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I installed a SYE and CV with adjustable uppers. The axle is centered under the Jeep and the pinion angle is close to zero, but after looking at it I have a feeling that I might have put the pinion angle just a little too steep. I have slight vibes at 55mph and the faster I go the worse they get. Do vibrations like this come from an incorrect set pinion angle, or would it be something else?

2.5L TJ, 3" lift, D35, AA SYE, Spicer CV

I will try to get pictures tomorrow.

Rear pinion angle should be 1 to 2 degrees less then straight with the driveshaft. This allows for the axle rotation under torque. If the pinion is too high, it just goes higher, which will cause a vibration.

Rear pinion angle should be 1 to 2 degrees less then straight with the driveshaft. This allows for the axle rotation under torque. If the pinion is too high, it just goes higher, which will cause a vibration.

The axle on a TJ dont rotate like on a leaf spung vehicle. To the OP you want your axle pinion to point at the transfer case output. There is a picture on Tom woods website of what it should look like with a cv driveline.

The axle on a TJ dont rotate like on a leaf spung vehicle. To the OP you want your axle pinion to point at the transfer case output. There is a picture on Tom woods website of what it should look like with a cv driveline.

WRONG. Even in a linked rear there most definetly is still a small amount of axle rotation, its definetly not as much as a leaf spring rig but it is still there and needs to be accounted for none the less. It only needs to be 1* lower or so but it does need to be lower. If its straight at or slightly higher then the rear yoke then he will run into vibes. Also OP make sure your shaft is balanced.

WRONG. Even in a linked rear there most definetly is still a small amount of axle rotation, its definetly not as much as a leaf spring rig but it is still there and needs to be accounted for none the less. It only needs to be 1* lower or so but it does need to be lower. If its straight at or slightly higher then the rear yoke then he will run into vibes. Also OP make sure your shaft is balanced.

Please explain how with with upper and lower control arms and bushings that arent wore out how the pinion can rotate up then. Because I have mine set up with pinion on diff pointing directly at pinion on output shaft and guess what no vibes.

Please explain how with with upper and lower control arms and bushings that arent wore out how the pinion can rotate up then. Because I have mine set up with pinion on diff pointing directly at pinion on output shaft and guess what no vibes.

Simple explanation is that the rubber bushings allow for movement.

Please explain how with with upper and lower control arms and bushings that arent wore out how the pinion can rotate up then. Because I have mine set up with pinion on diff pointing directly at pinion on output shaft and guess what no vibes.

Good for you, have a cookie.

Every motor sport in the world that uses linked suspensions sets up their pinion angles 1* or so below. This is common knowledge and to argue it is almost pointless and would only go to show any ingnorance you may or may not have. Bushings wether poly or rubber flex, so does steel to a degree. The bottom line is it moves alitte and we still can't verify if the OP just "eyed" his pinion angle and got it wrong, it happens quite frequently, I know a few friends that tried eyeing it and its hard unless you have and angle finder or a driveshaft and a long straight edge.

I took it to a buddies shop with an angle finder and got the pinion dialed in to 1 degree below what the shaft runs at. And now I have slightly worse vibrations than before.

What in the world, this is just crazy??????????

This is on a 4 cyl. TJ with a 3" lift.

If that is the case, then I would be willing to bet that the CV joint is starting to go

Double check the U-joints. Did you check the balance of the shaft?