RAM has in no way officially debuted its 2025 RAM Heavy Duty truck, meaning we can only speculate about its capabilities, features, and technology. But because RAM needed to do some in-the-wild, real-world cooling testing without camouflage (implying there’s something to test) and knew the proverbial cat would be out of the bag, the manufacturer “wanted to share some quality exterior images with you rather than a badly lit snapshot out the window at 70 mph,” so we do know what it looks like. RAM said the official reveal “will take place at a later date.” It’s a month later, and we’re still patiently waiting. In the meantime, several juicy powertrain rumors have surfaced to keep us occupied until we know better.

2025 RAM Heavy Duty and Chassis Cab front

Exterior: Did You Notice That Grille?

Before we get to the powertrain rumors, let’s circle back to what we do know. The new RAM Heavy Duty is all-grilled-out, and we know this because of the official teaser images. The Rebel seems the grille-iest of the trims we’ve seen, leaving the internet up in arms as to what in the world RAM was thinking. The internet is generally negative, but you can’t deny the Rebel’s grille has lines that flow vertically, horizontally, and every which way—like a cheese grater that would dice the heck out of some cheddar. Basically, if you’re into big grilles, the new RAM is for you. If you can get past the grille, the rest of the truck pretty much looks the same—no surprises.

2025 RAM Rebel Heavy Duty rear three quarter

Engine: Will Single Cummins Surpass H/O?

The 2025 RAM Heavy Duty will still wear Cummins badges; there was no rumor that the Cummins would be going anywhere. Right now there are two versions of the Cummins: the standard-output (S/O) that makes 370 hp and 850 lb-ft of torque and the high-output (H/O) with 420 hp and 1,075 lb-ft. Although the S/O has been enough for RAM for years, it’s always been a bit of a bummer that you can’t option the H/O in the 2500. That might all change. There is rumor that we could see consolidation to one engine option that has a higher output than the current H/O.

According to Mopar Insiders and relayed by TFLtruck, “Several sources within the company have confirmed with us that those rumors are, in fact, true. RAM plans to simplify its Heavy Duty truck offerings with a single Cummins diesel option, which will be made possible by the upcoming ZF Powerline 8-speed automatic transmission. Expectations are high that this engine will surpass the performance metrics of the current H/O variant, promising more power and torque. This also means you won’t have to step up to a 3500 to get the most potent version of the Cummins.”

2025 RAM Rebel Heavy Duty front three quarter

Transmission: Will Cummins Get ZF 8-Speed?

That brings us to the next talking point—the transmission. The current Cummins is backed by a 6-speed 68RFE (S/O) or 6-speed Aisin (H/O). As we just saw, rumor has it that the upcoming single Cummins will be backed by a ZF 8-speed PowerLine automatic transmission, probably some sort of beefed-up variant of what backs the RAM Heavy Duty 6.4-liter Hemi V-8. This transmission should help improve fuel efficiency. Running an 8-speed tranny puts RAM closer to the 10-speed transmissions of GM and Ford, although ZF thinks 8 gears is perfect for truck applications. There’s also potential to tap into the transmission’s two PTOs (power take-offs) for hybridization, including mild hybrid and plug-in hybrid variants.

ZF has a facility building this transmission in Gray Court, South Carolina. According to ZF, “As part of a $200 million investment announced in 2021, ZF is now ramping up production to 200,000 transmissions per year by 2025 to satisfy demand from US commercial vehicle manufacturers, including three US-based customers.” The first PowerLine 8-speed rolled off this production line in late 2023.

Stay tuned for more on the 2025 RAM Heavy Duty truck.