Explore the Latest in Truck Culture

NQH is GM’s two-speed electronic Autotrac transfer case — the rotary dial with an AUTO mode. It is also the transfer case named in GM’s own Service 4WD bulletin.

GU5 is a 3.23 rear axle ratio — the tallest common gear GM puts in a full-size truck. Best empty-truck economy, worst tolerance for a tire upsize.

GU6 is a 3.42 rear axle ratio — the most common gear GM builds, and the one NHT lists. Why it became the default, and what it costs you on bigger tires.

GT4 is a 3.73 rear axle ratio — the working gear. Every record we hold, 2000 to 2026, says 3.73. What it does to cruise rpm, towing and bigger tires.

G80 is GM’s locking rear differential — but it has not meant the same hardware for fifty years. Positraction on a 1973 C10, an automatic locker on a 2026 Silverado. Here is every year we hold a GM document for.

NHT is GM’s Max Trailering Package. On 2021 trucks the factory documents put it at an 8,200 lb max-tow rating with a 9.76-inch rear axle.

Z82 is GM’s trailering package. The factory documents list a Class IV hitch and 11,000 lb capacity on 2016–2018 trucks — here is the full picture.

Z85 is GM’s standard handling and trailering suspension. If your label has Z85 and not Z71, this is the truck you have.

VYU is GM’s Snow Plow Prep Package. GM’s 2016 special-applications document lists all ten components — spring rate, oil cooler, alternator and more.

Z71 is GM’s off-road package. What it actually includes changed with every generation — here is what the factory documents say, year by year.