The P1389 gearbox is Xtrac’s fourth generation of IndyCar transmission, continuing the line of quality, performance and reliability that are Xtrac’s hallmarks. A complete makeover of the successful P1011, the P1389 offers a significant weight reduction with new casing designs specifically tailored to a switch to lightweight Magnesium.

Drive is fed from the engine directly to the gear cluster before returning forwards to a full form ground fixed ratio bevel set. The bevel wheel in turn drives a spur final drive, which can be tuned for the variety of circuits encountered in the Indycar Series. In standard configuration a final drive wheel is mounted on a Nitrogen Charged Adjustable Preload differential, whilst for the ovals this is replaced with a lightweight spool with integral output flange.
Gear changes are performed using Xtrac’s, new, in-house developed, Electric Servo Actuator (ESA).

Xtrac’s legendary record for reliability and performance is built by products like this, which have won multiple Indy 500 victories, in fact every ‘500’ since 2000.