4"/5" 2017-2019 L5P 6.6 Duramax DownPipe Back Exhaust

4” / 5” Downpipe-Back Exhaust System

2017–2019 Duramax 6.6L L5P (Chevy / GMC)

*Race and off-road use only*

Upgrade exhaust flow and sound on your 2017–2019 L5P Duramax with this 4” or 5” downpipe-back exhaust system, manufactured by SPELAB and independently retailed by Secret Diesel Performance.

This system replaces the restrictive factory exhaust from the downpipe back, helping reduce backpressure and improve overall exhaust efficiency. Designed for off-road, towing, and performance-oriented builds, it delivers a deeper, more aggressive exhaust tone while providing a solid foundation for future performance upgrades.

Built with durability and proper fitment in mind, the modular design allows for straightforward installation and reliable long-term performance.

Features & Benefits

• Downpipe-back exhaust system for 6.6L Duramax L5P
• Available in 4” or 5” diameter configurations
• Improved exhaust flow and reduced backpressure
• Deeper, more aggressive exhaust tone versus stock
• Direct replacement for factory exhaust components
• Designed for race and off-road performance use

Fitment

• 2017–2019 Chevrolet Silverado 2500HD / 3500HD
• 2017–2019 GMC Sierra 2500HD / 3500HD
• 6.6L Duramax L5P

Important Notes

• Intended for race and off-road use only
• Not legal for use on public roads in some states
• Professional installation recommended
• Product is independently retailed and not affiliated with or endorsed by the vehicle manufacturer