2015 Ram 3500 6.4 Hemi Specs: Power, Towing, Payload
The 2015 Ram 3500 6.4L Hemi V8 makes 410 horsepower and 429 lb-ft of torque, the mid-tier gas option between the standard 5.7L Hemi and the 6.7L Cummins Turbo Diesel. Ram built this engine specifically for the 2500 and 3500 Heavy Duty lineup, adapting the block from the SRT performance line and retuning it for towing duty.
That single engine choice changes almost every number that matters on this truck. Towing capacity, payload, and GCWR all shift depending on whether you’re running a single rear wheel or dual rear wheel setup, and which axle ratio came on your build sheet.
This page breaks down the full 6.4L Hemi spec sheet, the exact towing and payload numbers by configuration, and the maintenance basics every owner should have on hand.
2015 Ram 3500 6.4L Hemi Specs
Power, towing and payload by configuration
6.4L Hemi V8
- 410 hp / 429 lb-ft
- Up to 16,030 lbs max trailer
- 87 octane regular unleaded
- Lower upfront and maintenance cost
6.7L Cummins Diesel
- 350 to 385 hp / 660 to 865 lb-ft
- 30,000 lbs best-in-class rating
- Ultra low sulfur diesel
- Better for frequent heavy towing
Full 2015 Ram 3500 6.4L Hemi Engine Specifications
Ram sourced the 6.4L Hemi’s architecture from the SRT performance engine, then retuned it for heavy-duty duty cycles. It uses the same deep-skirt cast-iron block construction as the 5.7L Hemi, but with larger bore and stroke dimensions and a lower 10.0:1 compression ratio built for regular unleaded fuel.
| Spec | 6.4L Hemi V8 |
|---|---|
| Displacement | 392 cu in (6,417 cc) |
| Bore x Stroke | 4.09 x 3.72 in |
| Compression Ratio | 10.0:1 |
| Valve System | Pushrod OHV, 16 valves, MDS cylinder deactivation with hydraulic roller lifters |
| Power (SAE gross) | 410 hp @ 5,600 rpm (370 hp @ 4,600 rpm in Mega Cab) |
| Torque (SAE gross) | 429 lb-ft @ 4,000 rpm |
| Max Engine Speed | 5,800 rpm, limited |
| Fuel Requirement | 87 octane regular unleaded |
| Oil Capacity | 7.0 qt (6.6 L) |
| Coolant Capacity | 15.75 L |
For context, the standard 5.7L Hemi in the same truck makes 383 hp and 400 lb-ft at the same RPM points, while the 6.7L Cummins ranges from 350 hp and 660 lb-ft up to 385 hp and 865 lb-ft depending on the transmission [source: media.fcanorthamerica.com official 2015 Ram 3500 spec sheet].
That power gets to the wheels through one specific transmission, and the axle ratio you choose changes every capacity number in the next section.
2 Axle Ratio Options for the 6.4L Hemi Transmission
Every 2015 Ram 3500 6.4L Hemi comes paired with the 66RFE six-speed automatic. There is no manual transmission option with this engine, that’s reserved for the Cummins.
| Gear | Ratio |
|---|---|
| 1st | 3.23 |
| 2nd | 1.84 |
| 3rd | 1.41 |
| 4th | 1.00 |
| 5th | 0.82 |
| 6th | 0.63 |
| Reverse | 4.44 |
Buyers could order the 6.4L Hemi with a 3.73 or a 4.10 rear axle ratio. The 4.10 gears trade a bit of highway fuel economy for a noticeably higher GCWR and max trailer rating, since the engine works less to turn the wheels under load.
That 3.73 versus 4.10 axle choice is the single biggest swing factor in the towing chart below.
