Drive line vibration after alignment

[Tknight6]

Hello everyone, I hope I've posted this in the right forum. It's a little lengthy but I wanted to post as much information as possible for you all.

I recently did a 3 inch zone suspension lift on my 99 wrangler and it came with a transfer case drop.

I installed the lift and adjustable front track bar. The gas tank was in the way of the rear track bar bolt and since I needed a fuel pump anyway I had a shop change the pump and install an adjustable rear track bar.

When I drove the jeep around before the shop did the rear track bar there wasn't any vibrations. For some reason they installed the rear track bar and my axle is not centered, now I'm getting some heavy vibration from 10-30 mph and it goes away. Could something like an offset axle cause this? Or would it always be something to do with the vertical angle of the drive shaft? Just to give an idea, the passenger side of the rear axle has about a half inch clearance between the rear tire and the shock, while the driver side has a couple inches clearance.

Thank you for your time

 

[Hopper]

Adjust your track bar to center and see if it helps.

 

[AndyG]

Hello everyone, I hope I've posted this in the right forum. It's a little lengthy but I wanted to post as much information as possible for you all.

I recently did a 3 inch zone suspension lift on my 99 wrangler and it came with a transfer case drop.

I installed the lift and adjustable front track bar. The gas tank was in the way of the rear track bar bolt and since I needed a fuel pump anyway I had a shop change the pump and install an adjustable rear track bar.

When I drove the jeep around before the shop did the rear track bar there wasn't any vibrations. For some reason they installed the rear track bar and my axle is not centered, now I'm getting some heavy vibration from 10-30 mph and it goes away. Could something like an offset axle cause this? Or would it always be something to do with the vertical angle of the drive shaft? Just to give an idea, the passenger side of the rear axle has about a half inch clearance between the rear tire and the shock, while the driver side has a couple inches clearance.

Thank you for your time

When your axle is not centered you are introducing another angle into the driveline and that could possibly mess with the elliptical cancellation that you need- Or you could have reached that magic lift height where you now need a CV shaft- There is more to it than that and we have some guys that can help you more than me I’m just kind of generalizing

You’re going to be OK it’s fixable just be patient and you’ll get it

Typically if you can post a good side picture of the driveline that helps.

 

[Vtx531]

The ujoints dont know if the difference is up or down or left of right but a couple inches in any direction would totally throw off the driveshaft angles.

To the mechanic - "you had one job..." (okay two jobs but still) I would loosen the bolts on each end and retighten them with the weight of the vehicle on the axles because the "mechanic" likely messed that part up too.

 

[Tknight6]

When your axle is not centered you are introducing another angle into the driveline and that could possibly mess with the elliptical cancellation that you need- Or you could have reached that magic lift height where you now need a CV shaft- There is more to it than that and we have some guys that can help you more than me I’m just kind of generalizing

You’re going to be OK it’s fixable just be patient and you’ll get it

Typically if you can post a good side picture of the driveline that help

Thanks! I'll get some pictures posted this afternoon hopefully.

 

[Tknight6]

The ujoints dont know if the difference is up or down or left of right but a couple inches in any direction would totally throw off the driveshaft angles.

To the mechanic - "you had one job..." (okay two jobs but still) I would loosen the bolts on each end and retighten them with the weight of the vehicle on the axles because the "mechanic" likely messed that part up too

Yes so the shop agreed to go back in and fix it. They were trying to make their alignment machine happy and were adjusting the rear axle trying to get it in tolerance. I asked them to just center the rear axle and not worry about it matching the front, if this doesn't fix it then I'll probably just buy some more washers to lower the transfer case a little more until I buy the SYE.

Thanks for your time.

 

[IJK]

Hello everyone, I hope I've posted this in the right forum. It's a little lengthy but I wanted to post as much information as possible for you all.

I recently did a 3 inch zone suspension lift on my 99 wrangler and it came with a transfer case drop.

I installed the lift and adjustable front track bar. The gas tank was in the way of the rear track bar bolt and since I needed a fuel pump anyway I had a shop change the pump and install an adjustable rear track bar.

When I drove the jeep around before the shop did the rear track bar there wasn't any vibrations. For some reason they installed the rear track bar and my axle is not centered, now I'm getting some heavy vibration from 10-30 mph and it goes away. Could something like an offset axle cause this? Or would it always be something to do with the vertical angle of the drive shaft? Just to give an idea, the passenger side of the rear axle has about a half inch clearance between the rear tire and the shock, while the driver side has a couple inches clearance.

Thank you for your time

The axle offset is just as important as the vertical angle. The u-joint don't know the difference between left, right, up or down, all the u-joint cares about is being in phase and not exceeding limits of angle. I would start by making sure that centerline of the engine/transmission and pinion are aligned using your adjustable rear track bar.

 

[Shawn at Tom Wood's]

What others have said is correct, your drive shaft doesn't know the difference between up, down, left, and right. What matters is the total angle. So if you are bumping right up against the limits of vertical angle and then you add a couple/few degrees of side angle you exceed those limits and develop a vibration problem. Usually things don't even have to be perfect to work well, just as close as possible. So don't freak out if you aren't able to achieve textbook perfect angles. All that being said, you were probably pushing the limits of vertical angle to the point of almost having an issue and the side to side angle put you over the edge. I think a slip yoke eliminator and double cardan shaft would be the best solution.

This second video is somewhat redundant to the first but also explains things in a little more detail.

 

[Tknight6]

Adjust your track bar to center and see if it helps.

What others have said is correct, your drive shaft doesn't know the difference between up, down, left, and right. What matters is the total angle. So if you are bumping right up against the limits of vertical angle and then you add a couple/few degrees of side angle you exceed those limits and develop a vibration problem. Usually things don't even have to be perfect to work well, just as close as possible. So don't freak out if you aren't able to achieve textbook perfect angles. All that being said, you were probably pushing the limits of vertical angle to the point of almost having an issue and the side to side angle put you over the edge. I think a slip yoke eliminator and double cardan shaft would be the best solution.

This second video is somewhat redundant to the first but also explains things in a little more detail.

Thanks! I am planning on getting an SYE eventually. Luckily they did what I asked and centered the axle and the vibrations are now gone.