Normal performance figures like acceleration, top speed, and even fuel economy fall away once you enter the realm of heavy-duty full-size trucks. In this playing field, there's only two important metrics: torque and towing.
Let's take a minute to talk about the two sacred Ts. The 6.0-liter gas engine can muster up to 380 lb-ft of of torque, but that's ho-hum compared to the eye-watering 910 lb-ft of twisting force that the 6.6-liter turbo-diesel can pump out. This translates to a maximum towing capacity of 18,000 pounds for the oil burner, while the gas motor can drag up to 13,000 pounds aft of the tailgate. Both engines utilize a six-speed automatic.
The Sierra doesn't disappoint in the payload department either, even if the raw numbers aren't as astonishing to behold. The top payload rating is 3,233 pounds, possible in gas-powered Crew Cab, 2WD, standard-length bed format. The lowest payload is a relatively paltry 2,356 pounds, which is the max rating for a diesel Crew Cab with 4WD and the eight-foot bed.
Underneath the Sierra's bed lies a tried-and-true leaf-spring suspension, which does an admirable job of maintaining a pleasant ride for when the truck is hitched up or fully laden. Empty the bed or unhitch your trailer, and the lack of refinement from this old-school design becomes apparent, making you question why the air-spring suspension in the Ram trucks isn't more widely plagiarized.