[Porsche 951 Fanatic]

Ok dont take my word for it but MABEY the cv joints are worn and the chunk is them reaching the end of there play.... and perhaps when you are going quick when you shift you most likley go from a high rpm to where the engine is idling and it has to kick back up when you disengauge the clutch and it uses the power from the wheels to speed up the engine. so i could be wrong though... does it make noise when your turning? or say when its stopped and in gear without the motor running can you push it back and forth a bit? i dunno.. all i can say is good luck and i hope i was of some help. Peace