Mazda RX7 FD (FD3S) Rebuilt Rear Diff – Rare 3.9 Spirit R Ratio

Mazda RX7 FD (FD3S) Rebuilt Rear Diff – Rare 3.9 Spirit R Ratio

Suits: Mazda RX7 FD (FD3S)
Ratio: 3.9 (Rare Spirit R Factory Ratio)
Carrier Type: Factory Helical / Torsen Style LSD
Upgrade: Solid Pinion Bearing Spacer Upgrade

Upgrade your FD RX7 with this fully rebuilt rear differential featuring the rare 3.9 ratio from the Spirit R model. This ratio offers an excellent balance between acceleration and highway drivability, making it highly sought after among rotary enthusiasts.

This unit retains the factory helical (Torsen-style) LSD, providing smooth, progressive torque transfer without the harsh engagement of clutch-type LSDs.

Key Features:

Complete Rebuild:
Fully stripped, inspected, and rebuilt using all new high-quality bearings and genuine Mazda seals.

Rare 3.9 Spirit R Ratio:
Hard-to-find factory gearing offering good acceleration while maintaining comfortable cruising RPM.

Factory Helical / Torsen LSD:
Smooth torque biasing differential for predictable handling and excellent street performance.

Solid Pinion Bearing Spacer Upgrade:
Replaces the factory crush sleeve for improved strength, durability, and consistent preload under high load.

Refinished Housing:
Comes with vapour blasted rear cover and gold zinc plated bolts for a clean OEM+ finish.

This is the ideal option for:

• Spirit R style builds

• Street-driven FD RX7s

• Mild to high power 13B turbo setups

• Drivers wanting smooth LSD operation without clutch chatter

Professionally assembled and ready to install.