Overview
The ZF 4644.026.390 6 WG 200 Powershift Transmission Assembly is a complete, factory-matched unit designed for heavy-duty off-highway applications. This assembly integrates the main gear train, clutch packs, and hydraulic control system into a single, ready-to-install package. As the core of the WG 200 series, it manages torque distribution across six forward speeds and one reverse, ensuring smooth power delivery under extreme loads. The SKU 4644.026.390 is a direct replacement for OEM units, eliminating the need for partial rebuilds. When installing this assembly, always inspect the TRANSMISSION HOUSING (part 4644101275) for cracks, as the housing provides the structural foundation for the entire unit. Additionally, verify the condition of the TRANSMISSION HOUSING (4644301406) which supports the output shaft bearing cluster.
Symptoms of Failure
- Delayed or harsh gear engagement: When the assembly’s internal clutch seals degrade, you will notice a pronounced lag or jarring shift between forward and reverse, especially under load.
- Erratic shift patterns and gear slipping: Worn valve body components within the 4644.026.390 cause the transmission to hunt for gears or slip out of gear on inclines, a common issue in WG200 units.
- External oil leaks at the bell housing: Cracks in the main casing or failed gaskets lead to ATF pooling near the flywheel, often misdiagnosed as a rear main seal failure.
- Overheating during low-speed operation: Internal debris from a failing assembly restricts oil flow, causing the transmission to exceed normal operating temperatures in under 30 minutes of use.
Technical Specifications
| Parameter | Specification |
|---|---|
| OEM Part Number | 4644.026.390 |
| Series | WG 200 (6 WG 200) |
| Dry Weight | Approx. 185 kg (408 lbs) |
| Overall Length | 720 mm |
| Overall Width | 480 mm |
| Overall Height | 510 mm |
| Housing Material | High-strength cast iron (GGG-40) |
| Input Torque Capacity | 2,000 Nm (1,475 lb-ft) |
| Number of Speeds | 6 Forward / 1 Reverse |
| Fluid Capacity | 28 liters (7.4 gallons) |
Compatibility
This 4644.026.390 assembly is engineered for the ZF WG 200 series, specifically the 6 WG 200 variant. It is directly compatible with WG 180 and WG 200 models that share the same bell housing pattern and input spline count. The unit also fits select WG 160 applications when paired with the correct TYPE PLATE (0730301612) for identification. For installations requiring a sealed sump, the COVER PLATE (4644301298) must be used to prevent contamination. Always cross-reference your vehicle’s serial number with ZF documentation to confirm fitment for WG200, WG180, and WG160 chassis.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101275 | TRANSMISSION HOUSING | Main structural casing for gear train |
| 4644301406 | TRANSMISSION HOUSING | Output shaft support housing |
| 0730301612 | TYPE PLATE | Identification and serial number plate |
| 4644301298 | COVER PLATE | Seals the PTO access port |
| 0634306323 | O-RING | Seals housing joints against leaks |
| 0636305026 | SCREW PLUG | Closes oil drain/fill ports |
| 4644301279 | SCREEN SHEET | Filters debris from hydraulic fluid |
| 4644301088 | SEALING CAP | Protects unused hydraulic ports |
| 4644106328 | SHIFT SYSTEM | Electro-hydraulic valve body assembly |
| 4644109045 | PARKING BRAKE | Spring-applied, hydraulically released brake |
