Overview
The ZF 0631.402.004 SLOTTED PLUG is a critical sealing and access component engineered for the WG65 series of heavy-duty transmissions. This OEM genuine part functions as a threaded closure within the transmission housing, providing a secure seal for hydraulic or lubrication passages while allowing for diagnostic access or fluid evacuation. The slotted design facilitates easy removal and reinstallation using a standard screwdriver or impact driver. The SKU 0631.402.004 is precision-machined to ZF’s exacting tolerances, ensuring a leak-proof interface that maintains system pressure and prevents contamination ingress. It is typically located on the lower or side pan of the TRANSMISSION HOUSING, directly adjacent to the OUTPUT assembly.
Symptoms of Failure
When the 0631.402.004 SLOTTED PLUG degrades or is improperly torqued, operators will notice distinct performance issues. Look for these specific failure symptoms:
- External oil seepage from the transmission pan: A worn or cross-threaded plug allows transmission fluid to weep past the threads, leaving visible drips under the vehicle near the OUTPUT FLANGE area.
- Contaminated transmission fluid: A compromised seal permits dirt and moisture to enter the sump, leading to premature wear of internal components like the OUTPUT shaft bearings.
- Intermittent low fluid pressure warnings: Air ingestion through a loose plug can cause aeration of the hydraulic fluid, resulting in erratic shift quality and gear slippage under load.
- Stripped slot or rounded head: Repeated removal with improper tools can deform the slotted drive, making future service of the TRANSMISSION HOUSING extremely difficult.
Technical Specifications
| Specification | Detail |
|---|---|
| Part Number (SKU) | 0631.402.004 |
| Product Type | Slotted Plug (Drain/Fill Port) |
| Material | Steel, Zinc-Plated (Corrosion Resistant) |
| Thread Size | M22 x 1.5 (Estimated) |
| Overall Length | 18 mm |
| Drive Type | Slotted (Flathead) |
| Weight | 0.04 kg (0.09 lbs) |
| OEM Reference | ZF 0631.402.004 |
| Sealing Method | Thread Sealant or Copper Washer (Sold Separately) |
Compatibility
This genuine ZF slotted plug is primarily designed for the WG65 series transmissions. However, due to its standardized thread pitch and sealing profile, it is also compatible with the following ZF models that share the same housing architecture: WG180, WG200, WG210, and WG250. It is commonly used in off-highway vehicles, construction equipment, and heavy-duty trucks. Always verify the thread size against your existing HEXAGON SCREW ports before installation.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4616105402 | OUTPUT | Transfers torque from transmission to driveshaft |
| 4005303005 | OUTPUT FLANGE | Connects output shaft to driveline yoke |
| 4616101119 | TRANSMISSION HOUSING | Main structural casing containing gear sets |
| 0636011038 | HEXAGON SCREW | Fastens housing covers and flanges |
| 0636011118 | HEXAGON SCREW | Secures valve body and filter assemblies |
| 0636016015 | HEXAGON SCREW | Mounts clutch pack retainers |
| 0631306085 | CYLINDRICAL PIN | Aligns housing halves during assembly |
| 0634313118 | O-RING | Seals hydraulic passages between components |
| 0636304019 | SCREW PLUG | Closes secondary access ports in the housing |
| 0634801152 | SEALING RING | Provides leak-proof seal under the plug head |
Authorized ZF Distributor
We are a certified supplier of genuine ZF components.
