Driveline vibration after lift – How to properly diagnose?

Hi All,

I recently finished installing my 2″ lift – HotBits DT1 coilovers with ADF 2″ multi-link spacer kit and new OEM top hats, and I’m getting some driveline vibration (2008 XT, manual). The vibration occurs at ~35-45 MPH, in any gear. It is much more pronounced if I’m accelerating through that speed range. If I’m cruising at 40 MPH it has a kind of rhythmic amplification or harmonic oscillation (whummm whummm whummm type of sound, about a second apart from each other). There to be some similar vibration right around 60 MPH as well, but much less intense than the lower speed, barely noticeable. I thought driveline at first and fabbed up a couple of carrier bearing spacers, but that didn’t fix it. I think it helped, but certainly didn’t eliminate the root cause(s).

My understanding is that inner CV joints can exhibit this behavior, particularly after a lift. I’ve gone under the car and checked for play – There is some in both inner joints, 1/8″ or so.

I’ve also checked the driveshaft for play, at the front u-joint and carrier bearing. There’s a small amount of lateral play in front of the u-joint, not in the joint itself – output shaft bearing? There is also some play at the carrier bearing, but it just feels like the rubber is flexing, doesn’t feel like anything is actually “loose.” I’ll check the rear u-joint in the AM.

A few specific questions:

1. How much play, if any, should CV joints have?

2. How much play, if any, should there be at the output shaft bearing?

3. How much play, if any, should there be in the carrier bearing assembly? Should I be able to move it with light/medium effort (pushing/pulling from under car with one hand)?

4. How much play, if any, should there be at u-joints? As mentioned I don’t feel any there, and I don’t think there should be, but I’d like to confirm.

I think the only other things to consider are engine mounts, pitch stop, trans mount. – How does one verify that those are ok?

Anything else I should be considering?

Many thanks in advance for any advice!

Here’s a pic of the offending battlewagon :)


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