Overview
The ZF 4644.004.220 4 WG 180(500) Powershift Transmission Assembly is a complete, factory-matched unit designed for heavy-duty off-highway machinery. This assembly integrates the torque converter, planetary gear sets, and clutch packs into a single, ready-to-install module. As the core of the driveline, it manages power distribution from the engine to the axles under high-load conditions. The SKU 4644.004.220 is a direct OEM replacement for the WG 180 series, ensuring precise fitment and original performance characteristics. When installing this unit, it is critical to verify the integrity of the TRANSMISSION HOUSING and the HOUSING to prevent misalignment.
Symptoms of Failure
- Delayed or harsh gear engagement: When the assembly wears, you may experience a noticeable lag between shifting and actual gear engagement, often accompanied by a jarring clunk. This is a common sign of internal clutch pack wear.
- Transmission overheating under load: A failing unit will generate excessive heat due to internal friction, leading to fluid breakdown and potential thermal damage to the O-RING seals.
- Oil leaks near the bell housing or output flange: Worn seals or a cracked THREADED BUSH can allow pressurized fluid to escape, leaving puddles under the vehicle.
- Intermittent power loss or slipping: The transmission may momentarily lose torque under acceleration, indicating worn clutches or a failing torque converter stator.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4644.004.220 |
| Assembly Type | 4 WG 180(500) Powershift |
| Dry Weight (approx.) | 285 kg (628 lbs) |
| Overall Length | 720 mm |
| Housing Material | Cast Iron (GGG-40) |
| OEM Reference | ZF 4644.004.220 |
| Max Input Torque | 500 Nm |
| Fluid Capacity | 12.5 Liters |
Compatibility
This complete unit is engineered for the ZF WG 180 series, specifically the 4 WG 180(500) variant. It is also mechanically compatible with the WG 200 series when used with the correct ADAPTER kit. The assembly fits popular models in the 4WG-180 family, including the 4 WG 180(400) and 4 WG 180(600), though the torque converter stall ratio may vary. Always cross-reference the TYPE PLATE on your existing unit to confirm exact compatibility. For secure mounting, the GROOVED STUD must be torqued to factory specifications.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101137 | TRANSMISSION HOUSING | Main structural casing for gear train |
| 4644301333 | HOUSING | Secondary housing for clutch pack assembly |
| 0730365125 | TYPE PLATE | Identification tag with serial number |
| 0631311009 | GROOVED STUD | Fastener for housing alignment |
| 0636305019 | SCREW PLUG | Seals fluid passages |
| 4644301247 | THREADED BUSH | Wear-resistant insert for pivot points |
| 0634303485 | O-RING | Hydraulic seal for valve body |
| 4644301257 | ADAPTER | Interface for alternate bell housings |
| 0634306023 | O-RING | Seal for output shaft cover |
| 4644106231 | SHIFT SYSTEM | Electro-hydraulic shift control module |
