Home » 2015.5-2016 Chevy/GMC Duramax LML 4" DPF & CAT Delete Pipe(With Muffler)

Compatibility: 2015.5–2016 Chevrolet / GMC Duramax 6.6L LML

Product: 4" DPF & CAT Delete Pipe System

LEGAL DISCLAIMER & COMPLIANCE

OFF-ROAD USE ONLY: This high-performance racing component is engineered exclusively for competition or sanctioned off-road use. It does not comply with federal or local emissions laws for highway operation. Installation on any vehicle registered for public roads is strictly prohibited. The end-user assumes all legal liability and risk associated with the installation and use of this product.

PHASE 1: DISASSEMBLY & OEM REMOVAL

Step 1: Sensor & Connection Preparation Carefully remove all EGT and pressure sensors from the factory exhaust tubing. Loosen the primary flange securing the stock downpipe to the DPF/exhaust assembly.

Step 2: DPF Unit Extraction

  1. Disconnect all factory electrical plugs and ventilation lines from the Diesel Particulate Filter (DPF). Secure unused harnesses to the truck frame or remove them from their mounting clips.

  2. Lubricate the exhaust hangers with WD-40 or a silicone-based spray. Pry the hangers from the rubber isolators and remove the factory DPF unit from the vehicle.

Step 3: Primary Downpipe Removal

  1. Flange Hardware: Use a 15mm socket to unscrew the 3-bolt flange that connects the OEM turbo direct pipe to the factory downpipe.

    • Note: Retain the OEM nuts, as they are required for the installation of the new system.

  2. To facilitate easier removal of the stock downpipe, detach the hanger secured to the transmission housing. If space is limited, cutting the factory pipe inlet may be necessary for extraction.

PHASE 2: COMPONENT INSTALLATION

Step 4: Installation of Downpipe #1 (3-Bolt Flange) Align the 3-bolt flange of the new Downpipe #1 with the turbo direct pipe flange.

  1. Secure the connection using the original hardware and the OEM nuts saved from Step 3.

  2. Tech Note: Apply downward pressure to seat the flange correctly. Tighten sufficiently to secure the pipe while allowing enough play for final alignment.

  3. Re-secure the support hanger to the transmission housing using the original bolts.

Step 5: Intermediate Pipe #2 Integration Connect the beveled/sloped end of Pipe #2 to the outlet of Downpipe #1. Secure loosely with the provided clamp. Simultaneously insert the integrated hangers into the OEM rubber isolators.

Step 6: Muffler Replacement & Wheelbase Adjustment

  1. Connect the Muffler Replacement Pipe (#3) to the first section of the factory over-axle pipe.

  2. Wheelbase Configuration:

    • For EC/SB (Extended Cab / Short Bed) models with a 143-inch wheelbase, you must trim approximately 8 inches off the non-expanded (straight) end of Pipe #2.

    • Always measure twice before cutting to ensure a precise fit for your specific chassis.

PHASE 3: FINAL ALIGNMENT & TORQUE

Step 7: Sequential Tightening Perform a final visual inspection to ensure the system clears all chassis components, cables, and heat shields.

  1. Starting at Pipe #1 (Downpipe), tighten the 3-bolt flange hardware and V-band clamps.

  2. Proceed gradually toward the rear of the vehicle, tightening each joint and clamp while verifying adequate clearance at every connection point.

POST-INSTALLATION ADVISORY

  • ECM Tuning: This hardware modification requires a compatible Electronic Calibration (Tune) to disable the factory emissions logic. Without software modification, the vehicle will enter "Limp Mode."

  • Thermal Check: Re-torque the 3-bolt flange and all pipe clamps after the first 50–100 miles of driving to account for material settling and thermal expansion.