We've had out gl350 for about a month now and one annoying characteristic is the 2nd gear start. In cases where you need to quickly merge into traffic the truck require additional time to downshift into first gear. Unless to come to a complete stop, and wait 2-3 seconds the truck always starts in 2nd gear.
I've been unable to find any info about a sport mode for the transmission. Is this just an AMG feature??

 

Pull back left paddle at stop and starts in "1st" gear - then use right paddle (1) pull/hold right paddle two seconds to return to auto mode or (2) pull/hold right paddle 1 sec to upshift one gear.

Also understand in auto - at speed pull/hold left paddle 3 sec downshifts to power gear for that speed - very smooth to achieve passing gear or to add engine braking to deceleration - same procedure right paddle 3-sec/auto-return/1-sec-1-gear-upshift

 

So there is no "simple" Sport mode like on a BMW automatic. I tried out the proceedure above when merging into traffic and it was much better than the kickdown.