2018 Ram 3500 6.7 Cummins Specs By Transmission Guide 2026
2018 Ram 3500 6.7 Cummins specs depend heavily on transmission, axle ratio, cab, drivetrain, and SRW or DRW configuration. The same model year can mean a lower-output G56 manual truck, a 68RFE automatic truck, or a high-output Aisin dually.
The 6.7L Cummins Turbo Diesel is the engine buyers usually want in a 2018 Ram 3500, but the badge alone does not tell you the truck’s real tow rating. You need to match the engine calibration, transmission, GVWR, GCWR, payload, and axle ratio before trusting any online max number.
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6.7L Cummins Output Changes By Transmission
The 2018 Ram 3500 Cummins does not have one single power rating. The G56, 68RFE, and Aisin AS69RC setups each use a different factory output level.
G56 6 Speed Manual
68RFE 6 Speed Automatic
AS69RC Aisin Automatic
Highest Official Trailer Rating
- Up to 31,210 lb with the right 2018 Ram 3500 configuration.
- Applies to a Regular Cab 4×2 DRW High Output Aisin truck with 4.10 axle ratio.
- GVWR, GCWR, axle ratio, cab, drivetrain, and SRW or DRW setup all change the final rating.
Core Maintenance Specs
- Engine oil with filter is 12 quarts.
- Cooling system capacity is 5.7 gallons.
- DEF tank capacity is 5.5 gallons for 2500 and 3500 pickups.
Key 2018 Ram 3500 Cummins Engine Specs
The 2018 Ram 3500 used the 6.7L Cummins Turbo Diesel inline-six as its main diesel engine. Cummins lists the 2018 6.7L Turbo Diesel as available in Ram 2500 and Ram 3500 pickups, with output up to 385 horsepower and 930 lb-ft of torque.
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For the Cummins platform layout, sensor locations, and component orientation, the 6.7 Cummins engine component layout is the best internal reference before you compare specs.
| Spec | 2018 Ram 3500 6.7 Cummins Detail |
|---|---|
| Engine | 6.7L Cummins Turbo Diesel I6 |
| Block And Head | Cast iron block and cast iron head |
| Compression Ratio | 16.2 to 1 |
| Fuel Type | Ultra-low sulfur diesel |
| Biodiesel Compatibility | Up to B20 where approved |
| Emissions System | SCR with DEF injection |
| Max Output | 385 hp and 930 lb-ft |
| Oil Change Interval | Up to 15,000 miles or 6 months for pickup models |
SCR means Selective Catalytic Reduction. DEF means Diesel Exhaust Fluid. The system injects DEF into the exhaust stream to help reduce NOx emissions.
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Cummins also notes that the MY 2013.5 and newer 6.7L Turbo Diesel is B20 capable where available. Ram’s diesel supplement still requires proper diesel fuel quality, correct DEF fluid, and the correct oil specification.
The engine is only part of the spec sheet. The next major divider is the transmission.
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How 3 Transmissions Change Cummins Output
The 2018 Ram 3500 6.7L Cummins Turbo Diesel had three major output profiles. The transmission determines which power rating the truck gets.
| Transmission | Cummins Version | Horsepower | Torque | Best Fit |
|---|---|---|---|---|
| G56 6 Speed Manual | Standard Output | 350 hp at 2,800 rpm | 660 lb-ft at 1,500 rpm | Manual buyers and lighter HD use |
| 68RFE 6 Speed Automatic | Standard Output | 370 hp at 2,800 rpm | 800 lb-ft at 1,600 rpm | Daily driving and general towing |
| AS69RC Aisin 6 Speed Automatic | High Output | 385 hp at 2,800 rpm | 930 lb-ft at 1,700 rpm | Heavy fifth-wheel and gooseneck towing |
The G56 manual is the lowest-rated Cummins setup. It appeals to manual diesel buyers, but it gives up a lot of torque compared with the automatic trucks.
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The 68RFE automatic is the middle setup. It is common in many Ram HD pickups and gives the standard-output Cummins a stronger 800 lb-ft torque rating.
