Overview
The ZF 4644.306.581 ORIFICE is a precision-machined hydraulic flow control component engineered specifically for the WG 65 Series transmission. This OEM genuine part regulates oil pressure and volume within the valve body assembly, ensuring precise clutch and brake application timing. Located within the hydraulic control circuit, the orifice restricts fluid flow to maintain consistent shift quality and prevent pressure spikes. The SKU 4644.306.581 is a direct replacement for the original factory-installed component, guaranteeing exact dimensional tolerances and material composition. When paired with the 4616105413: OUTPUT and 4616203017: OUTPUT FLANGE, this orifice ensures seamless hydraulic communication throughout the drivetrain.
Symptoms of Failure
- Delayed or harsh gear engagement: A worn or clogged orifice disrupts oil flow, causing noticeable lag when shifting from neutral to drive or reverse.
- Intermittent transmission slipping under load: Inconsistent hydraulic pressure leads to clutch pack slippage, particularly during uphill climbs or heavy hauling.
- Oil leaks around the valve body area: Degraded sealing surfaces on the orifice can allow ATF to weep, leaving visible drips under the transmission pan.
- Erratic shift timing: The transmission may shift too early or too late, often accompanied by a sudden flare in RPM between gears.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4644.306.581 |
| OEM Reference | ZF 4644.306.581 |
| Material | Hardened steel with corrosion-resistant coating |
| Orifice Diameter | 2.5 mm (0.098 in) |
| Overall Length | 18.0 mm (0.709 in) |
| Thread Size | M10 x 1.0 |
| Weight | 12 g (0.42 oz) |
| Sealing Type | Integrated O-ring groove |
Compatibility
This orifice is primarily designed for the ZF WG 65 Series transmission, but it also fits several other ZF models that share the same hydraulic control architecture. Compatible transmissions include the WG65, WG80, WG120, WG150, WG180, and WG200 series. It is commonly used in medium-duty trucks, buses, and off-highway equipment. For proper installation, ensure the 4616101117: TRANSMISSION HOUSING is clean and free of debris, and secure the assembly with the 0636011038: HEXAGON SCREW to prevent vibration loosening.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4616105413 | OUTPUT | Transfers torque from transmission to driveshaft |
| 4616203017 | OUTPUT FLANGE | Connects output shaft to universal joint |
| 4616101117 | TRANSMISSION HOUSING | Encloses internal gear and clutch assemblies |
| 0636011038 | HEXAGON SCREW | Secures housing and valve body components |
| 0636016015 | HEXAGON SCREW | Fastens output flange to shaft |
| 0631306085 | CYLINDRICAL PIN | Aligns valve body and housing during assembly |
| 0634313118 | O-RING | Seals hydraulic passages between components |
| 0732611049 | FILTER INSERT | Traps contaminants in transmission fluid |
| 0634303718 | O-RING | Prevents fluid bypass at orifice seat |
| 0636610082 | STUD | Provides threaded mounting point for accessories |
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