Originally Posted by Threxx

Right, well how many 5-speed autos do you see running as dedicated drag racing cars? Exactly. So this is a compromise between the two.

There comes a point of diminishing and even negative return based on gear ratios and torque output. Take an extreme example. If you had a road course car with a 10 speed automatic and .15 seconds lock to lock shift time then you've spent about a full second and a half wasted being out of the throttle moving from a stop to top gear, not to mention any shifting done inbetween.

Say a 5-speed automatic with the same shift time... instead you have around 3/4s of a second wasted going through the gears once.

Question is, will that beast of a motor really benefit that much from the gearing advantage to make up 3/4 of a second or more per full run through the gears?

The question is often no, especially when dealing with vehicles that have very high torque ratings ultra-flat power bands (as is the case with these mercedes that are typically torque rated from 1700 to 5500 rpm or so). They just don't benefit THAT much from shifting into the next gear at 4700 RPM vs 4000 RPM because they make just about as much power at either RPM, so then you only get the minor benefit of slightly improved torque multiplication of a slightly shorter gear.