I had a similar intermittent rumble which became very bad last weekend....
Got the car into a fantastic independant Porsche specialist on Monday, inspected car and my Cardan-shaft had split in the middle....
£623.00 for the part from Porsche and total bill including part, labour & vat from independant £832.00....
I'd have the cardan-shaft checked, common failure on Cayenne's, thankfully the new shaft has been modified by Porsche so shouldn't fail.... Time will tell....
Got the car into a fantastic independant Porsche specialist on Monday, inspected car and my Cardan-shaft had split in the middle....
£623.00 for the part from Porsche and total bill including part, labour & vat from independant £832.00....
I'd have the cardan-shaft checked, common failure on Cayenne's, thankfully the new shaft has been modified by Porsche so shouldn't fail.... Time will tell....