Choose the model years that match your GMC Sierra 3500HD.
2018 GMC Sierra 3500HD6.6L Duramax L5P turbo-diesel V8 with the Allison 6-speed automatic (2500HD/3500HD pickups). Taken from GM's 2018 Duramax Diesel Supplement, which covers diesel-specific items; for other chassis items such as brakes, cabin filter and tires, see the regular 2018 Sierra owner's manual. Gas-engine Sierra HDs are not covered.