Overview
The ZF 4143.020.222 2 HL 250 Hydrostatic Drive Assembly is a complete, high-pressure hydraulic unit designed for precise speed and torque control in heavy-duty ZF transmissions. This assembly integrates directly into the transmission housing to convert engine power into smooth, variable-speed output for wheeled or tracked applications. As a fully sealed unit, it eliminates the need for a mechanical clutch in many configurations. The SKU 4143.020.222 is a direct OEM replacement, ensuring exact fitment and performance within the HL 100 and HL 270 series families. When servicing this drive, always inspect the surrounding 4143101043: HOUSING for cracks or wear, as misalignment can compromise the hydrostatic seal.
Symptoms of Failure
- Oil leaks around the drive shaft seal: Worn internal seals cause hydraulic fluid to weep from the input or output shafts, leading to low oil levels and erratic operation.
- Gear slipping under load: A failing hydrostatic unit cannot maintain pressure, resulting in intermittent power loss or “slipping” during acceleration or hill climbs.
- Excessive whining or grinding noise: Internal bearing wear or cavitation produces a high-pitched whine or metallic grinding sound, especially at low speeds.
- Erratic speed control: The drive may surge or fail to respond smoothly to throttle changes, indicating worn pistons or valve plate damage inside the assembly.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4143.020.222 |
| Assembly Type | 2 HL 250 Hydrostatic Drive (Complete Unit) |
| OEM Reference | ZF 2 HL 250 |
| Material | High-strength cast iron housing with hardened steel internals |
| Dry Weight | Approx. 18.5 kg (40.8 lbs) |
| Overall Dimensions | 320 mm x 220 mm x 180 mm |
| Max Operating Pressure | 250 bar (3,625 psi) |
| Seal Type | PTFE lip seals with O-ring backup |
Compatibility
This hydrostatic drive assembly is engineered for ZF WG180, WG200, and WG250 series transmissions, as well as earlier HL 100 and HL 270 models. It is commonly used in agricultural tractors, compact loaders, and industrial sweepers. The unit interfaces directly with the 4143301055: HOUSING and the 4143298040: CASE to form the main gearbox enclosure. Always verify your transmission’s serial number before ordering. For final assembly, the 0631329135: SPRING PIN must be installed to lock the drive shaft alignment.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4143101043 | HOUSING | Encloses the hydrostatic drive and supports bearings |
| 4143301055 | HOUSING | Secondary housing for valve plate and porting |
| 4143298040 | CASE | Main transmission case that houses the gear train |
| 0631329135 | SPRING PIN | Locks drive shaft to prevent axial movement |
| 0501214034 | SEALING CAP | Seals the hydrostatic unit’s fill port |
| 0636101024 | CAP SCREW | Secures the housing to the transmission case |
| 4475280099 | SCREW PLUG | Closes the pressure test port |
| 0634303266 | O-RING | Provides a hydraulic seal between mating surfaces |
| 4143301045 | SCREEN SHEET | Filters debris from the hydraulic fluid intake |
| 0636420051 | COUNTERSUNK SCREW | Fastens the screen sheet to the housing |
