2025 RAM Heavy Duty Road Test

RAM Heavy Duty trucks might not look very different on the outside for 2025, save for a refreshed grille, lights, and wheels, and that’s because the real changes are under the skin. While the gasoline drivetrain soldiers on unchanged with the tried and true 410 hp and 429 lb-ft of torque 6.4L Hemi, backed by an 8-speed automatic transmission, it’s the diesels that see all of the attention on this refresh.

RAM and Cummins have a new deal in place through the 2030 model year and RAM fans will find the 6.7L 24-valve Cummins turbo diesel that they are accustomed to, under the hood. However, this new 6.7L, which is available for a $12,595 upcharge, is upgraded in the areas of NVH and power delivery. The old standard and high-output engine designations are no more, and the two six-speed automatic transmissions have been replaced with an all-new 8-speed medium-duty ZF transmission, which should equate to a long service life and increased durability.

So, what’s different? Well, for starters, the intake is no longer integrated, instead Cummins opted for a bolt-on aluminum intake with longer runners, intake and exhaust valves that are 2mm larger, and 3,000 psi higher fuel pressure, which now comes in at 32,000 psi from a new Bosch CP8 fuel pump. Cummins did keep hydraulic lifters and the CGI block has been replaced with cast iron. Another big change includes swapping the problematic grid heater for glow plugs. A new turbocharger is designed to spool up faster and helical gears used in the cam drive and fuel pump drive keep things quieter. Other improvements include changing the location of the filters to the top of the engine for easier servicing.

While some customers might be disappointed that the power output is “only” 430hp and 1,075 lb-ft of torque, this is now the only output level offered. Depending on whether you were a high-output customer or a standard-output customer in the previous generation, the new engine is 10 horsepower more and the same torque as before or a whopping 60 horsepower and 225 lb-ft of torque healthier than the standard output model from 2024.

As previously mentioned, the new ZF automatic is based on the medium-duty Powerline 8-speed transmission, which RAM refers to as a TorqueFlite HD. This transmission is known for its robustness and durability, and with two more gears it gives the notoriously short-powerband Cummins some real-world flexibility. Because of a first gear (4.71) that is lower than the previous transmission options and an eighth gear (0.67) that is higher than the old 6-speed, all RAMs are now equipped with 3.42 gears, which allow for better off-the-line pulling with the new trans and lower RPM at highway speeds for better efficiency.

The RAM Heavy Duty cabin mimics that of its little brother, the RAM 1500, for 2025. However, thanks to customer feedback, the Heavy Duty eschews the half-ton’s nearly universally loathed dial shifter, replacing it with the universally missed and highly requested column shifter. The new column shifter, while looking the part, doesn’t actually have any mechanical connection to the electronic transmission. However, it was engineered to have the same feel as a traditional mechanical column shifter, including the detents and shift effort. We think it’s a really close approximation to the real thing.

Other tech includes Uconnect 5 and optional 12 or 14.5-inch screens in the vertical portrait arrangement. RAM's 10.25-inch passenger screen is also available, but it’s an option we haven’t found much use for. One option we do appreciate are the side-by side wireless charging pads that live at the front of the expansive center console.

RAM’s Heavy Duty is arguably the class-leader when it comes to interiors, mastering areas of ergonomics, visibility, and quality of materials, especially on high-end models. The RAM Heavy Duty is incredibly quiet, lacking any discernible wind noise at highway speeds. Even when driving through gusty winds or under load, conversations could be had at normal volumes. Those who choose the diesel model will be impressed with just how well NVH is controlled, with the signature Cummins rumble muted to the point of nearly missing.

From the moment you pull away from a stop, it’s clear that the real star of the show is the new ZF transmission. It feels incredibly well integrated, with no holes between your right foot and the output. Low gearing in First means the truck, whether it is empty or fully loaded, pulls away from the line smartly and puts down the power needed to merge confidently.

The Cummins engine has always had a short powerband, which at times could feel like you were running out of steam, especially when towing up a long grade with a heavy load. However, the new truck feels so much more flexible with its power delivery, pulling hard and able to grab a downshift when needed, thanks to those two extra gears. The new transmission is a huge win for the driving experience and driver confidence, and we loved the quick, nearly imperceptible shifts, which contrasts against the mule kicks of the old Aisin six-speed transmission on the previous HO model.

While heavy-duty trucks can often be a handful to drive, especially when loaded or with a trailer in tow, we found that the RAM is drama-free and unflappable. It was noteworthy that in windy conditions, that we felt comfortable enough in the RAM to pilot it with just one hand and that was with a mix of trucks and loads, ranging from a single rear wheel RAM 2500 with a car trailer weighing around 7,500 pounds on up to a RAM 3500 dually with a 19,000-pound, triple-axled, gooseneck, hauling a Case tractor. Thanks to adaptive cruise control and an integrated exhaust brake that worked in perfect harmony, we never had to think about controlling our downhill speed.

We sampled the diesel-powered 2500 Rebel, which is sort of a Power Wagon light, on the trail. The Rebel features Bilstein shocks, skid plates, off-road tires, and a rear locker. While it doesn’t have the Warn winch, a disconnecting front sway bar, or the front locker of the Power Wagon, at 2,450 pounds of payload and 19,890 pounds of towing capacity it does beat the gasser Power Wagon’s 1,570 pounds of payload and 10,530 pounds of towing capacity by a not insignificant margin.

The Rebel, with its 20-inch wheels, could be a little harsh when unladen on trail, it never failed to handle anything we threw at it. We think it could benefit from a big-body 60mm Bilstein for more control, but if you need off-road capability in a heavy-duty package, it’s not a bad choice.

Despite not looking all that different from the previous model, the changes under the hood are a significant upgrade. With strong power and a new transmission that really allows the Cummins to shine, RAM is as competitive as anything out there in terms of capability and is worth a look, especially if you are looking to upgrade from an older generation. Add to that one of the best interiors in the business and as much tech as you want, and the RAM Heavy Duty is a great option.