Purchased a 2013 cayenne porsche gts with 67k miles on it. noticed a kind of thumping sound when accelerating, usually appearing at 3k rpms. vehicle shudders and almost feels like the transmission is slipping. took the vehicle to a mechanic to diagnose the fault and they immediately knew what it was, engine transfer case failure. this is due to a design flaw allowing water into the transfer case that porsche is aware of and yet to address. on some occasions porsche will pay for the $5k repair but the part is still replaced with a transfer case with the same flaw. transfer case failure can lead to a sudden lose of power and potentially cause death or serious injury if someone is traveling at highway speeds. highly recommend addressing this with a recall for 2013 and 2014 cayennes. i have experienced sudden lose of power due to transfer case failure, neatly resulting in a highway collision.