… which is an XF question and not an XK question but NO ONE seems to know, so I need the help of the Brain Trust.

About 500 miles ago I did hit some pretty severe, bone-jarring potholes and developed some vibration issues(the car, not me…).

I’ve had good luck with my Jag dealership here in Boston (and I believe through their loaner policy I’ve driven ever car in the Land Rover line), so I brought it in. They did an extended highway test drive. We decided:

- all new tires (conti extreme contact DWS 06)
- pads and rotors all around (yes necessary. I’ve put 55,000 miles on the car, which I bought used, and never did any brake work. It was time, and what the hell.)
- straightened and refinished two rims.
- balanced all tires
- alignment.

sooo… first long trip at highway speeds (65-85)… I got vibration. Symptoms:
- no issues below 50-60 mph.
- vibrations (felt in steering wheel) most noticeable on acceleration, like when passing on the highway. Could be imagination, but seemed strongest when passing under load (up a hill)
- if I crested a hill, put car in neutral and coasted, symptoms mostly go away.
- also, symptoms seemed to get more noticeable after like 1/2 hour of driving. (Not 10-15 minutes, which is odd to me.)
- no codes.

in other words, if I only did short drives near home I’d think the car ran perfectly. The issues are only under highway conditions and become more pronounced after 30-40 miles of fast driving.

Keep in mind this is an all-wheel-drive car.

the dealerships only suggestion is either straighten the wheels again or replace them. But that doesn’t seem right to me and I don’t want to throw any more money at the problem without a good idea.

Any and all thoughts most appreciated.

 

Prop shaft(s)?

 

I bought a car one time, and when I went to pick it up and drive it home, it rode great below 60, but above 60 it shook like crazy. Took it back, and they found that they didn’t balance the wheels before they swapped them in (I knew they were going to swap the wheels before I bought it).
I’d suggest taking to a shop that does Road Force Balancing (I’ve had good luck at Discount Tire). I had an issue once, took it there, and they showed me the spinning wheel/tire on the machine, where you could clearly see the wheel ran true, but the tire was ‘out of round’.

 

good idea. Another person mentioned motor mounts, of all things. But the way they described it— if one is fine and the other is shot, the engine might vibrate on acceleration— it kind of makes sense.

queation: is there a visual/diagnostic way to assess the shafts? Or is it road test only?

 

Another common weakness are the front banana links. Worth checking that these are not worn.

 

Some shops have a 'vibration detector' or something like that, it shows the frequency of the vibration at each given speed. That can narrow it down to a specific area because of the RPM of all the different pieces are different at each speed.

 

Only when hot. Only over 60. Feeling is in the steering wheel...
I'll bite;
1st guess: actual steering system? Let's start with the easy path, how many miles on the ball joints? on the fluid? Is the steering rack and hosing dry?
2nd guess, an out of balance or aligned wheel/tire?
3rd guess, a bushing or bearing?

Is there a prize for the right guess?
Cheers

 

You can try checking the motor mounts with a little help. Open the hood and have someone rev the engine. If a mount is shot on one side, the engine will lift a bit. Easy to see.

 

I think if it were still the (new) tires, hubs, or suspension, the vibration wouldn't go away when coasting at speed. When a vibration does go away when coasting, it is usually the drive shaft or the transmission. Unless it was one heck of a pothole it is unlikely to have damaged the transmission so I'd wonder about driveline alignment.

 

Thanks all. This has been VERY helpful. Couple more details:

— car has 92,000 miles.
— I have driven it cross country three times. Last at about 78k miles. Drive was rock solid, no vibration. And if you’ve done the west (NV, UT, CO, etc) you know that you can spend a LOT of
time above 90mph.
— there is no vibration felt in the brake pedal.
— HELPFUL: vibration def more noticeable on downshift/higher RPM. I’m at 1800 rpm at 70 mph. I push it to 80, car downshifts, rpm 2500,
MUCH more noticeable.
Again, almost unnoticeable below 60 mph but really frustrating at higher speeds / rpm

 

Also if it was not clear: virtually new tires. (But the last time i brought it in they noticed an “unusual wear pattern” on the rears and swapped them
out. And they were new-ish. Continental is good that way) full balance and alignelent at that time, which was less than 1000 miles ago. The car should ride like a magic carpet now.

 

Last two things:
I’ve already had the motor mounts replaced under warranty. Maybe good… or maybe it’s just an issue with this car?

I’m doing all this because otherwise I LOVE this car.

 

hmmm… wear pattern on the ***-end…. How does your alignment report look? How are the bolts and bushings for the front and rear subframes?

Truly, at elevated speeds, there are elevated stresses on all components. I may be wrong of course, diagnosing from afar, but it still sounds like suspension related to me.
Though interesting none of us is thinking axles or diff related. Cee Jay being the closest with prop joints.

 

Sorry for the long delay but this was finally resolved about a month ago so I thought I’d offer an update:

- took the car to jag of Boston one more time. They did a fancy “road force balance” one more time, claimed it was “90 percent better” and claimed 100 percent it was the tires, and that they’d been havin issues with continentals lately. Which sounded odd to me.

- drove home (120 miles). Issue was, if anything, worse. SO frustrating.

- took it to a high-end European place here in the Berkshires in western MA (autobahn, highly recommend). They drove it for like three miles and determined it was NOT the tires.

- replaced both front CV joints (or whatever they’re called on these cars). They the left one was damaged, and yes likely due to impact. They said to be on the safe side best to just replace both fronts at this mileage (at this point the car was just over 100,000 miles). I agreed.

- So, $4000 later, problem solved. Which is deeply disappointing given that I’d brought up this issue to Jaguar of Bost multiple times while the car was under CPO warranty and this work was done just after the car was out of warranty.

Anyway, thanks for your input. My lesson: trust your gut, and your experience. I knew from day 1 that the tires were not the issue.