2015 Ram 3500 6.4L Hemi Towing and Payload by SRW and DRW
These are the official SAE J2807 compliant numbers from Ram’s 2015 towing guide, broken out by cab configuration, rear wheel setup, and axle ratio [source: ramtrucks.com 2015 Ram 3500 towing chart].
| Configuration | Axle Ratio | GVWR | Payload | GCWR | Max Trailer |
|---|---|---|---|---|---|
| Reg Cab 4×4 SRW | 3.73 | 10,400 lbs | 4,450 lbs | 19,900 lbs | 12,780 lbs |
| Reg Cab 4×4 SRW | 4.10 | 10,400 lbs | 4,450 lbs | 22,900 lbs | 15,780 lbs |
| Reg Cab 4×4 DRW | 3.73 | 13,300 lbs | 7,100 lbs | 19,900 lbs | 12,530 lbs |
| Reg Cab 4×4 DRW | 4.10 | 13,700 lbs | 7,500 lbs | 23,400 lbs | 16,030 lbs |
| Crew Cab Long Box 4×4 SRW | 3.73 | 11,400 lbs | 4,940 lbs | 19,900 lbs | 12,280 lbs |
| Crew Cab Long Box 4×4 SRW | 4.10 | 11,400 lbs | 4,940 lbs | 22,900 lbs | 15,280 lbs |
| Crew Cab Long Box 4×4 DRW | 3.73 | 13,300 lbs | 6,560 lbs | 19,900 lbs | 11,990 lbs |
| Crew Cab Long Box 4×4 DRW | 4.10 | 14,000 lbs | 7,260 lbs | 23,400 lbs | 15,490 lbs |
The highest numbers on the 6.4L Hemi come from the Regular Cab dual rear wheel truck with 4.10 gears, at 16,030 lbs max trailer and 7,500 lbs payload. That’s the ceiling, not a number every 3500 6.4L Hemi carries.
GCWR covers the truck’s own weight, the trailer, passengers, and cargo combined. If you’re close to your max trailer figure, check your specific build’s door jamb sticker before you hook up.
For the full year-by-year breakdown across every Ram 3500 engine option, see our Ram towing capacity chart by year.
Whichever number applies to your truck, the 6.4L Hemi needs specific fluids to keep pulling that weight reliably.
Exact 6.4L Hemi Oil Type and Fluid Capacities
The 6.4L Hemi takes 7 quarts of 0W-40 full synthetic oil with a filter change, the factory spec confirmed by both AMSOIL’s fitment data and Ram’s official documentation. The coolant system holds 15.75 liters.
| Fluid | Type | Capacity |
|---|---|---|
| Engine Oil | 0W-40 full synthetic | 7.0 qt (6.6 L) |
| Coolant | 5-year/100,000-mile HOAT | 15.75 L |
| Transmission | ATF+4 | Verify against owner’s manual, service type dependent |
| Battery | Group 65, maintenance-free | 730 CCA |
The alternator is a 180-amp unit standard with the 6.4L Hemi, with a dual 220/160-amp option available for trucks running heavy electrical accessories.
Some owners on BobIsTheOilGuy have run 5W-30 without issue, but 0W-40 is what Ram specs from the factory, and it’s the safer call for a truck doing regular towing [source: BobIsTheOilGuy 2015 6.4 Hemi oil spec thread].
For a full breakdown of how the cooling system routes through the block and radiator, see our 6.4 Hemi cooling system diagram.
Fluids keep the engine running, but most shoppers still want to know how it stacks up against the diesel option.
Is the 6.4L Hemi Enough or Should You Step Up to the 6.7L Cummins
The 6.4L Hemi is not underpowered, but the torque gap against the 6.7L Cummins is real once you’re loading a heavy trailer.
| Metric | 6.4L Hemi | 6.7L Cummins |
|---|---|---|
| Horsepower | 410 hp | 350 to 385 hp |
| Torque | 429 lb-ft | 660 to 865 lb-ft |
| Max Trailer (best config) | 16,030 lbs | 30,000 lbs class-leading |
| Real-World MPG | Roughly 10 to 13 city, 15 to 17 highway | Roughly 2 to 5 mpg better than the Hemi |
The Cummins pulls ahead on every towing number, and that’s before counting its 30,000-lb best-in-class diesel towing rating that Ram advertised for the 2015 Heavy Duty lineup [source: 2015 Ram 2500/3500 official brochure].
