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T304 or T409 Exhaust System? What is the Difference?


T304 or T409… they’re both stainless, right?

Not exactly. We know there are many differences between T304 and T409 exhaust systems, and they should definitely be considered before making purchases.

The three main things one should look for in purchasing exhaust systems are:

  • Corrosion Resistance
  • Finishing Quality
  • Price

Corrosion Resistance: T304 is classified as an austenitic stainless steel (consisting mainly of a nonmagnetic solid solution of ferric carbide or carbon in iron, used in making corrosion-resistant steel). T409 is classified as a ferric grade of steel (containing iron). T409 contains a lower chromium content of steel. Because of the differences in composition, T304 stainless provides superior resistance to the corrosive agents found in exhaust emissions and certain environments.

Finishing Quality: For those interested in the aesthetic features, the T304 exhausts have a mirror-like polished finish. T409 stainless exhausts typically have a matte finish.

Price: The last point is price. As mentioned earlier, T409 has a lower grade of steel that is significantly less expensive to produce, which results in a lower cost then T304 products.

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The Diesel Performance Experts