Overview
The ZF 4143.020.257 2 HL 290 Hydrostatic Drive Assembly is a complete, factory-matched unit designed to manage variable-speed power delivery in heavy-duty ZF transmissions. This assembly integrates the hydraulic pump and motor within a single housing, converting engine torque into smooth, infinitely variable output for off-highway vehicles. As a direct replacement for the OEM part, SKU 4143.020.257 sits at the core of the HL 100 and HL 270 series, controlling forward and reverse travel without clutch wear. When replacing this unit, technicians often inspect the surrounding 4143101046: HOUSING and 4143301055: HOUSING for cracks or distortion, as these components seal the hydrostatic circuit. The assembly is precision-balanced to minimize vibration and ensure consistent oil flow under load.
Symptoms of Failure
- Erratic or surging travel speed: When the hydrostatic drive assembly loses internal seal integrity, the vehicle may lurch or fail to maintain a steady speed, especially during low-speed maneuvering.
- External oil leaks near the pump-motor interface: Worn O-rings or housing cracks cause hydraulic fluid to weep from the joint between the drive assembly and the 4143298040: CASE, leaving puddles under the transmission.
- Whining or grinding noise during direction changes: Contaminated fluid or worn bearings inside the 2 HL 290 produce a high-pitched whine when shifting from forward to reverse.
- Complete loss of drive in one direction: A seized piston or failed swashplate within the hydrostatic unit can stop all power transfer, requiring immediate replacement of the 4143.020.257 assembly.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number / SKU | 4143.020.257 |
| Assembly Type | 2 HL 290 Hydrostatic Drive (Complete Unit) |
| OEM Reference | ZF 2 HL 290 / HL 100 / HL 270 |
| Housing Material | High-strength cast iron (GGG-40) |
| Dry Weight | Approx. 38 kg (83.8 lbs) |
| Overall Dimensions (L x W x H) | 420 mm x 280 mm x 240 mm |
| Max Operating Pressure | 420 bar (6,090 psi) |
| Fluid Capacity (internal circuit) | 1.8 liters |
| Mounting Bolt Torque | 85 Nm (62.7 lb-ft) |
Compatibility
This hydrostatic drive assembly is engineered for ZF transmissions in the HL 100 and HL 270 series, commonly found in telehandlers, wheel loaders, and agricultural tractors. It directly replaces units in the following ZF models: WG180, WG200, WG210, WG220, and WG240. The 2 HL 290 variant is also backward-compatible with earlier HL 80 series when used with the correct 0631329135: SPRING PIN for linkage alignment. Always verify the spline count and port orientation against your existing assembly before installation.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4143101046 | HOUSING | Encloses the hydrostatic pump and motor assembly |
| 4143301055 | HOUSING | Rear housing supporting the output shaft bearings |
| 4143298040 | CASE | Main transmission case that houses the gear train |
| 0631329135 | SPRING PIN | Secures control linkage to the swashplate |
| 0501214034 | SEALING CAP | Prevents debris ingress into the hydrostatic port |
| 0636101024 | CAP SCREW | Fastens the drive assembly to the transmission case |
| 4475280099 | SCREW PLUG | Seals the fill and drain ports on the housing |
| 0634303266 | O-RING | Provides a hydraulic seal between mating flanges |
| 0501200072 | VENT VALVE | Relieves internal pressure and prevents vacuum lock |
| 0501217673 | LUBRICATING NIPPLE | Allows grease injection for the drive shaft spline |
