Upgrading the Transmission for High-power Rx-7 Ls Swaps: Clutch and Gearbox Choices

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The Mazda RX-7 is a beloved sports car, known for its lightweight design and exceptional handling. However, when it comes to swapping in a high-powered LS engine, one of the most critical upgrades is the transmission. In this article, we will explore the best clutch and gearbox choices for high-power RX-7 LS swaps, ensuring that your setup can handle the increased power and torque.

Understanding the Transmission Needs for LS Swaps

When upgrading to an LS engine, the stock RX-7 transmission is often inadequate. The LS engine produces significantly more torque than the original rotary engine, necessitating a robust transmission system. The choice of clutch and gearbox will directly impact performance, reliability, and driving experience.

Key Factors in Transmission Selection

  • Torque Capacity: Ensure the transmission can handle the torque output of the LS engine.
  • Weight: A lighter transmission can improve overall vehicle dynamics.
  • Gear Ratios: Choose gear ratios that complement the power band of the LS engine.
  • Ease of Installation: Some transmissions may require more modifications than others.
  • Cost: Budget constraints will influence your choices significantly.

Several gearbox options are popular among enthusiasts for their compatibility and performance with LS-swapped RX-7s. Here are some of the top choices:

  • T56 Transmission: A favorite for its strength and wide gear ratios, the T56 is a six-speed manual transmission that can handle high horsepower applications.
  • TR6060 Transmission: An evolution of the T56, the TR6060 offers improved durability and is commonly found in modern muscle cars.
  • TH400 Transmission: For those preferring an automatic option, the TH400 is a three-speed transmission known for its robustness and reliability.
  • 6L80E Transmission: This six-speed automatic transmission provides excellent performance and is well-suited for high-power builds.

Choosing the Right Clutch

The clutch is just as important as the gearbox when it comes to handling the power of an LS engine. Here are some factors to consider when selecting a clutch:

  • Clutch Material: Options include organic, ceramic, and metallic materials, each offering different performance characteristics.
  • Clutch Size: Ensure compatibility with the chosen transmission and ensure it can handle the power output.
  • Pressure Plate: A stronger pressure plate can provide better engagement and hold more power.
  • Single vs. Twin Disc: Twin disc clutches can handle more power but may require more effort to operate.

Here are some highly regarded clutch options for RX-7 LS swaps:

  • Spec Stage 2+: This clutch offers a good balance of performance and streetability, making it suitable for both daily driving and track use.
  • McLeod RST: Known for its smooth engagement and high torque capacity, the RST is a popular choice for high-power builds.
  • Clutch Masters FX400: This clutch is designed for high-performance applications and can handle significant power without sacrificing drivability.
  • Exedy Stage 1: A great option for those looking for a reliable and affordable clutch that can handle moderate power increases.

Installation Considerations

Installing a new transmission and clutch in an RX-7 can be a complex task. Here are some considerations to keep in mind:

  • Bellhousing Compatibility: Ensure that the bellhousing matches the LS engine and the chosen transmission.
  • Driveshaft Modifications: You may need to modify or replace the driveshaft to accommodate the new transmission.
  • Crossmember Adjustments: The transmission crossmember may require repositioning or replacement.
  • Clutch Hydraulics: Consider upgrading the clutch master and slave cylinders for better performance.
  • Wiring and Electronics: Ensure that any necessary wiring modifications are made for the LS engine and transmission.

Final Thoughts

Upgrading the transmission for a high-power RX-7 LS swap is essential for maximizing performance and reliability. By carefully selecting the right gearbox and clutch, you can ensure that your setup can handle the demands of increased power while providing an enjoyable driving experience. Whether you choose a manual or automatic transmission, make sure to consider the factors outlined in this article to make an informed decision.