Recent Post
Why Your Truck Keeps Burning Up Alternators
Alternator Output at Idle: The Number Nobody Publishes
How to Choose a High Output Alternator for a Diesel Truck
The Complete Dual Alternator Conversion Guide
Duramax Dual Alternator Bracket Kits: Which One Fits Your Truck
What Belt Do You Need for a High Output Alternator?
RAM 6.7 Cummins Dual Alternator Fitment: What Actually Fits Your Year
RAM 2500 and 3500 6.7L Cummins™ trucks are covered from 2011 through 2024 across three output tiers — 240 amp at $429, 320 amp at $519, and 370 amp at $599 — with a belt-included kit and a billet version of the 370 also available. If you want a second alternator rather than a larger single one, dual-alternator bracket kits cover 2013–2018 and 2020–2024, and the 2020–2024 kit ships with a 370 amp alternator in the box.
The one thing to understand before you order anything: these trucks use computer-controlled charging, and that changes what an upgrade actually gets you. More on that below, because it's the single most common source of disappointment on this platform.
Which alternator fits a RAM 6.7 Cummins?
Coverage runs 2011–2024 on both the 2500 and 3500 pickup. Dodge-badged 2007–2010 trucks share the same alternator family.
| Output | Part number | Price | Notes |
|---|---|---|---|
| 240 A | 11378240 |
$429 | Entry tier. Meaningful gain over factory for lighting, aux circuits, moderate accessory loads |
| 320 A | 11378320 |
$519 | The volume choice for plow, spreader and inverter trucks |
| 370 A | 11378370 |
$599 | Highest single-unit output on the platform |
| 370 A + belt | 11378370-WB |
$599 | Same unit, belt included — the simpler order |
| 370 A billet | B11378370B |
$699 | Billet case |
All are built for the factory computer-controlled charging strategy.
Which tier? Total what actually runs continuously while the truck is working, then add roughly 50% for thermal headroom. A truck with a plow, spreader, beacons and full lighting will typically land on the 320. A service truck running a 2,000-watt inverter usually needs more than any single alternator provides, which is where the dual kits come in. The full method is in What size alternator does your work truck need? →
Why does computer-controlled charging matter on this platform?
On these trucks the ECU commands charging voltage and varies it deliberately, based on battery state of charge, temperature and load. It is not a fault.
A high output alternator increases available amperage. It does not raise your charging voltage. Voltage still follows the factory strategy, because the factory strategy is still in control. If you want a fixed higher voltage, that is an ECU tuning question, not an alternator question.
This matters because it sets the right expectation. If your complaint is "my voltage reads 13.4 instead of 14.2," a bigger alternator will not change that number. If your complaint is "voltage sags when the plow lifts and the lights dim in the lot," that is an amperage problem and a bigger alternator is exactly the fix.
Which dual alternator bracket kit fits your truck?
Two year ranges are covered.
| Years | Part number | Price | What's included |
|---|---|---|---|
| 2013–2018 | CTDDB-1318 |
$399 | Bracket only — no belt, no alternator |
| 2013–2018 | CTDDB-1318CA |
$799 | Cast kit with a 370 A alternator |
| 2013–2018 | CTDDB-1318BA |
$899 | Billet kit with a 370 A alternator |
| 2020–2024 | CTDDB-2024CA |
$699 | OE-style cast kit with a 370 A 11378370 included |
A billet version of the 2020–2024 kit is also available; confirm the current part number and price when you order.
Two things people get caught by. The CTDDB-1318 at $399 is a bracket on its own — you supply the alternator and the belt, and a dual setup needs a different belt length than the truck came with. That is a required second purchase, not an upsell. And check the 2019 model year specifically before ordering: it sits between the two published ranges, so confirm fitment rather than assuming either kit covers it.
Do you need a second alternator, or a bigger single one?
Most people asking this need the bigger single unit.
A larger single alternator is the right answer when your continuous load sits under roughly 320 amps with headroom, you want the simplest install, and you would rather not add a second belt path to maintain. For the large majority of plow trucks, service trucks and towing rigs, the 320 or 370 covers it.
A dual setup earns its cost when your continuous load plus headroom exceeds what one alternator can deliver — typically a 2,000-watt-plus inverter, a welding rig, a heavily upfit service body, or a truck that genuinely cannot be down and needs redundancy.
The deeper version of that decision, including belt path and charge wiring: The complete dual alternator conversion guide →
What about a 5.9L Cummins?
Different platform, and a genuinely good option on it. The B13302370B is a 370 amp Billet Elite large-case unit covering 1988–2002, at $629.
