AM General Hummer H1 VIN Decoder

Every civilian Hummer H1 built by AM General LLC between 1992 and 2006 carries a 17-character Vehicle Identification Number that follows the ISO 3779 standard, but with a manufacturer-specific layout unlike almost any other passenger vehicle on the road. Decoding an H1 VIN can confirm the engine and transmission actually fitted to the truck, distinguish a civilian model from a fleet/government unit, verify the GVWR class, and pin down the model year and assembly plant — all useful checks before buying a used H1 or matching parts to your specific configuration.

AM General used a single WMI, 137, for every Hummer H1 it produced, so any VIN starting with those three characters can be confirmed as a genuine AM General-built vehicle. From there, the VIN departs from the typical passenger-car format: instead of a vehicle-line code in position 4, AM General placed the engine code there, followed by the transmission in position 5 and a two-character body/series code in positions 6–7 — a layout closer to what you'd see on a commercial truck or military vehicle than a consumer SUV.

AM General is a US defense contractor best known for building the military HMMWV (Humvee) for the US Army, and the H1 is the civilian version of that same vehicle — sharing its body-on-frame chassis and portal axles, which gives it unusually high ground clearance for a street-legal vehicle. It should not be confused with the Hummer H2 or H3, which General Motors built on its own platforms after acquiring the Hummer brand name, or the modern electric GMC Hummer EV launched in 2022 — neither of those vehicles uses WMI 137 or was built by AM General, and this decoder does not cover them.

Start with the WMI in positions 1–3: 137 confirms an AM General-built Hummer H1 manufactured in the United States. Position 4 identifies the engine — for example D = 5.7L V8 gas (GM 350), F = 6.5L turbo diesel (GEP), P = 6.6L Duramax diesel (later Alpha models), W = 350ci V8, X = 6.2L diesel, Y = 6.5L naturally aspirated diesel, and Z = 6.5L turbo diesel. Position 5 gives the transmission paired with that engine: A = 4L80E automatic, E = 3L80 automatic, or H = Allison 5-speed automatic (used with the Duramax/Alpha engine). So a VIN beginning 137P...H... points to a late-model Duramax diesel H1 with the Allison automatic.

Positions 6–7 are a two-digit body/series code that also tells you whether the vehicle is civilian or fleet: civilian codes include 82 (2-door VLC2), 83 (4-door HMC4), 84 (Wagon HMCS), 85 (open-top HMCO/VLCO), 90 (hard-doors HMCO), and 91 (slantback HMSB), while 55, 56, and 57 indicate military/government fleet K-series vehicles rather than civilian retail H1s. Position 8 is the GVWR class (3 = Class 3, 10,001–14,000 lb), position 9 is the standard ISO check digit, position 10 is the model year using the standard 30-year letter/digit cycle, and position 11 is the assembly plant — E for AM General's main plant in Mishawaka, Indiana, or U for Livonia, Michigan. Positions 12–17 are the production sequence number unique to that vehicle.

Because AM General's VIN layout is not documented by NHTSA in the same public databases used for mainstream automakers, the position meanings above are compiled from AM General/Hummer technical references rather than a federal decoder feed — always cross-check against the vehicle's build sheet, dealer invoice, or a trusted Hummer specialist before making a purchase or parts decision based solely on the VIN.