My 10 CGTS is at Porsche for the passenger seat weight sensror repair. Since it was there I asked my SA to perform a thorough inspection aka PPI. Their tech determined the driveshaft bushing and horn required replacement. Is this the "Cardan" driveshaft problem often referred to on this and other sites? I'm still under OEM warranty so I'm not worried. My SA said the bushing replacement alone is $1,700.

 

If he is referring to the bearing support, then yes. If he is referring to the flex disc then no, althought the Pcar is also known to have flex disc issue too.

The driveshaft problem:
The two parts of the shaft (rear and front) are mated togehter with a joint. At that location, there is a bearing with a support brace. The bearing is surrounded with a damping rubber. When mounted in a car, the bearing support brace keeps the shaft centered so that it does not wobble when driving.

When the driveshaft failure occurs, it is usually due to the bearing bushing wearing out, causing slack on alignment between the two parts of the shaft.
With that slack, when accelerating, one will feel a strong wobble (sometimes violent) as if there was a very off balance wheel under the center of the car (where the joint is).
Worst case, car is disabled and needs towing to get fixed. Otherwise, it is good to drive it home gently and park until parts replaced.

I just went through this, and am preparing a DIY so that others can have easier time replacing. Not hard but time consuming with a few small tricks.

If you choose to go with shop replacement, it usually costs around what you were quoted. Since you are in warranty, get them to replace for sure.
If you choose to do it yourself, it will cost about $400 including parts, as long as you have time and a place to do it (garage and half a day if not working on cars much).

 

Based upon your excellent feedback I called my dealer to ask more questions. Although it was wearing it's the same Cardan problem discussed in earlier emails. This is the first pending failure they've seen in a newer Cayenne. I hope this isn't a harbinger of things to come!

 

since you are under warranty, I would not worry at all.
All cars break, after all, they are mechanical things, and without proper maintenance, that eventuality will arrive sooner or later.
Shaft issues on Cayennes were a problem for 1st gen, and were supposed to be resolved. Mind you, the issue may reside in the way the parts were put in as well (since one has to center the bearing bushing properly so when shafts rotate, they do not cause excessive wear on the bushing and bearing). So in all, time will tell if this will be a problem for your gen of Cayenne. Regardless, they are awesome cars, and even if they do break, it just wants you to drive them all that much more after you get them back from repair.