(early GM 3L80) or 4-speed automatic (later GM 4L80E). Transfer Case
The Humvee was designed to climb 60% grades, traverse 40% side slopes, and ford deep waters. It carries heavy armor, weapon systems, and troops. To achieve this, the engine needed massive low-end torque to turn massive gears at low speeds. It didn't need to go fast; it needed to go everywhere .
Surplus 6.5L Humvee motors are widely available on Government Liquidation, eBay, and specialty dealers like Hummer Parts Guy (HPG) or Kascar Real4WD.
Replacing the Humvee motor with a non-Detroit engine may ruin the vehicle’s fording depth (the stock 6.5L has a sealed waterproof distributor on the injection pump) and military collector value.
A slight bore/stroke increase to 6.5L. Power rose to about 160 hp and 280 lb-ft. Still slow, but slightly less so. The real revolution came with the turbo.
