Top 10 Lml Cp3 Conversion Kits For Duramax: Fleece, Bd, S&s Compared 2026

⚡ Quick Verdict

📋 How We Evaluated

Evaluation focused on build quality, including material durability and hardware completeness. Performance criteria included fueling capability support and compatibility with stock or mild setups. Value also considered warranty terms, emissions claims, and Amazon-style rating signals where available, plus user suitability for DIY versus shop installs.

Fitment	2011-2016 GM 2500/3500 LML Duramax
Kit Type	CP3 conversion kit with CP3
Design Focus	Vehicle-specific replacement hardware
Brand Line	Fleece Performance CP3 Kits

What We Found

Fleece’s FPE-LML-CP3-WP kit is aimed at 11-16 LML 2500/3500 applications, and the listing leans into a vehicle-fit replacement approach. The description calls out quality materials and focuses on parts replacement rather than vague “upgrade” language. That’s helpful when you’re trying to avoid ordering something that only sort-of fits.

One important detail: the value really depends on what “with CP3” means in the complete package, and the provided info here doesn’t include rating or price proof to back up that claim.

Who It’s For

I would shortlist this if you want Fleece’s specialty-built conversion approach and you’re planning a straightforward swap for an 11-16 LML. It fits best when you’re focused on correct mounting/routing and you’re comfortable that the included CP3-related components match your install plan.

This is also a better fit when you already have a clear plan for emissions considerations and line routing for your specific setup.

Fitment	2011-2016 GM 2500/3500 LML Duramax
Kit Type	CP3 conversion kit with HD CP3
Design Focus	Replacement parts built to fit the vehicle
Brand Line	Fleece Performance CP3 Kits

What We Found

This Fleece option targets 11-16 LML Duramax trucks and is described as a “with HD CP3” configuration. The listing’s emphasis is still on replacement-style parts, quality materials, and fitment to the vehicle.

The overall concept is the same as most CP3 conversions – swap away from the factory CP4 platform to a CP3 setup to reduce the risk owners associate with CP4 contamination events. The listing also references components tied to injection hardware/controllers.

In the details provided here, though, emissions legality, warranty coverage, and the exact tuning expectations aren’t made clear.

Who It’s For

I would consider this if you want Fleece’s higher-spec “HD CP3” approach for 11-16 LML applications and you prioritize reliability and consistent pressurization over marketing claims.

It’s a good fit for stock or mild builds where you want a reliability-first conversion, especially if you’re working with an installer who can confirm emissions and line routing specifics.

It also makes sense if you’re trying to buy a single package that includes the upgraded CP3 and the associated hardware.

Fitment	2011-2013 LML Duramax
Kit Type	CP3 conversion kit with Powerflo 750 CP3
Package Weight	25.0 Pounds
Package Quantity	1

What We Found

Fleece Performance Engineering’s LML-CP3-FF-10 kit pairs the conversion with a specific “Powerflo 750 CP3,” and the listing includes package dimensions and weight. That helps, because it signals this isn’t just a lightweight adapter-only buy.

The description continues to treat it as an LML CP3 conversion built around that Powerflo pump pairing, which targets the reliability and fueling stability goals many LML owners are chasing when moving away from the CP4 platform.

What’s missing in the provided details: emissions legality, warranty duration, and whether any calibration steps are expected.

Who It’s For

I’d shortlist this if you want a more clearly defined component pairing – conversion centered on the “Powerflo 750 CP3.” It also fits if you’d rather plan your install around a specific pump model and you want evidence (like the shipment size/weight) that the order is likely to include meaningful hardware.

Best results come when you match the pump pairing to what your fueling and emissions equipment requires – so an installer confirmation still matters.

Fitment	2011-2016 Chevy/GMC 6.6L LML Duramax
Function	Upgrade from CP4 to CP3 for reliability
Materials	High quality with corrosion and oxidation resistance
Package Includes	1x Upgraded Performance CP4 to CP3 Conversion Kit

What We Found

BIGREAT’s kit is built around a CP4-to-CP3 conversion for 2011-2016 LML Duramax trucks in Silverado/Sierra 2500/3500 applications. The listing states a goal to remove the factory CP4 pump and improve reliability and fueling capability using a CP3 platform. It also mentions corrosion/oxidation resistance, positioning the hardware for durable under-hood service.