We recommend the 6.4L Hemi for owners who tow occasionally and want lower upfront and maintenance costs. If you’re regularly pulling a heavy 5th wheel or gooseneck, the Cummins justifies its price premium.
For the same engine in the shorter-wheelbase 2500, see our Ram 2500 6.4 Hemi specs breakdown.
Whichever engine you’re running, here’s what to expect day to day.
2015 6.4L Hemi Real World MPG and Common Problems
Ram never published an EPA rating for the 6.4L Hemi in this weight class, so real-world numbers come from owner logs. Forum-reported averages run roughly 10 to 13 mpg city and 15 to 17 mpg highway unloaded, dropping to 8 to 11 mpg while towing [source: BobIsTheOilGuy and RamForumZ owner threads].
Early-production 2015 trucks had a documented issue with EGR temperature sensor codes, specifically P04D0, P04CE, P2457, and P040B, sometimes triggering the check engine light repeatedly even after sensor replacement [source: RamForum.com owner thread].
Consumer Reports rates the 2015 Ram 3500 below average for overall reliability, with the exhaust system flagged as the most commonly reported trouble spot across the model year, not an issue isolated to the 6.4L Hemi specifically [source: Consumer Reports 2015 Ram 3500 reliability].
None of this changes the maintenance basics every 6.4L Hemi owner should have on hand.
If you’re chasing a check engine light or rough idle on your own truck, our 6.4 Hemi problems guide covers the most common codes and fixes.
Getting the Most Out of Your 2015 Ram 3500 6.4L Hemi
The 2015 Ram 3500 6.4L Hemi delivers 410 hp and 429 lb-ft, with towing and payload numbers that swing from roughly 12,000 lbs to over 16,000 lbs of max trailer depending on your SRW or DRW configuration and axle ratio.
The engine alone doesn’t tell the whole story. Your specific build’s GVWR, GCWR, and payload rating live on your door jamb sticker, and that’s the number to trust over any generalized spec sheet.
Run 0W-40 synthetic oil on schedule, and this engine has a well-earned reputation for lasting well past 200,000 miles with normal maintenance.
Frequently Asked Questions
What is the horsepower of the 2015 Ram 3500 6.4 Hemi?
The 2015 Ram 3500 6.4L Hemi makes 410 horsepower at 5,600 rpm in most configurations. Mega Cab models are rated slightly lower at 370 hp due to different exhaust routing. Torque output is 429 lb-ft at 4,000 rpm across all cab styles.
How much can a 2015 Ram 3500 6.4 Hemi tow?
Max trailer rating ranges from 11,990 lbs to 16,030 lbs depending on SRW versus DRW and axle ratio. The highest figure applies to a Regular Cab dual rear wheel truck with 4.10 gears. Check your door jamb sticker for your exact truck’s rating.
What oil does the 6.4 Hemi in a Ram 3500 take?
The 6.4L Hemi takes 7 quarts of 0W-40 full synthetic oil with a filter change. This is the factory spec confirmed by Ram’s official documentation. Some owners run 5W-30 without issue, but 0W-40 is the recommended viscosity for towing use.
Is the 6.4 Hemi or 6.7 Cummins better for towing?
The 6.7L Cummins tows significantly more, with a best-in-class 30,000-lb rating on the 2015 lineup versus the Hemi’s 16,030-lb ceiling. The Hemi costs less upfront and to maintain, making it better suited to occasional or lighter towing. Frequent heavy towing favors the Cummins.
What is the payload capacity of a 2015 Ram 3500 with the 6.4 Hemi?
Payload ranges from 4,450 lbs on a single rear wheel truck up to 7,500 lbs on a dual rear wheel Regular Cab with 4.10 axle gears. Crew Cab configurations run slightly lower than Regular Cab due to added body weight. Your exact figure depends on trim level and installed options.
