My 2013 P85 has 23,000 carefully-driven miles. About a month ago I began noticing a clunking noise in the drive train when transitioning between regen and mild acceleration. With the windows down, I could hear it quite clearly when gently starting up from a full stop. This symptom seemed to match the classic drive train clunk that has led a number of owners to have their drive train replaced (under warranty of course). Apparently, in some cases the gear reduction unit has suffered premature wear due to the substantial torque load it has to handle, and this leads to some "play" in the drive train. Yesterday, I dropped my car at the Tesla service center in Watertown, MA to have this and a few other minor issues addressed. To my delight and surprise when I picked up the car, the clunk was not coming from the gearbox. Instead it was caused by the velocity joints on the driveshafts. They simply re-torqued the bolts on the velocity joints and the problem went away. This a further proof that an occasional visit to a Tesla service center is a good idea. They also performed a number of minor factory upgrades, many of which I was not aware of. Great car. Great company.