Black 3'' Downpipe Exhaust For 2011-2016 LML 6.6L Duramax Diesel Chevrolet GMC 2500HD 3500HD

What Does a Downpipe Do?

The stock downpipe on your 6.6L LML Duramax creates severe exhaust restriction, causing backpressure, turbo lag and high EGTs. Our 3-inch high-flow catless downpipe replaces the restrictive factory unit, optimizing exhaust gas flow, speeding up turbo spool, lowering operating temperatures, and unlocking reliable performance gains for daily driving and heavy towing.

Product Specifications

• Engine: GM Duramax 6.6L LML Turbo-Diesel 2015.5-2016
• Pipe Diameter: 3 inch
• Material: Stainless Steel
• Surface: Mirror Polish
• Configuration: Catless
• Flange Type: Bolt-on (4-Bolt) with O2 sensor bung
• Weight: 2.32 kg (2320 g)

Key Features

• Larger internal diameter than stock for dramatically increased exhaust flow
• TIG-welded stainless steel construction with mirror polish
• Reduces turbo lag and enhances throttle response
• O2 sensor bung included for sensor retention
• Direct bolt-on to the factory turbocharger

What's Included

• Downpipe
• Gasket(s)
• O2 sensor bung
• Mounting hardware

Check Before Choosing

• Cab & Chassis exclusion: Will NOT fit Cab & Chassis trucks — only fits pickup models (2500/3500HD).
• Tune required for delete: Yes — a diesel tune (EFI Live / HP Tuners) is required to clear the CEL/DPF codes and safely manage the increased flow on the LML.
• Street legality: No — not CARB or EPA certified. Off-road / competition use only.
• EGT effect: Lowers exhaust gas temperatures under sustained load — a key benefit for towing and hard driving.

• 2015-2016 Chevy Silverado / GMC Sierra 2500HD & 3500HD 6.6L LML Duramax Diesel

Installation Guide

Pre-Installation Checklist

• Confirm your engine code and model year match the fitment list above
• New gaskets and mounting hardware ready
• 22mm slotted O2 sensor socket + PB Blaster on hand
• a diesel tune (EFI Live / HP Tuners) to clear CEL and DPF codes

Installation Steps

1. Lift the vehicle and secure it on jack stands
2. Soak the O2 sensors and flange bolts with PB Blaster for 30+ minutes
3. Unplug and remove the O2 sensors with the slotted socket
4. Remove the factory downpipe and discard the old gasket
5. Bolt on the new downpipe with a fresh gasket
6. Reinstall and reconnect the O2 sensors
7. Flash your tune to suppress the check engine light

Installation Notes

• Never reuse the old gasket — it will cause an exhaust leak
• Use a slotted O2 socket, not a wrench — the sensor threads strip easily
• A catless downpipe triggers a CEL until the ECU is tuned
• Expect a stronger raw exhaust smell (normal for catless)

FAQ

Does it fit Cab & Chassis trucks?

No — this SKU is for pickup models only. Cab & Chassis requires a different SKU.

Do I need a tune on the LML?

Yes — a diesel tune is required to clear the CEL/DPF codes and safely manage increased flow.

Will it lower my EGTs?

Yes — reducing back-pressure lowers exhaust gas temperatures under load, which is a key benefit for towing.

Is it street-legal?

No — not CARB or EPA certified. Off-road / competition use only.