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This rear transverse transaxle gearbox is designed and manufactured for the latest GT car applications where the vehicle package requires the cluster to be behind the differential. This gearbox is in particular suitable for mid engine cars although it can also be configured for front engine cars.  It is a customer specification transverse gearbox ideally suited for GT3 cars requiring extended mileage between maintenance intervals, heavily based on Xtrac’s successful P626 & P529 Le Mans winning gearbox family.

All components have been verified by classical and finite element analysis (FEA) to known, proven duty cycles and safety factors. The gearbox is ideally sized for the latest generation of smaller capacity turbo charged engines used in GT racing as well as the traditional larger capacity normally aspirated engines.

The gearbox has been extensively validated using Xtrac’s range of R&D test bench equipment including an optimised oil system developed using Xtrac’s gearbox in the loop simulator.

The resultant design allows gear cluster changes without disassembly of the rear of the car. Gear changes are performed using Xtrac’s positive and reliable sequential gearchange mechanisms which are compatible with all leading AGS suppliers and the optional P1254 Integrated Valve Actuator (IVA) gearchange system.

Xtrac’s legendary record for reliability and performance has been built on multiple 24 hour race wins at races such as Le Mans, Nürburgring, Spa and Daytona.


  • 800Nm (590lbf ft) maximum engine input torque.
  • 1st and 2nd layshaft gears are integral, 3rd to 6th are slide on with a wide range of available ratios.
  • Gearbox maincase material is magnesium RZ5 and all casting joint faces have ‘O’-Ring seals.  Minimal number of casings and split lines with side covers manufactured from aluminium alloy L169.
  • Differential is the Xtrac plate limited slip differentials with a choice of positive preload settings between 0-200Nm and a range of differential ramp and cross pin angles.
  • Straight cut final drive 15:50, 15:48 & 16:47 are available as standard.
  • Clutch shaft to suit customer installation is included.
  • Hard cut Klingelnberg cyclo palloid bevel set, 21:23, 21:22 & 22:21 are available as standard.
  • Xtrac manufactured output flanges are included to suit GI 87 size tripode joints.
  • Lubrication is via single stage lubrication pump with two filtered scavenge pick ups.
  • Components are manufactured in Xtrac’s own grade of steel (X36C). Bevel sets, final drives and pinions are manufactured in Xtrac’s vacuum melted steel (XVAR1) for longer
    life. Highly stressed components are shot peened.
  • Gearbox weight 56-62kg (123-137lb); depending on specification.

The Gearbox Offers The Following Benefits

  • Very short package with good weight distribution and a low centre of gravity (C of G). Crank height to gearbox output height of 87mm ideal for road car based GT cars.
  • Light, positive gearchange with polynomial barrel tracks.  Overlapping gearchange barrel enabling near seamless gearshifting.
  • Non structural casing with integral mounts to enable easy configuration to suit the customer’s rear subframe and mounting system.
  • Variable right hand output flange Y dimension thus enabling the across output flanges width of the gearbox to be optimised for each particular installation.
  • Full differential mapping simulation data is available from Xtrac’s award winning QT-DTR differential test rig to enable rapid car set up.
  • Quick change gear ratios.
  • Optimised oil system requiring minimal oil levels with excellent performance across the whole lateral and longitudinal g-g vehicle operating envelope.
  • Threaded bosses for oil temperature and pressure sensors.
  • Service interval of 9,000km between rebuilds (GT3 application).
  • Parts available from stock in the UK and the USA thus reducing the need for the customer to carry spare parts.
  • Cost effective, reliable solution.

Options Summary

  • Gear ground and super polished ratios (Xtrem process) are available.
  • Separate bellhousing / engine spacer to suit the customer’s vehicle, engine and clutch installation.
  • MagCanica torque sensing clutch shaft system to suit the vehicle installation to enable precise engine torque measurement which can be so useful for vehicle performance development.
  • Alternator drive, mounting and adjuster to suit a MES alternator or a customer specified alternator.
  • Integrated pneumatic shift cylinder operating the ratchet system.
  • Gearbox configured without a ratchet system to use Xtrac’s P1254 Integrated Valve Actuator (IVA) gearchange system.
  • Aluminium alloy L169 maincase.
  • Dog ring inspection ports.
  • Output flanges with mounting features to accommodate Xtrac’s patented ‘bolt on’ tripode housings.
  • Positive preload adjustment system for the differential using either a mechanical adjuster or a gas pre-load adjuster system.
  • Viscous Combined Plate (VCP) differential.
  • Layshaft speed sensor trigger and sensor housing.
  • Output flange speed sensor triggers and sensor housings.
  • Gearchange barrel potentiometer.
  • Oil pressure and temperature sensors.

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