Is there a 6-speed transmission available for the Mazda RX-7 FD?

Mazda never offered a factory 6-speed transmission for the FD RX-7. However, if you are looking to do a conversion, there are several aftermarket and OEM swap options available depending on your power goals, budget, and fabrication skills.

A 6-speed conversion is generally a Hard to Expert level task, as none of the options are direct drop-ins. Here are the most common routes:

1. Tremec T-56 Swap

For high-horsepower builds, swapping in a Tremec T-56 (often sourced from an F-Body Camaro or Trans Am) is highly recommended. It requires a custom adapter plate or spacer to bolt up to the 13B-REW block ¹¹. The T-56 is very stout and features a wide powerband with an excellent double-overdrive for highway cruising, though you will have to custom-tailor your clutch setup and driveshaft ⁴.

2. RX-8 6-Speed Swap

You can physically fit a 6-speed from a Mazda RX-8, but it is generally not recommended for the FD. The RX-8 6-speed is notoriously weak and will likely break under the torque of a turbocharged 13B-REW ⁶.

If you still want to pursue this route for a lower-power setup, it requires significant custom work:

• Fabrication: You will need to modify or fabricate the Power Plant Frame (PPF) and the transmission cross-member.
• Driveline: A custom-length driveshaft and a Turbo II style clutch and starter are required.
• Speedometer: The RX-8 transmission does not have a mechanical speedometer drive. You will need to use a GPS-based speedometer, such as a Speed Hut gauge, or a conversion box like a Cable X ⁴.

3. High-End Aftermarket & Racing Gearboxes

There are premium, custom-built 6-speed transmissions and dogboxes available from companies like HKS, Trust/Greddy, Knight Sports, Quaife, and Hewland ⁸.

• Cost: These are extremely expensive, often starting around $7,000 and easily reaching $20,000+ for a fully built setup ¹.
• Maintenance: Dog-engagement boxes shift incredibly fast but wear quickly and require frequent rebuilds. They are also noisy and harsh, making them suited for dedicated road racing rather than street driving.

To help narrow down the best option, what are your horsepower goals, and is the car being built primarily for the street or the track?