels like it is only in the rear but that will let me know for sure. I guess the pinion angle adjustment will be based on $$$$$. I will shoot for upper and lower just for the extra flex. I will keep an eye on the tank as well when I do it. (Yes I plan to get the Tom Woods Rubicon CV shaft as he is a sponsor of "Rock the Ozarks" and that will provide me with a spare stock shaft just in case)

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August 6, 2012 at 10:56 PM Flag Quote & Reply

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