The package is described as a conversion kit with contents referenced via pictures, but the provided information doesn’t include a clean itemized breakdown, pump model details, warranty terms, or emissions compliance statements.

Who It’s For

I’d consider this for an LML owner looking for a straightforward CP4-to-CP3 reliability upgrade across the 2011-2016 window – especially if corrosion resistance and durable hardware matter to your use case. It’s also a fit if you’re comfortable verifying what’s included based on the images (or confirming with a shop before purchase).

Value will depend heavily on what the kit truly contains and whether your emissions setup stays compatible.

Brand	BD Diesel
Kit Name	Venom CP3 Conversion Kit
Fitment	2011-2016 Chevy/GMC Duramax 6.6L LML
Compatibility Note	With Standard Pump

What We Found

BD Diesel’s Venom CP3 conversion kit is presented with a Venom CP3 platform and a “standard pump” fitment note for 2011-2016 Chevy/GMC 6.6L Duramax trucks.

The listing’s messaging aligns with the common CP3 conversion goal: swap to the CP3 setup to reduce the catastrophic risk associated with CP4 failures and contamination. What I’m not seeing in the provided details is an itemized hardware list.

The listing also doesn’t confirm whether you can expect a tuning-free install or whether ECU calibration will be required. Emissions legality details are also not present here, which limits guidance for any street-driven, emissions-controlled use.

Who It’s For

This works for LML owners who specifically want a BD Diesel-branded CP3 conversion and prefer a “known name” over generic compatibility kits. It’s aimed at 2011-2016 trucks with the “standard pump” condition noted by the seller.

I’d treat it as a good candidate only after confirming emissions compatibility with your local requirements and verifying the full installation parts list with your installer.

Fitment	2011-2016 Chevy Silverado & GMC Sierra 6.6L LML
Includes	Mounting adapter, high-pressure line, fuel fittings, necessary hardware
CP3 Pump Included	No
Goal	Mitigate CP4 catastrophic failures

What We Found

AUTOVIC’s kit is positioned as a complete CP3 injection pump conversion kit for 2011-2016 LML Duramax trucks. The listing explicitly states that it includes a CP3 mounting adapter, a high-pressure line, fuel fittings, and all necessary hardware – while also stating the CP3 pump is not included.

That “pump not included” note helps you plan your shopping list. The kit is marketed as mitigating CP4-related contamination risk, and it even claims high-flow CP3 feed and return fittings.

The main thing missing in the provided details is emissions compliance documentation, warranty coverage, and any clear signals about tuning requirements.

Who It’s For

I would shortlist this if you already plan to source the CP3 pump separately and you want the rest of the hardware handled in one place. The included mounting adapter/line/fittings approach is especially useful if you’re planning a reliable install workflow for both DIY and shop installs.

It’s also a good fit if you’re going reliability-first before a pump failure becomes a bigger problem. Just don’t skip confirming emissions dosing/routing for your setup.

Fitment	2011-2016 GM LML Duramax
Emissions Compliance	50 State Legal / CARB Compliant EO# D-756-4
Tuning Required	No ECU calibration required
Warranty	Two-year, unlimited-mile warranty

What We Found

S&S Diesel Motorsport offers the LML-CP3-CARB conversion, and the listing is unusually direct about the big buyer blockers. It’s described as a more durable plug-and-play replacement for CP4, with a claim that no ECU calibration is required.

The kit also calls out OE fit and function, including a dosing line for emissions equipment and injector priming. On emissions legality, the listing states it is 50-state legal / CARB compliant with EO# D-756-4 – something that many other listings here don’t provide.

It also includes a two-year unlimited-mile warranty, which adds confidence beyond the parts themselves.

Who It’s For

I would recommend this for street-driven LML owners who want a CP3 conversion without ECU tuning and without sacrificing emissions legality. It’s also a fit for installers and DIY setups that prefer plug-and-play behavior with fewer system unknowns, especially where emissions dosing line functionality matters.

