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Discussion Starter #1
Good day to everyone,

Just finished an SOA conversion on my 95 YJ and having some driveshaft vibration issues. I used the RC perches and installed a tom woods SYE. Unfortunately I did not have the drive shaft when I set my pinion angle and I am pretty sure I set my pinion angle incorrectly and that is causing my vibration. I mainly feel it when I am applying throttle going forward and it settles down at low throttle conditions. Also have no vibrations in reverse.

Using my protractor I currently have 17 or 18 degrees on my drive shaft and 23 or 24 degrees on my pinion.

Basically looking for some confirmation that I need to install a 6 degree wedge to drop my pinion angle down and if 6 degrees will be enough?

Thank you for your time and I appreciate your help.

Shawn
 

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Is your drive shaft balanced? Sometimes if you undo a u joint they are sapost to go back only one way because that's how the shaft was balanced.
 

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When doing a rear cv drive shaft you should be around 1 to 2 degrees of difference between the pinion angle and the driveshaft angle. With the pinion angle being lower. Get an angle finder to find out for sure what the angles are but that would definitely cause vibrations
 

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Discussion Starter #6
Thanks for the reply Dark. I did use an angle finder to get those numbers. I wish I would have waited for the drive shaft to come in before welding up the rear perches. Could have saved myself the headache. Oh well...something to consider when I pick up an 8.8

Do you think 6 degrees will be enough or should I try to get my hands on a 7 degree?
 

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No, 3 to 4° only, you have to think when you shim the pinion back down it will change the drive shaft angle too
 

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Discussion Starter #8
Thanks a bunch. I didn't even think about the DS angle changing as I brought the pinion angle down. I was trying to wrap my head around the theory so I picked up a pen and used my finger to simulate what would happen. ******* science.
 

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What springs do you have? Do you have a traction bar? Without a traction bar and stock springs you should have it set about 5-6 degrees below being pointed directly at your TC Yoke. The reason why is when you hit the gas it rotates up about 5-6 degress and points at your TC. If you dont set it low enough it will rotate past the TC and cause a lot of vibration, as well as chew up the joints. If you have a traction bar you should still be 2-3 degrees below pointing directly at the TC since it will still rise a bit when you step on the gas. Both of those measurement are with stock springs. If you have rubicon springs or other firmer lift springs and no traction bar I it would still be 2-3 degrees low. I am actually not going to be using a double cardan shaft anymore myself. I killed two of them in a few months from beating on them. I am going with 1350 yokes and a normal strait shaft on reccomendation from IBuildEmBig. Hopefully vibration is minimal. My 8.8 Pinion is 2 Degrees below pointing directly at the TC Yoke so I should be fine. All said and done though, if your shaft is not lined up with the TC yoke when under power you want it low, not high. High kills them faster from what I am told. Your pinion should not rotate past the point where it lines up with the TC yoke no matter what.
 
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