Duramax Dual Alternator Bracket Kits | 400A | 2001–2022 | Mechman®
GM 6.6L Duramax · Dual Alternator
Add a 400-Amp Second Alternator to Your 6.6L Duramax
The 6.6L Duramax does the heavy lifting in work trucks, tow rigs, and diesel builds — and the more you add electrically, the harder a single alternator has to work. Mechman's year-specific dual-alternator kits bolt a 400-amp second alternator onto your Duramax to carry the load.
Why a Duramax needs a second alternator
Duramax trucks rarely live a stock life. Add a winch, a plow, a slide-in camper, an inverter and auxiliary batteries, work lighting, or a serious stereo, and total electrical demand quickly climbs past what one alternator was sized to deliver — especially at the low engine speeds where a diesel spends much of its time.
When demand outruns supply, voltage sags and the batteries discharge to cover the gap. The dependable fix is a second alternator dedicated to the extra load.
One bolt-on kit, one big block of headroom
Each kit adds a high-output 400-amp B11348400 alternator alongside the factory unit — a complete, bolt-on dual setup engineered for strength and durability. Everything needed for a clean install is supplied, and the factory alternator stays in place to run the truck's original systems.
Find your exact year — and check for a vacuum pump
Duramax brackets are year-specific, so match the kit to your truck. One detail trips people up: 2002–2005 trucks came either with or without a vacuum pump, and that changes the bracket. Pick the “with” or “without vacuum pump” kit to match your engine.
What's in a Duramax kit
- Dual-alternator bracket assembly
- B11348400 400-amp alternator (cast or anodized finish)
- Drive belt
- Wiring / harness
- Mounting hardware
Output Added
400A
Alternator
B11348400
Setup
Dual
Years
2001–2022
Shop by year
Pick your model year to land on the exact kit and part numbers for your truck (cast from $699, anodized $799).
GM 6.6L Duramax
2001
Dual kit · from $699
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GM 6.6L Duramax
2002–2005 — w/o Vacuum Pump
Dual kit · from $699
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GM 6.6L Duramax
2002–2005 — w/ Vacuum Pump
Dual kit · from $799
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GM 6.6L Duramax
2006
Dual kit · from $699
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GM 6.6L Duramax
2007–2009
Dual kit · from $699
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GM 6.6L Duramax
2010–2016
Dual kit · from $799
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GM 6.6L Duramax
2017–2019
Dual kit · from $699
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GM 6.6L Duramax
2020–2022
Dual kit · from $799
Shop →Frequently asked questions
Which Duramax kit do I need for my year?
Match the kit to your model year using the year-range options above. The brackets are application-specific from 2001 through 2022, so selecting your exact year ensures the correct bracket, belt, and fitment.
What's the 2002–2005 “vacuum pump” difference?
Some 2002–2005 Duramax engines have a vacuum pump and some don't, and that changes which bracket fits. Choose the “with vacuum pump” or “without vacuum pump” kit to match your engine — if you're unsure, check the front of the engine or ask our team.
Does it keep my factory alternator?
Yes. This is a true dual-alternator setup. The factory alternator stays in place and the kit adds a 400-amp B11348400 second alternator to carry your added electrical loads.
How much power does it add?
The kit adds a 400-amp alternator on top of your factory output — substantial dedicated headroom for inverters, auxiliary batteries, lighting, winches, and audio.
Is the kit complete?
Yes — it includes the dual-alternator bracket assembly, the 400-amp alternator, the drive belt, wiring, and mounting hardware. Follow the included instructions for proper spacer usage and belt alignment.
Cast vs anodized — does it matter?
Functionally they're the same 400-amp alternator. Cast is the lower-cost finish; anodized adds a colored finish. Pick whichever look you want. Every Mechman alternator is built in Knoxville, Tennessee. Optional 1-year, 2-year, and lifetime internal-parts (brushes, bearings, rectifier, regulator) warranty terms are available at checkout.
Need a hand choosing?
Not sure which Duramax kit fits your truck?
Tell us your model year and whether your engine has a vacuum pump, and we'll point you to the right kit.
Trademark Disclaimer: Duramax™ and GM™ are trademarks of their respective owners. All company, product, and service names used here are for identification purposes only and do not imply endorsement or ownership. Mechman manufactures aftermarket charging components compatible with the applications listed.