Mack Trucks Adds 23,000-Pound Rear Axle and 325 Horsepower Engine Rating for Mack MD Series
Mack Trucks now offers a 23,000-pound rear axle and Cummins B6.7 engine with up to 325 horsepower on its Mack MD Series models. The heavier axle and suspension offer increased capability for hauling loads.

Mack Trucks now offers the new Cummins B6.7 engine and a heavier axle and suspension for its Mack MD.
Photo: Mack Trucks
In an effort to give Mack Trucks’ vocational customers improved durability and broader options for their applications, Mack now offers a 23,000-pound rear axle and Cummins B6.7 engine with up to 325 horsepower on its Mack MD Series medium-duty truck models.
Designed for a Gross Axle Weight Rating (GAWR) of up to 23,000 pounds, the heavier axle and suspension offer increased capability for hauling loads requiring the most durable trucks. The Mack MD with the 23,000-pound rear axle specifically benefits refuse packers with 11-yard up to 20-yard rear loaders and those Mack MD models being utilized as water trucks holding 2,000 to 2,500 gallons of water.
When paired with the 325-horsepower engine rating and the Allison 3000RDS transmission, the Mack MD is now capable of increased towing capacity if the customer has a trailer.
“The 23,000-pound rear axle expands the applications in the vocational market – with refuse and construction reaping the most benefits,” said Tim Wrinkle, Mack vice president of vocational and medium duty. “The 325 horsepower also offers carriers traversing longer routes or in a hilly or mountainous region a more durable and reliable powertrain. The rear axles on those truck models equipped with a dump body, hook lift or roll-offs take some abuse during the truck’s lifespan. The heavier axle rating has better durability, and the larger horsepower engine will provide enhanced performance.”
The Mack MD6, a Class 6 medium-duty truck model, has a Gross Vehicle Weight Rating (GVWR) of 25,995 pounds, and the MD7, a Class 7 medium-duty truck model, has a GVWR of 33,000 pounds. Both models are exempt from the 12% Federal Excise Tax (FET).
The Mack MD Series models meet the needs of trucking applications requiring dry van/refrigerated, stake/flatbed, dump, and tank truck vocations. The MD6 model does not require a commercial driver’s license (CDL) to operate for non-hazardous payloads.
The Mack MD Series is an all-new model range built specifically for medium-duty applications. Available in 4x2 configurations, the MD6 and MD7 models feature a sharp wheel cut for enhanced maneuverability for tough urban settings.
Updated Cab for the Mack MD
The MD Series cab was updated in January to a larger cab with a bumper-to-back-of-cab measurement of 107 inches, providing industry-leading comfort. Mack matched the bold look and styling of the Mack Anthem, Mack’s highway model, as a basis for the grille and hood design found on the MD Series.
Interior Features of the Mack MD
The interior boasts premium satin aluminum trim, improved seating with lumbar support and enhanced LED lighting. New steering wheel controls for cruise control, telephone and audio functions have been added, increasing driver convenience and safety. All of these have been popular with Mack’s Class 8 customers.
Mack MD Standard Safety Features
The trucks now come standard with several enhanced safety features, including new ABS (Anti-Lock Braking System) with ATC (Automatic Traction Control), radio mute in reverse, and a park brake alarm.
Easier Connections for Installations
Pre-wired body builder connections, relocated air dryer, and updated wheelbases to industry-standard cab-to-axle (CA) dimensions make the updated MD Series easier to install an even wider array of body installations than previously.
More Vehicle Research

2026 Ram 1500 Tradesman Put to a Real-World Fleet Test
A few days behind the wheel of a 2026 Ram 1500 Tradesman turned into a test of visibility, parking, work-ready features, and even severe-weather driving.
Read More →
Isuzu N-Series Gas Fleet Guide: Specs, Capability and 2027 Model-Year Updates
Explore Isuzu Truck North America’s N-Series Gas fleet specs, engine performance, GVWR and payload capability, configurations, chassis dimensions, work-focused features, and 2027 model-year information.
Read More →
Chevrolet Silverado 1500 Fleet Guide Specs Capability and 2027 Model-Year Updates
The next-generation 2027 Chevrolet Silverado 1500 brings new V-8 engines, updated technology, expanded safety features, and a fleet-focused Work Truck. Here’s what commercial fleets need to know so far.
Read More →
Ram ProMaster City Fleet Guide Specs Cargo Capacity and 2027 Updates
Work Truck’s Ram ProMaster City Fleet Guide tracks the latest specifications, cargo capability, configurations, fleet technology, pricing, and model-year updates for Ram’s mid-size commercial van.
Read More →
Ford F-150 Fleet Guide Specs Capability and 2026 Model-Year Updates
Explore 2026 Ford F-150 fleet specs, engines, towing and payload capability, configurations, work features, technology, and model-year updates.
Read More →
TCI Now Sells & Supports Battle Motors’ Vocational Trucks
Midwest truck dealer Truck Centers, Inc. (TCI) has expanded its transportation solutions with sales and service support for Battle Motors’ heavy-duty vocational trucks at locations in locations in Indiana, Illinois, and Missouri
Read More →
Ram 1500 Fleet Guide Specs, Capability and 2027 Model-Year Updates
Explore always up-to-date Ram 1500 fleet specs, engines, towing and payload capability, configurations, technology, pricing updates, and model-year changes.
Read More →
Peterbilt Trucks Equipped with Paccar TX-18 Pro Boost Efficiency for Maryland Fleet
Patuxent Companies is replacing aging trucks with the Peterbilt Model 567 and Model 589, specified with the Paccar TX-18 Pro 18-speed automated transmissions, and is reporting an 8% to 10% improvement in fuel economy.
Read More →
Stellar Expands into Fire Apparatus Market with Acquisition of Midwest Fire
Stellar Industries has acquired Midwest Fire, a custom fire apparatus manufacturer headquartered in Luverne, Minnesota, with nearly four decades of specialized apparatus experience.
Read More →
Recalls You Need to Know About in August 2026
If you have Altec, Chrysler, Ford, Heil, General Motors, International, Mack Trucks, Paccar, Rivian, Royal Truck, Toyota, US Truck Body, or Volvo Trucks vehicles in your fleet, you should check these important recalls issued by the National Highway Safety Administration.
Read More →
