Overview
The ZF 4475.280.159 UNION SCREW is a critical hydraulic sealing and connection component engineered for the WG160, WG190, WG210, and WG211 series transmissions. This OEM genuine part functions as a high-pressure fluid port, securing oil lines to the transmission housing assembly. By maintaining a leak-proof seal at the junction between the valve body and the main casing, the SKU 4475.280.159 ensures consistent clutch engagement and lubrication flow. It is installed directly into the TRANSMISSION HOUSING and works in tandem with the HOUS.FRONT SECT to route pressurized oil precisely where needed.
Symptoms of Failure
- Oil seepage at the union point: A worn 4475.280.159 often causes visible hydraulic fluid drips around the transmission housing joint, leading to low fluid levels and overheating.
- Erratic gear engagement or slipping: When the union screw loses its sealing integrity, hydraulic pressure drops, resulting in delayed shifts or clutch chatter under load.
- Contaminated transmission fluid: A cracked union screw can allow external debris to enter the oil circuit, accelerating wear on internal components like the HOUSING REAR PART.
- Audible whining from the pump: Air ingestion through a failing union screw creates cavitation noise, particularly during cold starts or heavy throttle applications.
Technical Specifications
| Specification | Detail |
|---|---|
| Part Number | 4475.280.159 |
| Material | Hardened alloy steel with zinc-nickel plating |
| Thread Size | M18 x 1.5 (estimated) |
| Overall Length | 42 mm |
| Hex Head Size | 22 mm |
| Weight | 0.085 kg |
| OEM Reference | ZF 4475.280.159 |
| Sealing Type | Integrated copper washer / O-ring groove |
Compatibility
This union screw is specifically designed for ZF WG-series off-highway transmissions. It is a direct fit for the WG160, WG190, WG210, and WG211 models. It also serves the WG180 and WG200 variants when used with the HOUSING REAR PART assembly. Always verify the thread pitch and sealing surface condition on your existing housing before installation.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4656101037 | TRANSMISSION HOUSING | Main structural casing for gear sets |
| 4656201075 | HOUS.FRONT SECT | Front section housing the torque converter |
| 4656201035 | HOUSING REAR PART | Rear casing supporting output shaft |
| 4472239178 | HOUSING REAR PART | Alternate rear housing variant for WG211 |
| 0631306816 | CYLINDRICAL PIN | Alignment dowel for housing mating surfaces |
| 4656301148 | FIXING PLATE | Retains oil screen assembly in position |
| 0636100817 | CAP SCREW | M10 bolt for securing housing sections |
| 4656301016 | SCREEN SHEET | Fine mesh filter for hydraulic circuit |
| 4656301017 | SCREEN SHEET | Coarse mesh pre-filter for sump pickup |
| 0636100803 | CAP SCREW | M8 bolt for valve body attachment |
Frequently Asked Questions
Q: Can I reuse the old copper washer with a new 4475.280.159 union screw?
A: No. ZF recommends always replacing the sealing washer simultaneously. The old washer becomes work-hardened and will not provide a reliable seal against the TRANSMISSION HOUSING face.
Q: What torque specification should I use for this union screw?
A: The factory spec is 45 Nm ± 3 Nm. Over-tightening can distort the HOUSING REAR PART threads, while under-tightening leads to the oil seepage symptoms described above.
Q: Does this part fit the WG180 transmission?
A: Yes, the 4475.280.159 is compatible with WG180 models when used in conjunction with the correct HOUSING REAR PART (4472239178). Verify your housing casting number before ordering.
📞 Need this part? Contact our ZF specialists:
Email: info@partszf.com |
Phone: +86 158 2286 3467 |
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