Overview
The ZF 1402.321.050 UNION SCREW is a precision-engineered hydraulic connector designed for the WG 65 Series transmission. This OEM genuine part serves as a critical junction point within the transmission’s oil circulation system, ensuring secure fluid transfer between the valve body and cooler lines. The SKU 1402.321.050 is specifically machined to maintain proper sealing pressure in high-vibration environments, preventing contamination ingress. When installed alongside the TRANSMISSION HOUSING, this union screw guarantees uninterrupted lubrication to planetary gear sets and clutch packs.
Symptoms of Failure
- Hydraulic fluid seepage at the union screw connection: Visible oil droplets or wet spots around the WG65 transmission housing indicate degraded sealing surfaces, often accompanied by a burnt smell from fluid loss.
- Erratic gear engagement under load: A worn 1402.321.050 union screw reduces line pressure, causing delayed shifts or harsh engagement when towing or climbing grades.
- Transmission overheating warnings: Compromised fluid flow from a damaged union screw leads to inadequate cooling, triggering dashboard temperature alerts within 15-20 minutes of operation.
- Low fluid level without external leaks: Internal weeping past the union screw threads allows oil to bypass into the bell housing, masking the leak until the transmission pan is removed.
Technical Specifications
| Parameter | Specification |
|---|---|
| Part Number | 1402.321.050 |
| Material | Case-hardened steel (DIN 1.7131) |
| Thread Size | M18 x 1.5 (metric fine) |
| Overall Length | 42.5 mm |
| Hex Flats | 22 mm (AF) |
| Sealing Surface | 24° cone with O-ring groove |
| Weight | 0.085 kg |
| OEM Reference | ZF 1402.321.050 |
| Torque Spec | 45 Nm + 90° angle |
Compatibility
This union screw is validated for the ZF WG65 series and shares hydraulic circuit architecture with the WG180 and WG200 models. It directly interfaces with the OUTPUT FLANGE oil feed passages and secures the OUTPUT shaft lubrication line. The 1402.321.050 also fits WG120 and WG150 transmissions when used with the correct HEXAGON SCREW adapter kit. Always verify thread pitch compatibility with your specific housing casting number before installation.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4616105413 | OUTPUT | Transfers torque to driveshaft |
| 4616203017 | OUTPUT FLANGE | Connects output shaft to yoke |
| 4616101117 | TRANSMISSION HOUSING | Main structural casing |
| 0636011038 | HEXAGON SCREW | Fastens valve body cover |
| 0636016015 | HEXAGON SCREW | Secures oil pan |
| 0631306085 | CYLINDRICAL PIN | Aligns clutch drum assembly |
| 0634313118 | O-RING | Seals union screw connection |
| 0732611049 | FILTER INSERT | Traps debris in oil circuit |
| 0634303718 | O-RING | Seals output flange bore |
| 0636610082 | STUD | Positions cooler line bracket |
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