Overview
The ZF 4644.026.380 6 WG 200 (555/5) Powershift Transmission Assembly is a complete, factory-matched unit designed for heavy-duty off-highway applications. This assembly integrates the main gear cluster, clutch packs, and hydraulic control components into a single, ready-to-install package. As a core element of the WG 200 series, it manages torque distribution across six forward and one reverse speed, ensuring smooth power delivery under extreme loads. The SKU 4644.026.380 is a direct OEM replacement for ZF powershift systems used in construction, mining, and agricultural machinery. When installing this unit, always pair it with a compatible TRANSMISSION HOUSING (4644101249) to maintain structural integrity, and verify the condition of the TRANSMISSION HOUSING (4644301402) for proper alignment of internal components.
Symptoms of Failure
- Delayed or harsh engagement: When the 4644.026.380 assembly wears, you may notice a pronounced lag between shifting and actual gear engagement, often accompanied by a jarring clunk. This indicates worn clutch discs or degraded hydraulic seals within the unit.
- Progressive oil leaks around the housing interface: A common failure point is the seal between the transmission assembly and its mating surfaces. Look for fluid weeping near the joint where the assembly meets the COVER PLATE (4644301298), often caused by a failing O-RING (0634306323).
- Intermittent power loss under load: As internal components fatigue, the transmission may slip during heavy pulling or climbing, causing a sudden drop in wheel speed without a corresponding engine RPM change. This symptom often precedes total clutch pack failure.
- Contaminated transmission fluid with metallic debris: Worn bearings or gear teeth within the assembly shed fine metal particles into the oil. If you observe glitter-like particles on the dipstick or during oil changes, the 4644.026.380 requires immediate replacement.
Technical Specifications
| Parameter | Specification |
|---|---|
| OEM Part Number | 4644.026.380 |
| Series | WG 200 (6 WG 200 555/5) |
| Assembly Type | Complete Powershift Transmission Unit |
| Dry Weight (approx.) | 185 kg (408 lbs) |
| Housing Material | High-Grade Cast Iron (GGG-40) |
| Overall Length | 720 mm |
| Overall Width | 480 mm |
| Overall Height | 510 mm |
| Input Torque Capacity | 555 Nm (peak) |
| Speed Configuration | 6 Forward / 1 Reverse |
| Sealing System | Integrated O-Ring & Gasket Set |
Compatibility
This 4644.026.380 assembly is specifically engineered for the ZF WG 200 series powershift transmissions. It is a direct fit for models including the WG180, WG200, and WG210 variants used in loaders, graders, and dump trucks. The unit also cross-references with certain WG 150 series applications when used with the correct adapter housing. For auxiliary sealing and filtration, consider the SCREW PLUG (0636305026) for drain ports, the SCREEN SHEET (4644301279) for oil intake protection, and the SEALING CAP (4644301088) for unused hydraulic ports. For a full overhaul, the REPAIR KIT (4644298503) contains all necessary gaskets and seals.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101249 | TRANSMISSION HOUSING | Main structural casing for gear train |
| 4644301402 | TRANSMISSION HOUSING | Secondary housing for clutch pack support |
| 4644301298 | COVER PLATE | Seals the rear access port of the assembly |
| 0634306323 | O-RING | Provides leak-proof seal between housings |
| 0636305026 | SCREW PLUG | Closes oil drain and fill ports |
| 4644301279 | SCREEN SHEET | Filters large debris from hydraulic oil |
| 4644301088 | SEALING CAP | Protects unused hydraulic connections |
| 4644298503 | REPAIR KIT | Contains all seals and gaskets for rebuild |
| 4475280079 | SCREW PLUG | Magnetic drain plug for ferrous debris |
| 4644121150 | OIL PIPE | Routes pressurized oil to clutch packs |
