Overview
The ZF 4475.280.055 SCREW PLUG is a critical sealing component designed for the oil circuits and housing cavities of the WG100, WG130, and WG131 series transmissions. This OEM genuine part ensures a leak-proof seal at threaded access points, preventing fluid loss and contamination ingress. The SKU 4475.280.055 is engineered to withstand high hydraulic pressures and thermal cycling typical in heavy-duty automatic transmissions. It is commonly installed directly into the 2095101022: TRANSMISSION HOUSING or the 2095301025: TRANSMISSION HOUSING, where it secures fluid passages and inspection ports.
Symptoms of Failure
- Transmission fluid seepage at housing ports: A worn or stripped 4475.280.055 screw plug often results in slow oil weeping around the threaded boss, leading to low fluid levels over time.
- Contaminated transmission fluid: When the seal integrity fails, dirt and moisture can enter through the plug interface, causing premature wear on internal clutches and bearings.
- Audible air ingestion or whining noise: A loose or cracked screw plug can allow air to enter the hydraulic circuit, producing a high-pitched whine during gear engagement or under load.
- Intermittent pressure loss in the valve body: Failure of this plug can cause erratic shift quality, as the hydraulic system cannot maintain consistent pressure for clutch application.
Technical Specifications
| Parameter | Value |
|---|---|
| OEM Part Number | 4475.280.055 |
| Thread Size | M18 x 1.5 (estimated) |
| Overall Length | 22 mm |
| Head Type | Hexagon socket (Allen) |
| Material | Steel, zinc-plated |
| Weight | 0.035 kg |
| Sealing Method | Copper washer or O-ring (use 0634304731: O-RING) |
| Torque Specification | 35 Nm (dry) |
Compatibility
This screw plug is factory-specified for the ZF WG100, WG130, and WG131 series transmissions. It is also commonly used as a replacement in the WG180 and WG200 models where the same M18 port is present on the 2095101022: TRANSMISSION HOUSING or the 2095301025: TRANSMISSION HOUSING. For applications requiring a different thread configuration, consider the 4475280150: SCREW PLUG which fits alternate housing ports. Always verify the thread pitch against your housing bore before installation.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 2095101022 | TRANSMISSION HOUSING | Main structural casing for gear sets |
| 2095301025 | TRANSMISSION HOUSING | Alternate housing variant for WG series |
| 4475280150 | SCREW PLUG | Alternate thread size plug for different ports |
| 0634304731 | O-RING | Sealing ring for screw plug interface |
| 0636011207 | HEXAGON SCREW | Fastener for housing cover plates |
| 0636011188 | HEXAGON SCREW | Fastener for valve body retention |
| 0730365280 | TYPE PLATE | Identification plate for transmission model |
| 0501337897 | SPEED SENSOR | Monitors output shaft rotational speed |
| 0636101027 | CAP SCREW | Secures oil pan or filter cover |
| 0631306155 | CYLINDRICAL PIN | Alignment dowel for housing assembly |
