The Renk HSWL 284 transmission is a hydromechanical power shift, reversing and steering transmission with four gears forward and four reverse. It was installed in the now cancelled 155 mm SP-70 and various trials vehicles such as the MaK Keiler fast mineclearing tank.

Following trials with prototype vehicles a total of 24 production Keiler vehicles were ordered from MaKwith final deliveries being made to the German Army early in 1998. This transmission is designated the HSWL 284M.

A more recent version of the HSWL 284 is installed in the Krauss-Maffei Wegmann 155 mm/52 calibre PzH 2000 self-propelled artillery system, of which 185 systems have been ordered by the German Army with first deliveries made in July 1998 and production expected to continue through to the year 2002.

The transmission can be operated fully automatically or semi-automatically and can be mounted to the engine directly or via a connecting component. The output shafts are transverse to the input.

Propulsion drive is via a torque converter with lock-up clutch, shifting and reversing gear to be shifted under load with planetary gear sets, multidisc brakes and clutches.

Steering drive is infinitely variable by a hydrostatic-hydrodynamic superimposed steering system. The transmission brake is a hydrodynamic retarder at the transmission output shaft as part of the vehicle brake system.

Controls include electric remote control for gearshifting and reversing, mechanically or hydraulically actuated steering, mechanical actuating of the emergency drive second forward gear and reverse gear when the current fails. A power take-off from one of the two cooling fans is provided.

Options for the HSWL 284 automatic transmission include connecting cable between gear selector, electronic control unit, transmission and vehicle, output gear-type couplings, final drives, sprocket drums, brake actuating system and external testing device.

The latest versions are the HSWL 284 C and the HSWL 294. The former has been installed in both prototypes of the Panzerhaubitze 2000 built to meet the requirements of the German Army, the 155 mm PzH 2000 self-propelled howitzer system in an L-power pack configuration. Prototypes for transverse-mounted power packs are under consideration. The HSWL 294 will also be installed in a Chieftain MBT as a retrofit kit. The design of the HSWL 284 C and the HSWL 294 is similar, with the former rated at a maximum of 900 kW and the latter at 1,100 kW. They also have power take-offs for driving the cooling fans which incorporate hydrodynamic couplings. These can be used to disconnect the fans when a vehicle accelerates, thereby reducing very significantly the drag due to the inertia of its rotating parts, in addition to providing infinitely variable control of the fan speed. The combined brake system (retarder, service and parking brake) including the hydraulic control, is arranged at the transmission.

In production for Keiler mineclearing system based on modified M48 tank chassis (24 vehicles ordered by the German Army with MaK being prime contractor) and 155 mm PzH 2000 (185 vehicles ordered by the German Army with Krauss-Maffei Wegmann as prime contractor and MaK being responsible for the chassis).