Thank you for your reply. The transmission does not make any sounds when shifting from N to D (i.e. it is only a delay in engagement). When shifting from D to N, I have tried with my foot hard on the brake padel and noticed a difference. The "tooug" sound is hardly noticeable.

I have also tried another S500 (2000) and noticed that it immediately engages when I shift from N to D unlike my S500 which takes about 2 seconds to engage.

With respect to the heat, I may not have been sufficiently clear on my post. I have not noticed any heat from the transmission. My reference to "heat" was intended to describe the vehicle's behaviour after driving it for a while.