We know what the 2025 RAM 2500 and 3500 Heavy Duty pickups are going to look like, and we now have even more information about what might be coming under the skin. Basically, everything we’ve heard seems to be plausible. This news comes to us thanks to Lightning and Holman over at the Truck Show Podcast who interviewed an anonymous source, “Mr. X,” who seemingly has exclusive insider knowledge of the new Cummins diesel engine.

2025 Ram Heavy Duty and Chassis Cab front

Before we get into the specifics, we need state that this information is still considered a rumor. We have not been able to independently verify any of the information stated below, and RAM has not offered any official statements as of this time. But it’s sure fun to ponder.

The big news right out of the gate is that the rumors of a larger-displacement Cummins engine remain false, at least for the time being. Heading into 2025, the RAM Heavy Duty pickup will retain a 6.7-liter inline six-cylinder Cummins diesel engine. There will, however, be a host of significant changes, beginning with the block material. In 2019 Cummins swapped to a compacted graphite iron (CGI) block and for 2025 will revert to a gray iron block. This has several advantages, with one of the main being a potential improvement in noise, vibration, and harmonics.

2025 Ram Rebel Heavy Duty front three quarter

One of the most visible features of the new engine is said to be an all-new cylinder head. Most importantly, this new head is said to eliminate the much-belabored grid heater and instead makes the change to glow plugs. This will not only aid in improving cold starts and emissions, but will also protect the engine from the far too common grid heater bolt failure. This new head will also offer external fuel injectors and injector feed lines, which will make servicing the engine far easier by negating the need to remove the valve cover to work on fuel injectors.

2025 Ram Rebel Heavy Duty rear three quarter

A new Holset turbocharger will be employed as well. Power output is said to be 430 hp with 1,075 lb-ft of torque. Allegedly there will only be a single power output for 2025, instead of both the normal and high-output variants of 2024. This will offer a modest increase of 10 hp over the previous high-output, but a respectable 60 hp and 225 lb-ft bump over the standard engine. Practically speaking, this means the RAM 2500 will receive equivalent high-output power for the first time. This is a big deal.

If that’s not all impressive enough, the real party piece is what’s backing the improved Cummins engine. RAM is said to be finally putting its sometimes troublesome six-speed transmissions out to pasture and will instead be fitting its heavy-duty pickups with a new ZF-sourced 8-speed automatic. This new transmission, ZF’s 8AT Powerline, has been around for a long time serving in medium duty trucks and busses; it’s well-established in the space. This change should offer not only a boost in reliability, but also in acceleration and fuel economy.

Of course, all of this is just rumor until confirmed by RAM. But hey, we can all wish, right?