If you want the “least paperwork ambiguity” option, this is the one I’d look at first.

Fitment	2011-2016 GM 2500/3500 LML Duramax
Kit Type	CP3 conversion hardware kit without pump
Design Focus	Replacement parts built to fit the vehicle
Brand Line	Fleece Performance CP3 Kits

What We Found

Fleece Performance’s FPE-LML-CP3-NP kit is a hardware-only approach: it’s built for the LML CP3 conversion but specifically excludes the pump. The listing emphasizes replacement parts, quality materials, and fitment to the vehicle.

That “without pump” positioning can be useful if you already own a CP3 or if you plan to choose a pump from a specific supplier. Like other Fleece conversions, it follows the reliability-forward idea of moving away from CP4 using FPE’s CP3 conversion ecosystem.

Still, in the provided details there’s no emissions legality, warranty coverage, tuning requirement, or itemized contents list.

Who It’s For

I would consider this if the CP3 pump choice is already settled and you just need the conversion hardware to complete the swap. It fits both shop installs and DIY installs where pump sourcing is handled separately.

It can also help if you’re trying to control total cost by pairing a known pump with the conversion hardware. Just make sure the emissions/dosing routing and any calibration requirements are aligned with your chosen configuration.

Kit Type	CP4 to CP3 conversion kit with pump
Tuning Required	No modifications required (tuning-free)
Emissions	Emissions intact
Claim	Proven track record for reliable performance

What We Found

Industrial Injection’s LML CP4 to CP3 conversion kit with pump is presented as an emissions-intact option. The listing highlights tuning-free installation by stating no modifications are required, and it positions the conversion as reliable with a proven reputation tied to the brand’s approach.

The product name and description strongly suggest it’s meant to support emissions compatibility while swapping away from CP4. It also uses peace-of-mind language. What’s still missing in the provided details is a detailed hardware list, specific emissions documentation, and warranty terms.

Without those specifics, “emissions intact” can mean different things depending on jurisdiction.

Who It’s For

I’d shortlist this for owners who want a CP3 conversion from a diesel-system parts brand and who care about tuning-free installation. It also makes sense for regulated or street vehicles when you’re aiming for an emissions-intact workflow.

The key is confirmation: buyers should verify local emissions legality and make sure the included hardware matches their emissions equipment configuration.

Kit Part Number	436403
Fitment	11-15 GM 6.6L LML Duramax
Kit Type	Conversion kit with pump
Tuning Requirement	Tuning required

What We Found

Industrial Injection’s 436403 conversion kit with pump targets 11-15 LML Duramax and explicitly states that tuning is required. The listing notes compatibility for a CP4-to-CP3 conversion and mentions American manufacturing.

It frames the kit as a tech-forward conversion hardware option, and “with pump” suggests it supports a fuller swap workflow rather than being hardware-only. The drawback is the tuning requirement, which adds cost, planning, and calibration risk compared to tuning-free alternatives.

In the provided details, emissions legality is only addressed broadly by the conversion intent – there are no specific emissions documentation details shown.

Who It’s For

This is for buyers who are comfortable handling ECU calibration as part of the conversion. It fits 2011-2015 LML Duramax trucks, and it suits shop-led installs where tuning can be handled efficiently by a qualified calibrator.

It’s also a fit if you’re prioritizing the brand’s conversion platform and you don’t mind the extra setup steps as long as local emissions requirements line up.

What to Look For Before Buying

The best CP3 conversion kit for an LML depends on more than “CP4 to CP3.” Start by matching the kit to your exact year and 6.6L LML application, then figure out whether you’re buying a full kit (including the pump) or a hardware-only kit. If you drive on the street, emissions legality and dosing-line support matter as much as the fuel-system reliability goal. Finally, confirm whether the install is truly tuning-free – or if you should budget for ECU calibration – and check the warranty details before ordering.

