Overview
The ZF 4644.120.021 PRESSURE REGULATOR is a critical hydraulic control component engineered for the WG180 and WG200 series transmissions. This OEM genuine part precisely modulates oil pressure within the valve body assembly, ensuring consistent clutch engagement and smooth gear shifts under heavy load. The SKU 4644.120.021 acts as a direct replacement for worn units, restoring the transmission’s ability to maintain stable line pressure. When installed alongside the 4644105475 DISCONNECTION and the 4644101134 TRANSMISSION HOUSING, this regulator forms the backbone of the hydraulic circuit, preventing pressure spikes that can damage internal seals.
Symptoms of Failure
- Erratic shift timing and gear slipping – A failing 4644.120.021 pressure regulator causes inconsistent line pressure, leading to delayed upshifts or unexpected downshifts during acceleration.
- Oil leaks near the valve body – Worn internal O-rings or a cracked regulator bore allow transmission fluid to escape, often pooling around the 4642303097 OUTPUT FLANGE area.
- Harsh engagement from neutral to drive – When the regulator cannot dampen initial pressure surges, drivers experience jarring shifts that stress the 0636020211 HEXAGON SCREW fasteners and surrounding housing.
- Overheating transmission fluid – Continuous pressure fluctuations generate excessive heat, accelerating fluid degradation and reducing overall transmission life.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4644.120.021 |
| Material | Hardened steel with zinc-nickel coating |
| Weight | 0.45 kg (1.0 lb) |
| Operating Pressure Range | 8–22 bar (116–319 psi) |
| OEM Reference | ZF 4644.120.021 |
| Seal Type | Integrated PTFE backup ring |
Compatibility
This pressure regulator is specifically designed for ZF WG180 and WG200 series transmissions used in heavy-duty construction and agricultural machinery. It directly replaces the original factory-installed unit in models such as WG180-1, WG180-2, WG200-1, and WG200-2. Always verify the valve body casting number before installation. The regulator works in concert with the 4644301349 HOUSING and requires proper torque on the 0636305019 SCREW PLUG to prevent fluid bypass.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644105475 | DISCONNECTION | Isolates transmission from driveline during service |
| 4642303097 | OUTPUT FLANGE | Transfers torque to driveshaft |
| 0636020211 | HEXAGON SCREW | Secures valve body components |
| 4644101134 | TRANSMISSION HOUSING | Encloses gear train and hydraulic circuits |
| 4644301349 | HOUSING | Supports valve body assembly |
| 0730365125 | TYPE PLATE | Identifies transmission model and serial number |
| 0631311009 | GROOVED STUD | Provides alignment for housing mounting |
| 0636305019 | SCREW PLUG | Seals pressure test ports |
| 4644301247 | THREADED BUSH | Reinforces threaded connections in housing |
| 0634303485 | O-RING | Prevents fluid leaks at mating surfaces |
