Wehrli 100129 3.5 inch Down Pipe | 2017-2025 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

Features:

• 3.5-inch diameter for better exhaust flow
• Replaces crushed factory downpipe section
• High-temp black ceramic coated finish
• Heat wrap installed for thermal protection
• Emissions compliant, no tuning required
• Connects to factory 4-bolt flange system
• Includes sensor bungs for OEM compatibility
• Improves throttle response and turbo efficiency
• Fabricated steel construction for durability
• Made in the USA

Improved Exhaust Flow for GM 6.6L Duramax

If you’re looking to free up exhaust flow on your L5P Duramax without getting into tuning or emissions issues, the Wehrli 3.5" Down Pipe is one of the smartest upgrades you can make. Designed for 2017–2025 Silverado and Sierra 2500HD/3500HD trucks with the 6.6L Duramax, this pipe replaces the restrictive, crushed factory unit with a high-flow, emissions-compliant solution that bolts right in. From a performance standpoint, the factory downpipe is a known bottleneck. It’s pinched and bent in a way that restricts flow, especially as exhaust gas volume increases under load or during towing. Wehrli solves that with a smooth, full 3.5-inch pipe that maintains consistent diameter throughout. That means better turbo efficiency, quicker spool, and improved throttle response—especially when paired with other upgrades like piping kits or tuning down the road.

High-Quality Construction with Direct-Fit Install

The construction is exactly what you’d expect from Wehrli. It’s fabricated from quality steel, then finished in a high-temp black ceramic coating to handle the intense heat coming off the turbo. On top of that, they’ve already pre-installed a heat wrap around the pipe, which helps cut down underhood temperatures and protects surrounding components. It’s a clean, professional-grade finish right out of the box. Installation is straightforward. This pipe connects directly to the DOC (Diesel Oxidation Catalyst) outlet flange and mates up with the factory front pipe using the OEM-style 4-bolt flange. No tuning is needed, and it retains compatibility with your emissions system. All sensor bungs are in place, so everything functions just like stock—with the added benefit of better flow and sound.

Fits: 2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024, 2025 GM 6.6L Duramax