Overview
The ZF 4644.120.006 PRESSURE REGULATOR is a precision hydraulic control component engineered specifically for the WG150 and WG180 series transmissions. This OEM genuine part governs the modulation of hydraulic pressure within the valve body assembly, ensuring consistent clutch engagement and smooth gear transitions. The SKU 4644.120.006 acts as a critical interface between the transmission control unit and the hydraulic circuit, maintaining optimal pressure thresholds during load shifts. When installed alongside a TRANSMISSION HOUSING (4642101047) or a TRANSMISSION HOUSING (4642301207), this regulator ensures the entire assembly operates within factory-specified tolerances.
Symptoms of Failure
- Erratic gear slipping under load: A worn 4644.120.006 often causes the transmission to slip between second and third gear, especially when climbing grades or carrying heavy payloads.
- Delayed or harsh engagement: You may notice a pronounced lag when shifting from neutral to drive, followed by a jarring engagement—a classic sign of pressure instability.
- Hydraulic fluid seepage near the valve body: Internal seal degradation in this pressure regulator can lead to oil weeping around the regulator bore, often mistaken for a housing leak.
- Inconsistent shift timing: The transmission may shift too early or too late, causing the engine to hunt for the correct gear ratio during acceleration.
Technical Specifications
| Specification | Value |
|---|---|
| Part Number (SKU) | 4644.120.006 |
| OEM Reference | ZF 4644 120 006 |
| Material | Hardened steel with nitrile sealing elements |
| Weight | 0.34 kg (0.75 lbs) |
| Overall Length | 68 mm |
| Outer Diameter | 22 mm |
| Operating Pressure Range | 8–16 bar |
| Thread Type | M12 x 1.5 |
Compatibility
This pressure regulator is a direct fit for ZF WG150 and WG180 series transmissions, commonly found in medium-duty trucks, buses, and construction equipment. It also serves as a service replacement for certain WG200 variants that share the same valve body architecture. When replacing this unit, always inspect the TYPE PLATE (0730365067) to confirm the exact transmission model, and verify that the GROOVED STUD (0631311009) securing the regulator housing is torqued to factory specifications.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4642101047 | TRANSMISSION HOUSING | Encloses the gear train and valve body assembly |
| 4642301207 | TRANSMISSION HOUSING | Alternate housing variant for WG180 series |
| 0730365067 | TYPE PLATE | Identification plate for transmission model verification |
| 0631311009 | GROOVED STUD | Secures pressure regulator and housing alignment |
| 4642301168 | SCREEN SHEET | Filters hydraulic fluid entering the valve body |
| 4642301169 | SCREEN SHEET | Secondary filtration layer for high-pressure circuits |
| 0636100621 | HEXAGON SCREW | Fastener for mounting the regulator bracket |
| 4642301186 | SCREEN SHEET | Fine-mesh screen for the return line |
| 4644106300 | SHIFT SYSTEM | Mechanical linkage for gear selection |
| 4644306500 | COVER PLATE | Seals the valve body access port |
