Just received my 600 sl and after putting the car in reverse it was making a slight winding sound . Is this a normal ?

 

was it automatic or manual?

 

The car is automatic.

 

the transmission is automatic too?

common reason is that either there is excessive play in B3 (reverse multiple disc) or the thrust bearing in K1 making the grinding noise.

without actually hearing the noise, i cannot tell the exact reason.

in simple words, there must be an early sign of mechanical damage.