Car vibrates bigly at 65+ and it gets more pronounced the faster you go. I had all the tires replaced with Michelin P4AS but the vibration remains. It doesn't vibrate all the time either - sometimes it does and sometimes it doesn't. I am thinking it's UCA/LCA bushings, but I put the car in the air and checked them and they're not leaking. I am suspicious of something in the rear suspension because I really feel the vibration in the seat - not the steering wheel. Any ideas?

 

Do you have any spacers? If you didn’t have this before tire change it could be a bad tire or bad balance job or water in the tire from a bad air compressor

 

No spacers and they're OEM wheels. This vibration started out of nowhere, too. No impacts or curb hits. I had the old tires road-force balanced and they all balanced out fine according to the machine. The vibration was still there after the old tires were replaced and road-force balanced, too.

 

If all wheels and tires road balanced then look elsewhere…put in clutch when vibration is present to eliminate engine as problem…check your drop links as they can come loose from factory…is the vibration at a certain rpm in all gears or a specific speed regardless of rpm?

 

Thanks for your reply. I put the car in neutral when the vibration happens - no change. I'm leaning towards front end bushings at this point.

 

Have you inspected your engine mounts and transmission mounts for cracks or excessive wear?

 

Does stepping on the brake change anything? If it does, sounds like a bushing problem.

 

We had a poor control feeling and the upper control arm was the culprit. It's next to impossible to visually inspect the bushings. They don't need to look bad to be bad. How many miles has it been since you changed the UCAs, or how many miles on the car if you haven't ever? It seems the 20" wheel option takes their toll on the UCAs by 50k miles....

 

Car has 62k. It's currently at the shop for a once-over to get to the source of the problem. They found that the rear flex disc at the diff was cracked, so they're replacing that. They also said it is not the UCA/LCA bushings, but that was my first suspicion too.

 

The worn bushings at least of the UCA did not leak any fluid, but were cracked. No fluid inside. Don't know about the LCA bushings...

 

Maybe if you lift the car and grab the wheel and try to shake it you may be able to determine if the bushings have failed.

When we had it at the shop for the front right strut failure/leak the tech showed me the upper control arm. All he did was lift it a few inches. Upon letting go the arm moved back down to the initial spot due to looseness. That was all that was needed to determine it needed replacing. (He did ask/verify with me that there is a noise upon compression/bump in cold weather).

When I replaced the front left I knew just from the fact the front right needed changing a little while before that this was the likely culprit. Symptom was lack of stability/control when driving at freeway speeds.

(Hope this helps)!

EDIT-. Does the car vibrate at a standstill?
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Update: Took the car to a shop. They said the vibration is due to a bad driveshaft isolation bushing (AKA "guibo"), where the shaft connects to the diff. Honestly, I kind of suspected something in the rear end of the car because I could feel the vibration in my seat long before I felt it in the wheel. They also found a leaking vacuum pump and a leaking cam cover, leaking trans pan seal, and a bad driver's side engine mount. Total bill $7,200, warranty is covering $6,200 or so. Could be worse.

 

Closing the loop on this - it was definitely the guibo. Porsche said that they had to replace the entire driveshaft assembly, which they did - but the vibration is gone.
Edit: Took the car up to 75 today and it felt like it was going to pitch a wheel into space.

 

Glad you have it resolved!

 

Some good info on the flex disk coupling (guibo).

https://www.eeuroparts.com/blog/driv...ce-your-guibo/

I had one starting to fail on a MB S600 I used to own. In high horsepower vehicles I really think it is a "consumable" part after 75-100K miles. (lots of discussion on MB forums on about this part)
It is on my list to visually inspect on the Panamera at next oil change. (never looked at it in detail)

Usually a pretty easy DIY fix if you access to a lift (at least on other vehicles).

Glad it solved your problem.