Mack Trucks introduces the Mack S852, an 85,000-lb. GAW (gross axle weight) rating of its proprietary tandem drive axles. The new rating comes as Mack celebrates 120 years of drive axle design, engineering and manufacturing this year and highlights its iconic Mack S-series axles and C-series axle carriers. The Mack S852 is available for order now.
“Mack has a long and rich history of engineering and manufacturing its own powertrain components, including drive axles, as it fits with our philosophy that components designed to work together, simply work better,” says Roy Horton, Mack Trucks Director of Product Strategy. “We welcome the new S852, which will broaden the applications our trucks are built to handle.”
Customers in Mack’s export markets expressed a strong interest in the new rating, where local applications require a heavier-duty axle. Customers in North America will also be able to spec the 85,000-lb. rated axle for specialized severe-duty or heavy-haul applications on Mack Granite models. For extreme loads at slow speeds, the S852 tandem drive axles have a creep rating of 105,000 lbs.
The new S852 pulls from a long history of Mack drive axle expertise. The very first Mack drive axles were found on the original Mack bus model built by the Mack Brothers Company in 1900 that transported sightseers through Prospect Park in Brooklyn. After operating in Prospect Park for eight years, the bus was converted into a truck and continued operating until 1923, accumulating more than one million miles.
A major advancement in Mack axle design occurred in 1920 with the introduction of double-reduction architecture. This unique design maximizes durability by reducing the speed from the drive shaft before transmitting torque to the axle shaft, as well as helping spread and balance loading over two gear sets.
Today’s modern Mack proprietary drive axles are also engineered with a double-reduction design and include several design advantages implemented through continuous research and development efforts.
One such design advantage is the use of Durapoid bevel and helical gears. This design provides favorable gear tooth geometry that helps eliminate localized stress and loading on the gear tooth end, providing enhanced strength and longer gear life. Frictional losses are also reduced in this gear design, allowing Mack axles to deliver up to 1.5% improved fuel efficiency.
“Low-traction situations can be a challenge for truck drivers, seriously impacting their productivity,” says Horton. “To help address that issue, we offer standard inter-axle and optional inter-wheel power dividers that automatically distribute torque between the slipping and non-slipping axle or wheel respectively. This elegant engineering solution is proven and reliable and requires no intervention from the driver.”
Mack proprietary axles also feature a top-mounted carrier design that is not only less prone to main seal leaks, but also provides more than two inches of additional ground clearance. This gives customers improved maneuverability at construction sites and other off-highway applications.
An additional benefit of Mack’s top-mounted carrier design is improved driveline angles between the drive axles. Instead of a three and a half to eight-degree angle, Mack’s prop shaft angle is just one to two degrees. This maximizes universal joint life, allows for greater axle articulation and reduces vibrations for a smoother ride. It also reduces torque losses for improved efficiency.