2015 XJL here with 110K miles on the odo. Last year, I hit a large pothole on the highway and ever since, I am chasing a shimmy/vibration I cannot seem to get rid of. The worst part is that sometimes the shimmy is visible and "feelable" at any speed, even at 20mph and other times it's completely still at any speed. Very annoying in otherwise awesome vehicle. I have since replaced all 4 wheels and tires (had them rebalanced twice), as well as all new brake rotors and pads. While the shimmy in the steering wheel got a little better, it's still there. Any idea what else may be contributing to this phenomenon and why it's not always there? Anything with steering? Nothing seems to be obviously loose or worn out and the wheel bearings are tight and quiet. I am really running out of ideas of where to look for further diagnosis. Thanks for any advice you can provide!

 

Greg,
Is there any chance that the ABS sensor/wiring loom has been damaged or either has been knocked loose? I chased a CEL (I know you haven't got that), on my old XK8 for nearly 2 years until I spotted torn insulation on the FR ABS cable.

I'm not saying that this is your problem, but it's worth looking at to see if the sensor cable was damaged.

wombat

 

Alignment been checked? I would suggest a wheel bearing but you say they are good, I have had them cause a very similar intermittent/cyclical vibration feel on cars that was super hard to find. Also lines up with happening after an impact.

If not that, I would go over all the links/ball joints/bushings in the suspension very critically, as something just a little off can present an issue under dynamic loading that doesn't show up stationary.

 

Check the banana arms on the front suspension. Have they been replaced? The bushings do go bad early on. Easy way to check them is to have someone watch the front wheel as you role forward slowly and apply the brakes. Have the observer notice if the wheel moves front to rear. If it does, replace the arms. Secondly, Did they put a dial gauge on the new rotors to verify if the runout was within spec. I had a brand new rotor out of the box that was out of spec and caused the same steering wobble issue I was trying to fix.

 

Agree with Freddy J!
Another vote for the "Banana" arms. Especially with the miles on the car. They are way over due! Don't forget to do the sway bar end links as well. The sway bar bushings are another wear/noise item to replace.
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Another vote for front "banana arms"
Inner bushes get softer by internal damage and then front wheels start to "fishtail" causing vibration for steering. Common issue of any brand using similar construction (exsample MB)

Edit: Lemförder is OEM and well available thru aftermarket channels.

 

Thanks for the suggestion, but since I do not have a CEL present and I could not see any issues with torn wiring, I don't think that's an issue for me. I am glad you found the culrprit, even if it took 2 years.

 

All great suggestions, which I appreciate very much. None of the front suspension components have been replaced as the car drives straight and tires wear evenly. Also, no clunking noises whatsoever, so I never thought it could be the banana arms, which I assume you refer to the lower control arms. That should not be too difficult or costly to replace, so I will definitely give it a go. I initially thought the wheel bearings could cause the shimmy, but they would have to be really worn severely to cause such a noticable vibration. I had to replace one of my rear wheel bearings at 90K miles and it was very loud and distinct but even then the wheel did not show any movement when checked upon lifting of the car. The front wheels roll very quitely, so again, I doubt the bearings would cause this. Another thought I had was possibly bent half shafts or worn out cv joints, but those would likely make clunking noise, which they do not. As it relates to the new rotors, they were not checked with a dial, but there was no difference in the shimmy between the old and new ones and breaking is smooth, so I don't think this is the issue. So, I think I will follow your advice and start with the banana arms and see if it makes a difference.