The AS69RC Aisin is the high-output combination for Ram 3500 buyers. If you are shopping for maximum towing, this is the transmission to look for with the HO Cummins, DRW axle, and correct axle ratio.
More torque helps under load, but the final towing number still depends on the truck’s weight ratings.
What 2018 Ram 3500 Cummins Towing Specs Mean
The 2018 Ram 3500 Cummins towing rating is not one number. Ram’s official towing chart calculates trailer ratings by configuration and follows SAE J2807.
The highest trailer rating listed in Ram’s 2018 chart is 31,210 lb. That applies to a Regular Cab 4×2 DRW truck with the 6.7L Cummins High Output, AS69RC Aisin automatic, 4.10 axle ratio, 14,000 lb GVWR, and 39,100 lb GCWR.
| Example Configuration | Axle | GVWR | Payload | GCWR | Max Trailer Rating |
|---|---|---|---|---|---|
| Regular Cab 4×2 DRW HO Aisin | 4.10 | 14,000 lb | 6,580 lb | 39,100 lb | 31,210 lb |
| Regular Cab 4×4 DRW HO Aisin | 4.10 | 14,000 lb | 4,658 lb | 39,100 lb | 30,830 lb |
| Crew Cab 4×4 DRW HO Aisin | 4.10 | 14,000 lb | 5,470 lb | 39,100 lb | 30,100 lb |
| Regular Cab 4×4 SRW G56 Manual | 3.42 | 11,500 lb | 4,170 lb | 24,300 lb | 16,500 lb |
For the full configuration spread, use the 2018 Ram 3500 towing capacity chart alongside the VIN, axle ratio, door sticker, and hitch type.
The gap between 16,500 lb and 31,210 lb is why generic max towing numbers are risky. A manual SRW truck and a high-output Aisin dually are not the same towing platform.
Why Payload Limits Matter More Than Trailer Rating
Payload is often the hidden limit on a 2018 Ram 3500 Cummins. Ram defines payload as GVWR minus base weight, and the official towing chart says payload and trailer weight rating are mutually exclusive.
GVWR means Gross Vehicle Weight Rating. GCWR means Gross Combined Weight Rating. GAWR means Gross Axle Weight Rating.
A fifth-wheel or gooseneck trailer adds pin weight directly to the truck. Ram’s chart uses 15 percent tongue weight for a fifth-wheel or gooseneck and 10 percent for a conventional trailer.
That means passengers, hitch hardware, fuel, bed tools, cargo, and trailer pin weight all count against available payload. The Ram payload capacity chart is useful when you want to compare how Ram ratings change across HD trucks.
A 31,000 lb trailer rating does not mean every 2018 Ram 3500 Cummins can carry the real loaded pin weight from that trailer. The door sticker is the final check for the truck you are actually buying.
2018 Ram 3500 6.7 Cummins Oil And Fluid Specs
The 2018 Ram diesel supplement lists the 6.7L Turbo Diesel engine oil capacity with filter at 12 quarts, or 11.4 liters. The same supplement lists the 6.7L cooling system at 5.7 gallons, or 21.4 liters.
| Fluid Or Capacity | 2018 Ram 3500 6.7 Cummins Spec |
|---|---|
| Engine Oil With Filter | 12 quarts or 11.4 liters |
| Cooling System | 5.7 gallons or 21.4 liters |
| DEF Tank For 2500 And 3500 Pickups | 5.5 gallons or 21 liters |
| Standard Cab Long Bed Fuel Tank | 28 gallons |
| Crew Or Mega Cab Short Bed Fuel Tank | 31 gallons |
| Crew Cab Long Bed Fuel Tank | 32 gallons |
For engine oil viscosity, Ram recommends 15W-40 above 0°F, using oil that meets FCA Material Standard MS-10902 and API CJ-4. Below 0°F, Ram recommends 5W-40 synthetic oil that meets the same material standard and API category.
Ram’s supplement also states that pickup oil change intervals should not exceed 15,000 miles, 6 months, or 500 hours. Severe use, idle time, biodiesel use, and oil change indicator messages can shorten that interval.
