Grinding noise under heavy acceleration - 407SW HDi

[Harshan]

been enjoying the heavy torque of my "new" 407SW for awhile now. All of a sudden, this morning it gives a grinding sort of rough sound when accelerating hard from standstill. Sometimes it comes while the car is on the move and if kick down to speed up suddenly (i.e for overtaking). Frequency of the sound is low (noise it loud) at the beginning and increases (noise level goes down) and when the torque reduces, the noise disappears. Could've imagined the dual mass if mine was manual. But it's 4HP20.

wondering what could be the cause before taking it to agents to avoid a rip off.

Really appreciate any thoughts, experience to shed some light.

[Doggy]

I would start my checking the engine & gearbox mountings - if they allow the power unit to move more than usual you may get more sound/vibration transmitted to the body.

On 406's you can check by trying to rock the engine backwards and forwards, (407's probably the same). You shouldn't be able to move it more than a millimeter or two.

[Harshan]

thanks doggy. I was panicked that i might've killed the gearbox and troubling goo gol too much till it wanted to retire early.

after posting this, went back to garage with a flash light and did all sneaking, peeking within my limits and found that the left engine/gearbox mount is knackered.. need to find the part now..