Torque exits the engine via a single-option seven-speed automatic transmission before heading to the wheels. Just which wheels provide motivational duties depends on which drivetrain option box you checked at the dealership. The standard configuration sends power through the rear wheels, but a $2,000 4Matic all-wheel-drive package splits power between the front and rear wheels. This is a permanent all-wheel setup with a default front-rear torque split of 45/55, but up to 70 percent of available torque can be temporarily shuffled to either axle as traction needs dictate.
The GLK’s transmission lacks a manual shift mode — there are steering-wheel paddles and its steering-column-mounted shifter only has stops for PRND — but it does feature two shift programs, Sport and Economy. The primary difference between these modes is that one (Sport) lets the tachometer sweep closer to its redline before shifting to take advantage of the available horsepower at higher engine speeds. Sport program will also downshift more readily when asked to accelerate and, occasionally, when braking in anticipation of a turn. The other program, Economy, short-shifts every gear, hustling to top gear as quickly as reasonably allowable to keep revs low and fuel economy up.
There’s also an Eco Start-Stop system system present on the GLK350 that will shut down the engine when the vehicle comes to a complete stop to prevent wasting fuel while idling. During my driving time, the system only seemed to activate when the engine was sufficiently warmed up, and the restart was smooth and effortless under most conditions. When restarting after sitting at a traffic light or stop sign, the engine would fire up in the time it took my right foot to ease from the brake to gas pedal and acceleration would resume without a hiccup. The only indicator that anything special was happening was a slight cough from the engine that you wouldn’t even really hear with the windows up and audio system playing. However, when the system started repeatedly activating during a stop-and-go traffic crawl, I became aware of a slight shudder that passed through the vehicle if I didn’t give the system time to do its thing. Fortunately, the button to defeat the Eco Start-Stop during conditions like that is handily located on the dashboard.