2025 Dodge Ram 6.7L Cummins

The release of the 2025 Ram 2500, 3500, 4500, and 5500 featuring the dependable 6.7L Cummins came with some big surprises under the hood. At first glance, you’ll probably immediately notice the changes to the grill, hood, headlights, and bumper as distinguishing differences from 2024 model years. This is fairly common practice with Ram over the years to deliver a distinct look while only modifying the front clip. So that still begs the question: what did Ram and especially Cummins change on the 6th Gen Rams and was it for the better?

Lets get the most important details out of the way first and foremost: the transmission. Ram has long been regarded as falling short of potential in the transmission department. The problem goes all the way back to the 518’s in the 1st Gens up to the 68RFE’s. Over the years, high failure rates plagued Cummins powered Rams when compared to the Allison backed Chevy’s or Ford’s E4OD through the ten speed Torqshift. So what changed? Germany based ZF built the TorqueFlite HD 8HP75 8 speed transmission that is now backing all Cummins powered Rams. Previous 6.7 models had either a 68RFE or two iterations of the Aisen depending on whether the truck was an HO model or pickup versus cab and chassis. The 8HP75, though, is not a completely new transmission, just a new version of it for this application. Featuring adaptive electronic control for smooth shifts no matter the conditions and automatic or Electronic Range Select (ERS) manual control deliver options to aid the driver whether towing a gooseneck trailer up a steep grade or in stop-and-go traffic in the blistering heat. The torque converter will lock with a turbine torsional damper for low lock up speeds even in 1st gear, all the way through 8th to get the power coming out of the engine to the ground. There is a five clutch pack design that only has two open clutches in any gear. The added gears will bring to the table reduced RPM drops between gears providing a better driving and towing experience coupled with improved overall power and fuel efficiency.

8HP75 Gear Ratios:

• 1st 4.71
• 2nd 3.14
• 3rd 2.10
• 4th 1.67
• 5th 1.29
• 6th 1.00
• 7th 0.84
• 8th 0.67
• Reverse 3.30

The transfer case is a Borgwarner BW 44-48 part time four wheel drive with electric shift featuring the typical two wheel drive, as well as high and low four wheel drive, and neutral. Low range mode will drop you down to an impressive 2.64 ratio for crawling your way through nasty terrain or aiding in backing up a trailer.

Now that we got the transmission news out of the way, lets jump into the next biggest set of changes, starting with….GLOW PLUGS! That’s right, Cummins engines have included a grid heater to warm incoming air in the cylinders since the first Ram rolled off the assembly line with a 12 Valve Cummins under the hood. They’d left the failure prone glow plugs to the Ford and Chevy guys, but no longer! Possibly the switch came from the failure prone grid heater nut that has caused some notorious issues in 6.7’s where literally a retaining nut for the grid heater falls into a cylinder and next thing you know, you’re getting a new engine.

The next change is that of the intake manifold and how cold air enters the engine. Historically, these trucks have featured an intake manifold that swoops up from the drivers side intercooler pipe, dropping down onto a bulge on the side of the head, called a plenum, which is centered towards the front cylinders, passes through the previously mentioned grid heater, and then enters the combustion chamber. There have been a handful of aftermarket companies that have released “side draft” manifolds in which you literally machine off this “bulge” from the head and bolt on a manifold that enters laterally into the side of the head. Pretty cool, but obviously a tad labor intensive. Well, with the change up to the grid heater, this feature now comes right from the factory. Underneath this head, Cummins finally realized that the CGI (Compacted Graphite Iron) block was a big mistake in their effort to shave a few pounds and reverted back to a gray iron block (thank goodness!). Back inside of the head, you’ll find pushrod operated overhead valves, 24 of them to be exact, and hydraulic lifters.

Engine Specifications:

• Displacement: 408 cu. in.
• Bore x Stroke: 4.21 x 4.88
• Compression Ratio: 16.2:1
• Horsepower: 430 hp @ 2,800 rpm
• Torque: 1,075 lb.-ft. @ 1,800 rpm
• Maximum High-Idle Engine Speed: 3,200 rpm
• Oil Capacity: 12.0 quarts with filter
• Coolant Capacity: 23.8 quarts

The 2025 model year finally saw Cummins get on board with top feed piezo injectors as opposed to the Common Rail style injectors that have been in use since 2003 model years. The top feed Both of these models are similar to one another in that they are electronically controlled and comprise the ability to operate at extremely high pressures (around 30,000 psi), but where the piezo injector shines in its ability to more accurately control the fuel’s activation (i.e. opening and closing) for better atomization of the fuel. This in turn creates improved combustion efficiency, which nets better power and fuel economy with lower exhaust gas temperatures. Its all science here folks!

Beyond the upgrade to injectors, a CP8 injection pump was introduced. Historically, 2003 was also the first year of a high pressure common rail injection pump, specifically the CP3. This same basic pump was used all the way until 2019 model years when they thought it was a good idea to implement the same failure prone CP4 that GM and Ford had been using with lackluster results. After a zillion failures (maybe not that many), Cummins at least wised up compared to their competition and 2021 model years reverted back to the tried and true CP3. That said, no one thought this would be a permanent fix, rather a band-aid until a better pump could be developed, and introducing the CP8. You may be asking yourself, what about the CP5, CP6, and CP7? Well, probably only Bosch will know the answer to that, but we’re looking forward to some reliability out of the CP8 pump.

With all of these powertrain revisions, did Ram opt to overhaul their suspension and steering? Since there weren’t any major flaws with the design that had essentially been released in the 2012 or 2013 model years (depending on whether the truck was a 2500 or a 3500), things were left relatively unchanged with the exception of an optional adaptive steering. Up front on four wheel drive models, we’ll find a 9.25” beam front axle with center disconnect being held in place by stout radius arms, coil springs, and track bar. Out back, however, you’ll have some options. For Ram 2500’s you can opt for rear coil spring or a full air ride where 3500’s adorn leaf springs or air bag assisted leaf springs. Hanging below these is your choice of an AAM 11.5 beam rear axle or an AAM 12.0 on 3500 Max Tow iterations. Inside of those axles, you’ll find that most models are equipped with a relatively tall 3.42 gears but with optional 3.73 or 4.10’s to aid in towing or those running larger than stock tires (or both).

Here at Diesel Power Products we have all the suspension parts you need to get your 2025 Cummins literally “up” and running. Choose between the best lift or levelling kits, control arms, steering stabilizers, sway bar links, shocks, and more from some of the most trusted manufacturers in the business.

Overall, Ram made some big headway in departments that desperately needed attention. How long have their transmissions been the brunt of every joke from Chevy and Ford drivers? Elimination of the notorious ticking time bomb known as the grid heater bolt and replacing with old school glow plugs. Top fed piezo injectors fed by a CP8, replacing common rail technology. Only time will tell if the updates are for the positive or not.

Disclaimer: Diesel Power Products is not affiliated with Cummins or any of its subsidiaries or related companies. Unless a product is specifically identified as a Genuine Cummins product that has not been remanufactured, modified, or refurbished, Cummins makes no representation or warranty about the product and has not authorized, tested, or approved the parts for use in genuine Cummins brand products.