Performance Delta

Differential-Swaps

Whether you drive an MX-5 NA, NB, NC or ND, an RX-8 or a Fiat 124 Spider, the right gearbox and final drive ratios can transform how your car drives. For short-course racing such as hill climbs, sprints and circuit racing, the standard ratios are often too long, and you might favour quicker acceleration over maximum top speed.

There's more interchange across the range than most people realise. NA and NB cars can take RX-7 ring and pinions plus a range of 3rd party ratios. The NC can take the larger and stronger 8" pinion RX-8 diff with the correct driveshafts. The ND and Fiat 124 Spider share the same platform, so their diffs are interchangeable. For the NC we can also offer a hybrid gearbox using the Fiat 124 gearset in the MX-5 NC casing, or a Jaguar ZF 8HP45 8-speed automatic, which bolts straight on to the NC's MZR engine.

Pick your car and have a play with the calculator below to see what works for you.

Choose your car

Gearbox and wheel details

rpm
mm
%
in
Compare with another setup
Uses the same car, tyre size and max RPM. Shown as a dashed orange line on the graph.
Calculated top speed

—

Tyre size —
Tyre diameter —
Speed per 1,000 rpm (top gear) —
Cruise RPM at 70 mph —
Gear Ratio Overall Max speed Per 1,000 rpm RPM after shift
Important

Calculated speeds are theoretical and based on the stated gear ratios, final drive ratio, engine rpm and nominal tyre size. Actual road speeds differ slightly with tyre growth under load, tyre brand and model, wear, pressure, torque-converter slip and speedometer accuracy. Swap and conversion options may need additional parts, so get in touch to check fitment for your car.

Speed by gear

RPM against road speed

Selected setup

  • Car—
  • Gearbox—
  • Final drive—
  • Tyre—
  • Tyre circumference—
  • Max RPM—

Need parts for your setup?

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