Two things make it unusually easy to fit. It produces roughly 200 amps at idle, which is one of only a handful of published idle figures anywhere in this market and the number that actually decides whether a work truck stays charged. And it mounts to the factory bracket with a near-stock pulley, so no belt change is required — a large capacity increase with no accessory drive modification.
An external regulator setup is available for it, using the P102 harness at $39. Note this is a charging control accessory rather than a connector adapter.
Why idle output matters more than the rating on the box: Alternator output at idle →
What else you'll need
-
Belt. The
-WBalternator kits include one. TheCTDDB-1318bracket does not, and a dual conversion changes the required length. What belt do you need? → - Charge cable. Factory cable is sized for the factory alternator. Roughly doubling output through undersized cable produces voltage drop and heat. 1/0 gauge on the charge wire and ground is the usual answer above 250 amps.
- Grounds. Engine-to-frame and frame-to-body straps corrode, and a bad ground presents exactly like a weak alternator.
- Pulleys. The pulley line is 17 mm bore and fits these alternators specifically — not factory replacements.
Frequently asked questions
What high output alternator fits a 2019 or newer RAM 6.7 Cummins?
RAM 2500 and 3500 6.7L Cummins coverage runs from 2011 through 2024, so 2019 and newer trucks are included. Three output tiers are available: 240 amp at $429, 320 amp at $519, and 370 amp at $599, plus a belt-included version of the 370 and a billet version at $699. All are built to work with the factory computer-controlled charging strategy, so amperage increases while voltage continues to follow the factory control.
Is there a dual alternator bracket for a 2020 to 2024 RAM 6.7?
Yes. The CTDDB-2024CA is an OE-style cast dual alternator bracket kit for 2020 through 2024 RAM 6.7L Cummins at $699, and it ships with a 370 amp alternator included rather than requiring you to source one separately. A billet version is also available. For older trucks the 2013 through 2018 range is covered by three separate part numbers at different levels of completeness.
What is the difference between the CTDDB-1318 and the CTDDB-1318CA?
The CTDDB-1318 at $399 is the bracket on its own, with no alternator and no belt included. The CTDDB-1318CA at $799 is a complete cast kit that includes a 370 amp alternator, and the CTDDB-1318BA at $899 is the billet equivalent. If you buy the bracket alone, remember that a dual alternator setup requires a different belt length than the truck came with, so budget for that as a required part rather than an accessory.
Will a high output alternator raise my charging voltage?
No, and this is the most common misunderstanding on this platform. RAM 6.7 Cummins trucks use computer-controlled charging, where the ECU commands and varies voltage based on battery state of charge, temperature and load. A high output alternator increases the amperage available, but voltage still follows the factory strategy. A fixed higher voltage requires ECU tuning rather than a different alternator.
Do I need a dual alternator setup or just a bigger single one?
Most people need the bigger single unit. A 320 or 370 amp alternator covers the large majority of plow trucks, service trucks and towing rigs, and it is a simpler install with one less belt path to maintain. A dual setup earns its cost when continuous load plus headroom exceeds what a single alternator can deliver, which in practice usually means a 2,000-watt-plus inverter, a welding rig, a heavily upfit service body, or a truck that needs redundancy because it cannot be down.
What alternator fits a 5.9L Cummins?
The B13302370B is a 370 amp Billet Elite large-case unit covering 1988 through 2002 at $629. It produces roughly 200 amps at idle, which is one of very few published idle figures in this market, and it mounts to the factory bracket with a near-stock pulley so no belt change is required. That combination makes it an unusually straightforward upgrade for a large capacity increase. An external regulator option is available using the P102 harness at $39.
Do I need to upgrade my charge cable too?
Almost certainly, above about 250 amps. Factory charge cable is sized for the factory alternator, and pushing significantly more current through undersized cable creates voltage drop and heat rather than delivering the capacity you paid for. One-zero gauge on both the charge wire and the ground is the common answer. While you are there, check the engine-to-frame and frame-to-body ground straps, because a corroded ground presents exactly like a weak alternator and costs nothing to fix.
Does a belt come with the alternator?
It depends on the part number. Alternator kits flagged with a -WB suffix include a belt, such as the 11378370-WB. Standalone alternators do not. The CTDDB-1318 bracket does not include a belt either, and because a dual alternator conversion changes the required belt length, that is a part you will need regardless of what came in the box. Confirm belt inclusion before ordering rather than after.
Power Stroke™, Cummins™, Duramax™, RAM™, Ford™, GM™ and Chevrolet™ are trademarks of their respective owners. Mechman® is not affiliated with, endorsed by, or sponsored by any vehicle manufacturer. Products are listed as compatible with the applications shown.