Dynaflex 37-4035 | 4" O.D. to 3.5" I.D. Exhaust Reducer | 7" OAL | Made in USA

Engineered for precision transitions in heavy-duty exhaust systems, the Dynaflex 37-4035 is the industrial standard for reducing pipe diameters. Proudly Made in the U.S.A., this heavy-wall reducing coupler is designed for fabricators and fleet technicians who require a durable, weld-ready solution for Class 7 and 8 trucks, as well as industrial equipment.

Product Overview

Constructed from high-quality 16-gauge carbon steel, this 7-inch reducer provides a rugged bridge between 4-inch and 3.5-inch exhaust components. The 16GA (.065") wall thickness ensures the structural integrity needed to withstand high-heat cycles and the mechanical stresses of commercial diesel applications.

• Configuration: 4" O.D. to 3.5" I.D.

• Overall Length: 7.0"

• Material: 16 Gauge Carbon Steel

• Origin: Proudly Made in the U.S.A.

Key Features

• Precision Slip-Fit Design: * The 4.0" O.D. end fits inside a standard 4" I.D. pipe or muffler inlet.

  • The 3.5" I.D. end is expanded to slip directly over standard 3.5" O.D. exhaust piping.

• Gradual Taper: The 7-inch overall length allows for a smooth reduction in diameter, which minimizes exhaust turbulence and backpressure compared to shorter, "stubby" adapters.

• Weld-Ready Performance: Ships in a raw, unfinished state. This is the preferred finish for professional fabricators, allowing for immediate, high-penetration welding without the toxic fumes or surface prep required for aluminized or galvanized steels.

• Industrial Durability: Dynaflex manufacturing ensures industrial-grade tolerances and perfectly round ends for a leak-free seal when clamped or welded.

Specifications Table

Applications

• Heavy-Duty Trucking: Adapting 4" turbo downpipes or muffler outlets to 3.5" secondary piping.

• Industrial Power: Connecting commercial generator exhaust ports to ventilation systems.

• Custom Fabrication: Building high-flow custom exhaust systems for diesel performance.

Tech Tip: Because this part is raw carbon steel, it is ready for welding out of the box. To ensure a long service life and prevent external surface oxidation, we recommend applying a high-temperature ceramic or exhaust paint after the installation is complete.