This fully automatic transmission has been developed under contract to the UK MoD, to be interchangeable with the TN37 transmission installed in the Challenger 1 MBT. The TN54 is now in production for the Challenger Armoured Repair and Recovery Vehicle and for the Challenger 2 MBT which are now in service with Qatar and the UK.

The TN54 has a single input and two in-line outputs at right angles to the input. Drive is transmitted from the engine through a splined coupling to a torque converter. The gear and direction of travel are engaged by correctly sequenced application of multiplate clutches, actuated hydraulically and controlled by electro-solenoid valves. The TN54 transmission features six forward and two reverse gears, a hydrostatic double-differential steering system and integral oil-cooled multiplate main vehicle and parking brakes.

The transmission has integral filtered lubrication and hydraulic systems. A Power Take-Off (PTO) for power pack cooling fans is mounted on top of the main casing.

Alternatively the transmission is supplied with a mechanical steer unit incorporating controlled slip multiplate clutches.

TN54 is also available to suit transversely mounted engines and in this designation it is known as the TN54U.

• DB-1500

This has been developed as a private venture and is an uprated version of the TN54.

In production for Challenger Armoured Repair and Recovery Vehicle and Challenger 2 MBT. In service with Oman and the UK. By mid-1999, over 450 TN54 transmissions had been built.