Overview
The ZF 4644.306.599 REDUCTION VALVE is a critical hydraulic control component engineered for the WG 65, WG 100, and WG 150 series transmissions. This OEM genuine part precisely modulates pilot pressure to the main regulator valve, ensuring smooth clutch engagement and consistent line pressure during gear shifts. As a pressure-reducing element, it sits within the valve body assembly, directly interfacing with the TRANSMISSION HOUSING to maintain hydraulic stability. The SKU 4644.306.599 is factory-calibrated to ZF specifications, making it essential for maintaining original shift feel and preventing premature wear on internal components.
Symptoms of Failure
- Erratic or delayed shifting – A worn reduction valve causes inconsistent pilot pressure, leading to harsh or delayed gear engagement, especially under load.
- Transmission oil leaks – Deteriorated sealing surfaces on the valve body allow ATF to bypass, resulting in visible drips near the valve cover or cooler lines.
- Low line pressure warnings – When the valve fails to reduce pressure correctly, the transmission control module may trigger fault codes for insufficient main pressure, often accompanied by slipping in higher gears.
- Overheating during operation – Continuous pressure loss forces the pump to work harder, generating excess heat that can degrade fluid and damage clutches.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4644.306.599 |
| OEM Reference | ZF 4644.306.599 |
| Material | Hardened steel with zinc-nickel plating |
| Weight | 0.18 kg (0.40 lbs) |
| Length | 62 mm |
| Diameter | 18 mm |
| Seal Type | Integrated O-ring groove (uses O-RING 0634313118) |
| Thread Size | M10 x 1.0 (mounting) |
Compatibility
This reduction valve is a direct fit for the ZF WG65 series and its derivatives, including the WG100 and WG150 models. It is also compatible with the WG180 and WG200 transmissions when used in conjunction with the correct HOUSING 4616301307 or HOUSING 4616301309. For proper installation, ensure the valve bore is clean and the mating HEXAGON SCREW 0636011118 is torqued to 25 Nm. Always replace the sealing ring and O-ring simultaneously to prevent cross-threading.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4616101066 | TRANSMISSION HOUSING | Main structural casing for valve body and gear sets |
| 0636011118 | HEXAGON SCREW | Fastener for valve body retention |
| 4616301307 | HOUSING | Intermediate housing for WG100/150 valve assemblies |
| 4616301309 | HOUSING | Alternate housing for WG180/200 valve assemblies |
| 0636011038 | HEXAGON SCREW | M8 fastener for cover plate |
| 0636016015 | HEXAGON SCREW | M12 fastener for pump mounting |
| 0631306085 | CYLINDRICAL PIN | Alignment dowel for valve body positioning |
| 0634313118 | O-RING | Seal for valve bore interface |
| 0636304019 | SCREW PLUG | Port plug for pressure test points |
| 0634801152 | SEALING RING | Copper washer for banjo bolt sealing |
Authorized ZF Distributor
We are a certified supplier of genuine ZF components.