For maintenance planning, the CCV filter is another Cummins service item worth checking. If crankcase ventilation is part of your service plan, see the related 6.7 Cummins CCV filter guide.
Which 2018 Ram 3500 Cummins Setup Is Best
If you tow heavy fifth-wheel or gooseneck trailers, look for the High Output 6.7L Cummins with the AS69RC Aisin automatic. The strongest factory numbers come from DRW trucks with the correct axle ratio, especially 4.10 gearing.
If you tow moderate loads and daily drive the truck, the 68RFE automatic can make more sense. It gives 370 hp and 800 lb-ft without requiring the high-output Aisin configuration.
If you want a manual diesel, the G56 is the only path. But the tradeoff is clear: 350 hp and 660 lb-ft is far below the Aisin high-output rating.
If you plan to modify the truck later, start with the right configuration instead of trying to make the wrong truck do the job. The best 6.7 Cummins upgrade paths should come after you confirm the truck’s baseline tow rating, drivetrain, and transmission.
For any used 2018 Ram 3500, verify these items before purchase:
- VIN-specific equipment
- Door sticker payload
- Axle ratio
- SRW or DRW rear axle
- Transmission type
- Hitch rating
- Trailer pin or tongue weight
The best 2018 Ram 3500 Cummins is not always the highest-output truck. It is the truck that matches your trailer, payload, drivetrain, and maintenance budget.
Key Takeaway For 2018 Ram 3500 Cummins Specs
The 2018 Ram 3500 6.7 Cummins specs split into three main power levels: 350 hp and 660 lb-ft with the G56 manual, 370 hp and 800 lb-ft with the 68RFE automatic, and 385 hp and 930 lb-ft with the AS69RC Aisin automatic.
For maximum towing, the high-output Aisin dually is the truck to look for. But towing safety still depends on GVWR, GCWR, payload, GAWR, axle ratio, hitch rating, and the door sticker.
Before buying or towing, match the published chart to the exact truck. That is the only way to turn the 2018 Ram 3500 6.7 Cummins specs into a safe real-world towing decision.
FAQ About 2018 Ram 3500 Cummins Specs
What Is The Horsepower Of A 2018 Ram 3500 6.7 Cummins
The 2018 Ram 3500 6.7L Cummins Turbo Diesel makes 350 hp with the G56 manual, 370 hp with the 68RFE automatic, and 385 hp with the AS69RC Aisin automatic. The Aisin version is the high-output setup.
How Much Torque Does A 2018 Ram 3500 Cummins Have
The 2018 Ram 3500 Cummins makes 660 lb-ft with the G56 manual, 800 lb-ft with the 68RFE automatic, and 930 lb-ft with the AS69RC Aisin automatic. Torque rating changes with transmission and engine calibration.
What Transmission Came With The 2018 Ram 3500 Cummins
The 2018 Ram 3500 Cummins was available with the G56 6 speed manual, 68RFE 6 speed automatic, and AS69RC Aisin 6 speed automatic. The Aisin automatic is tied to the High Output Cummins rating.
How Much Can A 2018 Ram 3500 6.7 Cummins Tow
The highest official 2018 Ram 3500 Cummins trailer rating is 31,210 lb. That rating applies to a specific Regular Cab 4×2 DRW HO Aisin truck with 4.10 gears, 14,000 lb GVWR, and 39,100 lb GCWR.
How Much Oil Does A 2018 Ram 3500 6.7 Cummins Take
The 2018 Ram 3500 6.7L Cummins Turbo Diesel takes 12 quarts of engine oil with filter. Ram recommends 15W-40 above 0°F and 5W-40 synthetic below 0°F, using oil that meets the required FCA and API specifications.
Is The Aisin Better Than The 68RFE For Towing
The Aisin AS69RC is the better factory choice for heavy towing because it pairs with the High Output Cummins rating of 385 hp and 930 lb-ft. The 68RFE is better suited to standard-output trucks, daily driving, and lighter towing needs.
