A few days ago I have noticed that my car makes a metalic knock when pressing throttle while driving.
Its best noticable at around ~1500RPM when in 3, 4 or 5th gear when I press throttle gently after not pressing it fow a few seconds (braking with engine).
Its like some kind od play is canceled and then a metal to metal slap is heard.
I have checked read diff mountings and thay are ok.
What can be the couse of this ?

 

Jack the car and with it in gear, check the free play at the wheels. Also the free play at the prop shaft. Obviously, there should be some play, but excessive play could indicate a problem in the diff. I had this on my old 99MY when it was only 1800 miles old! It meant a new diff under warrenty.
JohnD

 

I rised one rear wheel of a car, released hand break and left the car in 1st gear. Rocked the wheel front to back and there it is a slap/knock comming somewhere from gearbox area.
Is this a center differencial problem ? When rocking front wheel with rear wheels on groud and hand brake engaged I dont hear that sound.