1999 Mercedes-Benz SL500 Q&A

1999 Mercedes-Benz SL500 Question: a knocking sound underneath my car in cold weather. Tachometer is steady .

Knocking sound coming under the car, don't know where coming from, if the weather is warm or hot i hardly hear the sound, but in cold weather, the sound becomes louder.The knocking sounds only if the car is in motion, but on neutral idle no knocking sound . I have a mechanic check and he diagnose it need a new motor mount. is that true. -
Answer 1
very poss or drive shaft joint -