Tell us exactly what you are doing when you recorded this file. It sounds to me like I herd the door close and then the creeking started. I could not hear an engine running. Where did you have the microphone placed and in what direction was it pointing.

To me this sounded like and old Chevrolet with worn upper control arm bushings. They would make this noise when pushing up and down on a fender. Or when the front end dived during hard braking. The actual noise in the Chevy would be caused by a loose control arm shaft end cap washer bolt allowing the inner steal liner of the control arm bushing to slip and rotate on the stationary shaft. I belive the 560SL works somewhat the same way but instead of the control arm shaft, you have a seperate bolt going through each control arm bushing. If any of theses are loose slipping of the bushing inner steel liner will occure rather than the required torsion of the rubber.

Also I might add that just retigtening may not work because the inner steel liner sleeve has gripper teath at each end that tend to get worn off when this slipping starts. Those teath are there to prevent the slipping from occuring in the first place. Also an error commonly made by most service technichianns is that any or these type connections including similare ones that may be on the straring linkage like the idler arms of some cars, should be torqued with the vehical with weight on wheels and stearing wheel straight ahead. Very often these bolts are tigtened with the suspension fully extended which will decrease the service life of these bushings by putting a residual preload on them at normal ride height.

Can you get this noise to occure just by rocking the front end up and down?

Hope this helps

John Roncallo