I got this problem with my car where buy there is this knocking sound as i drive. The sound only is heard when you are in the car and engage drive and the knocking begins. If you put neutral the sound disappears or when on drive and u release the accelerator the knocking stops. It gets louder when you driving on a hill or turning right. At high speed you can hardly hear it. My mechanic has changed the CV joints, checked the bearings,brake disk,changed the bushes, the drive shaft is not touching anything, nothing is broken, and my mechanic finally told me go to Toyota Kenya.
So is anyone with a clue whats wrong with my car, thou it drives on well, but am afraid something huge may brake down as time goes on.

Kindly help.

gear box related most likely - if automatic suspect the torque converter.

the best place to check is the boot . make sure there are no to people knocking boots there . lol

Thanks for your response, actually there are no oil leaks anywhere in the engine. The oil filter is intact no leaks neither.

Check the exhaust system, the exhaust might be loose and/or has left its normal line setting. When you engage the car it vibrates and hence the noise, when at high speed the car is steady and there is less vibration and less noise.