A New Transmission for Ram HD Trucks

Ram HD trucks have built their reputation thanks to a key ally: Cummins engines. Since 1989, Ram (Dodge at the time) has shared this commercial-grade engine with several industrial vehicles.

Thanks to this proven powertrain, Ram HD trucks have earned a strong reputation for durability, regularly covering hundreds of thousands of kilometers—even millions. The limiting factor of this exceptional engine was more on the transmission side. Since 2007, Ram had been using an Aisin unit, the 68RFE, which demonstrated a certain level of longevity, though it never quite matched that of the Cummins engine.

After transitioning to the Aisin AS69RC—a more robust version of the 68RFE—Ram decided in 2025 to retire Aisin transmissions and adopt the ZF PowerLine.

A Proven Design

To create this new transmission, the design is based on the legendary ZF 8HP, continuously refined since 2008. ZF reused its operating principles to develop a commercial version called PowerLine. This transmission is also widely used in various commercial applications and can handle loads of up to 57,000 lbs (approximately 26 tonnes).

Measuring just 29.7 inches in length (75.4 cm) and weighing only 328 lbs dry (148.7 kg), this transmission uses five clutches, two of which are open in each gear. It was designed to minimize the number of moving parts and integrate as many components as possible within the housing, reducing exposed elements.

It uses a torque converter equipped with a turbine featuring a torsional damper, which helps absorb vibrations from the diesel engine. This system can also lock up at very low RPM to improve power transfer, regardless of the gear. For 3500 to 5500 models, the transmission can also be equipped with a power take-off (PTO) system, allowing it to drive auxiliary systems such as hydraulic pumps or other work accessories. This system can handle up to 500 lb-ft of torque.

A Significant Leap Forward

The improvements brought by this transmission are substantial. First, being lighter, it increases the truck’s payload capacity while reducing fuel consumption by about 10% compared to the previous transmission. Acceleration times have also improved by 30%.

In terms of performance, gear shifts are quick and smooth—hard to fault and particularly responsive. The transmission can also skip gears to optimize efficiency. As for responsiveness, it reacts quickly to driver input, without hesitation.

The ZF 8-speed automatic transmission is likely one of the best in automotive history. Offering a commercial-grade version was a smart move, and it has been executed brilliantly. Now, it remains to be seen how it will perform in terms of long-term durability—but all indications suggest that the Cummins engine has finally found its perfect match in the Ram lineup.