drivetrain vibration after lift?

Hey All,
I just finished a 2.5" lift on my 74 cj5... I now have a vibration in the drivetrain when in the 40 to 50 mph range....wondered if anyone has an illistration on how to measure the pinion angle from the transfer case to the dana 44 rear ? I borrowed a magnetic protractor just dont understand how to use it?

 

here's some read, hope it can help

http://www.4xshaft.com/

 

First step is to check the condition of the u-joints. You should be ok with 2.5" lift, I would think. But the increased angle could exacerbate a worn joint.

You want this article to start.

http://www.4xshaft.com/driveline101.asp

There's not much to the protractor. You put it on the driveshaft or one of the pinion yokes to measure the angle. Once you have the angles, look at the illustrations in the linked article for insight. You want the axis of the pinion and the transfer case to be parallel. Once they are parallel, the angle of both u-joints will be the same. Then, you can assess whether the u-joint angle is too much or ok.

 

so after my lift... on level ground my transfer case is 0 degrees on the protractor and my dana 44 rear is 16 degrees, both measured on the flat side of the pinion yoke... now my rough country lift kit came with 2 degree shims on the rear springs and the instruction say to have the fat part of the shims facing to the inside of the jeep. that points the axle yoke upward, giving me the 16 degrees...I think this might be wrong? anyway I will read the article and see whats what. keep you posted.

 

My 2.5" kit came with 2deg shims as well. At first I installed them and resulted in a vibration like you describe. I removed them, and now no vibration. Therefore, I discarded the shims. My lift is a 4wd Hardware branded lift. I have new driveshafts with new universals, so I was confident I didn't have a bad joint.

 

I put a 2.5" springs on my 74 CJ5. Have the Jeep T-18 4 speed. I had a slight noise at higher speeds when I would just remove my foot from the gas pedal. The noise was only present when the drive drain was in a neutral state. As soon as the drive train was under load the noise would go away. During this time frame, I was running 30.5 tires. A few months ago I picked up some 33 BFG Mud tires. Now the noise is completely gone. Seems the larger tire helped with the angle of the drive line and no more noise when drive train is in a neutral state.

 

Just changing tire size will NOT change the u-joint angle. Better look closer. The symptoms you described are classic of u-joint angle vibrations. Get an angle finder and check them. If they are off they can cause bearing damage in the transfer case output, transmission, and rear differential. Not to mention the u-joints.


Sent from my iPhone

 

Just an update...I removed my leaf springs and reversed them so now the axle shims are fat side towards the outside of the vehicle. This is opposite what the instructions said to do in my rough country 2.5" lift kit. So now my rear axle horizontal axis is with in 1 or 2 degrees of my transfer cases horizontal axis. So were all good there.
Now the driveshaft angle seems to be a little two steep, The rear pinion yoke and drive shaft are actually making light contact with each other at the twelve o-clock position. This weekend I am going to try and lower my transfer case to see if that will help make the angle less sharp? Does that seem logical?

 

Sounds like by putting the fat portion of the springs facing aft would throw the pinion down increasing your angle. I believe the goal is to reduce that angle between the rear diff and the transfer case by bringing the pinion yoke up so that it faces the output on the transfer case.

 

It seems odd your transfer case is at 0 degrees at the yoke.

I suggest pulling the shaft and holding the angle gauge against the flat part of the transfer case yoke (where the u-bolts go) and seeing how many degrees tilted from 90 you are and do the same on the yoke on the diff. Then put the shaft back on and measure the angle of the shaft itself as installed.

Post those three numbers w/ photos of the angle gauge in each of those three positions to remove any change of ambiguity from which way you have the angle gauge oriented and we should be able to tell you where you need to go w/out a bunch of trial and error.

 

This is were I would start. If you didn't lower the transfer case output after 2.5" of lift you are likely to get some vibration.

 

So I removed my rear leaf springs for a third time, removed the shims as oleblue suggested....and finally my jeep is driving with no drive line vibration. Thanks all for your input.

 

The goal is having the same angles on both T-case and rear end (within 3 degrees max). Making them parallel. The only time you raise & "point" the rear yoke at the T-case output yoke is when you are running a CV joint at the T-case.

 

If you did not have a CV joint and the diff yoke was inline with the out put of the TC why would that be bad? It seems to me the TC yoke would still have the same angle either way and the diff would have very little, reducing wear. If one thought of it in the reverse it could be said that to great of angle on the "U" joints causes more friction and therefore early failure. Educate me
THX
Dave