HMPT 800

RENK America, the Muskegon-based subsidiary of German defense giant RENK Group AG, announced June 26 that the Army Contracting Command at Detroit Arsenal had awarded the company a new five-year production contract for its HMPT 800 hydromechanical transmission. The deal is the fourth consecutive multi-year contract in the same series, meaning the Army has now continuously renewed this relationship through four award cycles, a track record that speaks to both the transmission's performance record and the absence of a domestically competitive alternative at this weight class. RENK America says it has delivered more than 4,500 transmissions since the program began under the THOR partnership, which stands for Transmission Heavy Off-Road, the Army's original contracting framework for medium tracked vehicle drivetrains. The HMPT 800 is not a minor component. It is the drivetrain heart of armored vehicles weighing up to 45 metric tons (99,000 lb), paired with engines producing up to 800 horsepower, and it handles everything from smooth highway movement to the jarring cross-country mobility demands of tracked combat vehicles. The AMPV, the Army's most recently fielded armored platform, runs a Cummins VTA903E-T675 diesel engine rated at 504 kilowatts (676 horsepower) bolted directly to the HMPT 800, giving the 36-metric-ton (79,400 lb) vehicle a top road speed of 61 km/h (38 mph) and an operational range of roughly 362 km (225 miles). Without that transmission functioning reliably, the vehicle does not move, regardless of how much armor, electronics, or weaponry sits above it. The Bradley Fighting Vehicle, the workhorse of the Army's armored brigade combat teams for more than four decades, has depended on the HMPT transmission family since its introduction in the early 1980s. The original Bradley used the HMPT-500, a hydromechanical automatic transmission developed under contract to the Army's Tank Automotive Command that had, by 1999, been built in quantities exceeding 11,000 units for domestic and export customers. The HMPT 800 represents the next generation of that lineage, scaled up to handle heavier platforms and more demanding power inputs while preserving the same basic interfaces — a design choice that simplified integration into new vehicle programs without forcing wholesale drivetrain redesigns across the fleet. The AMPV program, which began full-rate production in 2023, is the primary growth driver for the HMPT 800 going forward. Designed by BAE Systems on a Bradley-derived chassis, the AMPV exists to replace the ancient M113 armored personnel carrier, a vehicle that entered service in the early 1960s and proved dangerously vulnerable in the urban combat environments of Iraq. The AMPV comes in five baseline variants covering troop transport, medical evacuation, medical treatment, mission command, and mortar carrying, with BAE Systems expanding the family at AUSA 2025 to include additional configurations featuring counter-drone turrets, remote 30 mm cannons, and autonomous driving packages. Every one of those variants runs the same RENK transmission, meaning the HMPT 800 production line in Muskegon sits at the supply chain chokepoint for the entire program. "Readiness begins with a resilient and responsive industrial base," said Corey Johnson, CEO of RENK America, in the company's announcement. "This award reflects the trust placed in our team and our proven ability to deliver the HMPT transmissions and support our customers need to sustain the fleet. Every transmission we deliver contributes to the dependability and availability of the platforms that our Warfighters depend on around the world." The XM-30 Mechanized Infantry Combat Vehicle, the program intended to eventually replace the Bradley, achieved Milestone B approval in June 2025, with prototype vehicles from competing industry teams slated for delivery by the fourth quarter of fiscal year 2026. That program remains years from fielding, meaning the Bradley and AMPV will carry the load for the Army's armored formations through the remainder of this decade and into the next — and every one of those vehicles will continue to need the transmission that RENK America builds in Michigan. The fourth HMPT 800 contract is, in that sense, less a routine procurement action and more a deliberate investment in keeping the current fleet viable until its eventual successor arrives.

HMPT 800

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HMPT 800

RENK America wins fourth Army transmission contract, worth $691M

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About The Defence Blog