Check Confirm LML Year and Truck Fitment

I would lock fitment to your exact model years and confirm the listing is actually calling out the 6.6L LML engine variant – not just “Duramax.” CP4-to-CP3 kits can differ by generation and sometimes by emissions setup, so if the listing is vague, ask for compatibility confirmation. If it mentions Silverado and Sierra 2500/3500 configurations, double-check that matches your truck. Before you buy, I’d also confirm the mounting adapter alignment is meant for your truck’s layout.

Value Match Kit Completeness to the Purchase Plan

Some listings include the CP3 pump; others sell the conversion hardware without it. I’d evaluate total cost and total effort – not just the headline price – because a “hardware-only” kit can turn into extra sourcing later. Check for the basics you’ll need for a complete swap: mounting adapter, high-pressure line, fuel fittings, and all necessary hardware. If your truck has emissions equipment, look for dosing-line provisions. Then choose based on whether you’re using a shop or planning the install yourself.

Rating Use Rating Signals and Listing Specifics

When ratings exist, I use them like a fast sanity check for recurring issues like leaks or missing parts. If ratings aren’t available, I lean harder on documentation that actually helps: clear part numbers, a detailed included-components list, warranty terms, and explicit wording about tuning or tuning-free installation. I’d rather see a list of what’s included than a paragraph about materials or “durability” with no build details.

Verify Verify Emissions Legality and Tuning Requirements

For street trucks, emissions legality isn’t optional – it’s the difference between a fix you can run and a conversion that creates problems later. I’d verify any CARB/EO documentation when a kit claims compliance. Also check the listing’s tuning language: some kits claim no ECU calibration is required, while others state tuning is required to match fueling behavior. Align your plan with your local requirements and your installer’s ability to handle any calibration steps.

Frequently Asked Questions

Do LML CP3 conversion kits require ECU tuning?

It depends on the kit design. Some CP3 conversion kits claim tuning-free installation by matching pump output behavior and pairing parts in a way that doesn’t require ECU calibration. Others explicitly require tuning to match fueling targets and injector/priming behavior. Always verify the listing wording and confirm with the installer before scheduling the work.

What emissions equipment concerns matter during an LML CP3 conversion?

Pay attention to how the kit handles emissions dosing-line function and injector priming flow – especially if the listing mentions OE fit and function. Some kits provide clearer compliance documentation and explain what they include for emissions equipment. Others use broader phrases like “emissions intact” without listing the documentation or wiring/line specifics. I would confirm coverage with your emissions setup and local requirements.

Should a CP3 kit include the CP3 pump or be hardware-only?

Hardware-only kits can make sense if you already have the correct CP3 pump picked out, since you can avoid duplicate purchasing. Full kits (with the pump included) can simplify ordering and reduce compatibility mistakes. Pump inclusion also affects total cost and lead time, so match the pump type to the kit’s intended output behavior and check whether any tuning is required for your setup.

How does a CP3 conversion reduce CP4 failure risk?

The basic idea is that a CP3 swap replaces the factory CP4 platform that some owners associate with catastrophic failures and contamination events. The conversion is meant to use a more reliable pump architecture for long-term operation. A good kit also supports correct line routing and safe pressure delivery. Reliability still depends on clean fuel-system prep and correct installation.

What warranty and documentation should be checked before buying?

I would check for two things before buying: warranty terms and emissions documentation. Warranty coverage helps you gauge manufacturer confidence for parts inside high-pressure systems. For street vehicles, look for CARB/EO numbers or other clear compliance documentation. If ratings and prices aren’t available, documentation and part-number specificity become even more important because you’re relying on the listing’s details.

🎯 Final Verdict

If I’m picking the “best CP3 conversion kit for LML” based on what’s explicitly stated, I’d go with S&S Diesel Motorsport. The listing calls out no ECU tuning, includes an emissions dosing line for emissions equipment, and states 50-state/CARB compliance under EO# D-756-4 – plus it includes a two-year unlimited-mile warranty. Industrial Injection is close on the concept of tuning-free, emissions-intact conversion, but the provided details don’t give the same level of compliance specificity. Bottom line: choose S&S for the clearest on-road confidence, then confirm fitment and emissions setup compatibility before ordering.