SL500 R129 Knocking noise??

[FSL500]

Hello,
On my 2001 30K mile SL500:
When starting from cold the engine runs at higher revs for 10 seconds then smooths out to 'normal' speed -OK.
Engage DRIVE and move off and for the first 30 seconds to 1 minute I get a 'knocking' that (maybe) sounds like a dry pump trying to prime itself - maybe 2 beats per second. The noise then disappears and all is fine for the rest of the day.
I believe it may be linked to gearbox or steering as the car does NOT make the noise if just left ticking over in the garage from a cold start.
Any first time ideas anyone please before we start a more serious (maybe expensive!!) hunt?
Thanks,
Frank

 

[Sp!ke]

This is indeed a weird one.

It could be the power steering pump if it doesnt make the noise when turning but I would imagine the pump would make a groaning noise rather than knocking and I cant quite fathom why it would make the noise only in Drive.

If its the gearbox making the noise and the noise dissappears when turning left, my initial thoughts are low oil levels.

I'm just wondering if all the belts are in good condition and not showing any signs of deteriation.

I strongly suggest getting it properly looked at asap and to refrain from driving it if possible until the source of the problem is found for fear of causing some serious damage.