Overview
The ZF 4644.303.556 SCREW-IN SLEEVE is a precision-machined hydraulic component engineered for the WG65 transmission series and its broader WG family. This sleeve functions as a critical fluid routing interface within the valve body assembly, directing pressurized oil to specific clutch packs and shift actuators. As an OEM genuine part (SKU: 4644.303.556), it ensures exact sealing tolerances and flow characteristics required for proper gear engagement. When installed, this screw-in sleeve mates directly against the TRANSMISSION HOUSING, forming a leak-proof junction that maintains system pressure during high-torque operations.
Symptoms of Failure
- External oil seepage around the valve body cover – A worn 4644.303.556 sleeve often causes gradual ATF leakage at the housing interface, leaving visible drips under the transmission pan.
- Erratic shift timing or delayed engagement – When the sleeve’s sealing surface degrades, hydraulic pressure drops, leading to soft shifts or hesitation when moving from Neutral to Drive.
- Persistent low transmission fluid warning – Internal leakage past the screw-in sleeve can slowly deplete fluid levels without external puddles, triggering dashboard alerts.
- Whining noise during gear changes – Air entrainment from a compromised sleeve seal creates a high-pitched whine, particularly under load in WG65 and WG180 series transmissions.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4644.303.556 |
| Type | Screw-in Sleeve (Hydraulic) |
| Material | Hardened Steel with Nitrile Coating |
| Thread Size | M22 x 1.5 |
| Overall Length | 38 mm |
| Hex Drive Size | 17 mm |
| Weight | 0.045 kg |
| OEM Reference | ZF 4644.303.556 |
| Sealing Torque | 25 Nm |
Compatibility
This screw-in sleeve is designed for ZF’s WG series powershift transmissions. Verified compatibility includes the following models: WG65 Series, WG 100 Series, WG 150 Series, WG 180 Series, WG 181 Series, WG 200 Series, WG 201 Series, and WG 250 Series. It is a direct replacement for the original factory-installed sleeve in these units. During installation, always pair this sleeve with new sealing hardware such as the O-RING (0634313118) and verify the HEXAGON SCREW (0636011038) torque specifications. For complete assembly, the HEXAGON SCREW (0636011118) and HEXAGON SCREW (0636016015) are also required to secure the valve body cover.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4616101059 | TRANSMISSION HOUSING | Main structural casing for gear train |
| 0636011038 | HEXAGON SCREW | Fastener for valve body cover |
| 0636011118 | HEXAGON SCREW | Fastener for oil pan |
| 0636016015 | HEXAGON SCREW | Fastener for clutch housing |
| 0631306085 | CYLINDRICAL PIN | Alignment dowel for valve body |
| 0634313118 | O-RING | Seal for sleeve bore |
| 0636304019 | SCREW PLUG | Closes unused hydraulic ports |
| 0634801152 | SEALING RING | Copper washer for drain plug |
| 0732611049 | FILTER INSERT | Internal hydraulic fluid filter |
| 0634303718 | O-RING | Seal for filter housing |
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