Overview
This genuine OEM ZF 4644.330.393 component is a critical internal actuator designed specifically for the WG 158 series transmission. It functions as a precision hydraulic control element, modulating oil flow to engage clutch packs and manage gear selection within the main gear train. The SKU 4644.330.393 sits directly within the valve body assembly, translating pilot pressure into mechanical movement. For optimal sealing and alignment, this part is often replaced alongside the TRANSMISSION HOUSING to prevent cross-threading and ensure proper bore geometry.
Symptoms of Failure
- Delayed or harsh engagement: When the 4644.330.393 wears, internal leakage causes a lag when shifting from Neutral to Drive or Reverse, often accompanied by a jarring clunk.
- Intermittent gear slipping under load: A failing actuator cannot maintain adequate line pressure, leading to clutch slip during uphill climbs or heavy hauling.
- Erratic shift timing: Worn internal seals cause the transmission to shift too early or too late, hunting for gears on level roads.
- Visible fluid contamination: Debris from a degraded 4644.330.393 can migrate into the SHIFT SYSTEM, causing valve sticking and erratic pressure regulation.
Technical Specifications
| Parameter | Value |
|---|---|
| OEM Part Number | 4644.330.393 |
| Material | Hardened steel body with nitrile seals |
| Weight | 0.85 kg (1.87 lbs) |
| Bore Diameter | 22.5 mm |
| Operating Pressure | 8–15 bar (116–218 psi) |
| OEM Reference | ZF WG158 |
Compatibility
This genuine ZF 4644.330.393 is engineered for the WG 158 series, but its design principles extend to other ZF WG-family transmissions. It is directly compatible with WG158, WG180, and WG200 models that share the same valve body architecture. For proper fitment, always verify the bore condition of the GEAR SHIFT HOUSING, as scoring in that component can accelerate wear on the new actuator. The part also interfaces with the SCREW-IN SLEEVE which retains the actuator in its bore.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101190 | TRANSMISSION HOUSING | Main structural casing that aligns all rotating assemblies |
| 4644159347 | SHIFT SYSTEM | Hydraulic valve network controlling clutch and band application |
| 4475280036 | SCREW-IN SLEEVE | Threaded retainer securing the actuator in its bore |
| 4644306511 | GEAR SHIFT HOUSING | Upper valve body cover with shift rail guides |
| 4644306440 | PISTON | Hydraulic piston converting oil pressure to linear motion |
| 0635470104 | ROLLER | Needle bearing reducing friction in shift linkage |
| 0730006344 | RING | Sealing ring for actuator bore (size A) |
| 0730006345 | RING | Sealing ring for actuator bore (size B) |
| 0730006346 | RING | Sealing ring for actuator bore (size C) |
| 0730006347 | RING | Sealing ring for actuator bore (size D) |
Frequently Asked Questions
Q: Can I replace the 4644.330.393 without removing the transmission?
A: Yes, in most WG158 applications, this actuator is accessible after removing the transmission oil pan and valve body. However, you must inspect the TRANSMISSION HOUSING bore for wear before installation.
Q: What causes premature failure of this part?
A: The most common cause is contaminated transmission fluid containing clutch debris. This abrades the sealing edges. Always replace the SHIFT SYSTEM filter simultaneously to prevent recurrence.
Q: Does this part require special tools for installation?
A: A seal protector sleeve is recommended to avoid damaging the O-rings when inserting the actuator into the GEAR SHIFT HOUSING. Torque the SCREW-IN SLEEVE to 35 Nm.
📞 Need this part? Contact our ZF specialists:
Email: info@partszf.com |
Phone: +86 158 2286 3467 |
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