The Duramax is paired with a heavy-duty six-speed automatic transmission supplied by Allison. All models can be ordered with the Trailing Equipment Package, which includes a hitch platform, wiring harness and integrated trailer brake controller.
To fit its many work roles, the HD 3500 comes in three cab styles: regular (three-person bench seat), extended (adds a rear bench for six-person seating) and crew (seating for six with four doors). Crew cab models carry a standard 78.8-inch rear box, while the others get an extended 97.8-inch box. The HD also comes with no box at all, making it the ideal platform for RVs and commercial vehicles. Dual rear wheels are available across the board.
The base WT (Work Truck) is all-business, right down its black rubberized floor covering and painted steel wheels. You do, however, get air conditioning and a stereo, and carpeting is available. The LT is more consumer-oriented with premium cloth seats, power windows and locks, MP3 and CD, and most other conveniences found in passenger cars. The line-topping LTZ—not available with the regular cab—adds front leather bucket seats with power adjustments, Bose speakers, aluminum interior trim and other luxuries. Fully equipped, the LTZ's interior rivals those of luxury SUVs.