Overview
The ZF 4644.026.375 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 elements into a single, ready-to-install package. As the core power transfer module in the WG 200 series, it manages torque distribution across six forward speeds and one reverse, ensuring smooth directional changes under load. The SKU 4644.026.375 is a direct OEM replacement assembly, eliminating the need for piecemeal rebuilding. It works in concert with the 4644101249: TRANSMISSION HOUSING to form the structural backbone of the gearbox, while the 4644301402: TRANSMISSION HOUSING provides the opposite-end sealing and bearing support. This assembly is precision-balanced and pressure-tested to meet ZF’s original factory specifications.
Symptoms of Failure
When the ZF 4644.026.375 assembly begins to degrade, operators typically notice three distinct failure modes. Erratic clutch engagement during power shifts is the most common complaint, often accompanied by a delayed or harsh “clunk” when changing direction. Hydraulic oil overheating above 120°C occurs when internal seal rings wear, allowing pressurized fluid to bypass the clutch pistons. A third indicator is progressive gear slippage under load, particularly in higher ranges, which points to worn friction discs within the assembly. Finally, metallic debris in the transmission oil filter signals advanced wear of the planetary gear sets or bearing races inside the 4644.026.375 unit. Addressing these symptoms early prevents collateral damage to the 4644301298: COVER PLATE and the 0634306323: O-RING sealing interfaces.
Technical Specifications
| Parameter | Specification |
|---|---|
| Assembly Type | Complete Powershift Transmission Unit |
| ZF Series | WG 200 (6 WG 200 variant) |
| Gear Configuration | 6 Forward / 1 Reverse (555/5 ratio set) |
| Dry Weight | Approx. 185 kg (408 lbs) |
| Housing Material | High-strength cast iron (GGG-40) |
| Input Torque Capacity | 550 Nm (405 ft-lbs) max |
| OEM Reference | 4644.026.375 (ZF Parts System) |
| Seal Kit Compatibility | Includes 0634306323: O-RING and gasket set |
Compatibility
This assembly is engineered specifically for the ZF WG 200 series of powershift transmissions, including the WG180, WG200, and WG210 variants used in wheel loaders, telehandlers, and industrial tractors. It directly replaces the 6 WG 200(555/5) configuration found in models such as the ZF 4WG-200 and 6WG-200. The unit is not compatible with the older WG 150 series or the electronic-controlled WG 310 series without adapter modifications. For correct installation, ensure your transmission housing matches the 4644101249: TRANSMISSION HOUSING or the 4644301402: TRANSMISSION HOUSING depending on your specific application. Always verify the clutch pack count and valve body orientation before ordering.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101249 | TRANSMISSION HOUSING | Main structural casing for gear and shaft support |
| 4644301402 | TRANSMISSION HOUSING | Opposite-end housing with bearing journals |
| 4644301298 | COVER PLATE | Seals the clutch access port on the assembly |
| 0634306323 | O-RING | Hydraulic seal between housing and cover plate |
| 0636305026 | SCREW PLUG | Oil drain/fill port sealing plug |
| 4644301279 | SCREEN SHEET | Fine mesh filter for hydraulic circuit protection |
| 4644301088 | SEALING CAP | Protects exposed splines during transport |
| 4644109044 | PARKING BRAKE | Spring-applied, hydraulically released brake unit |
| 0501211070 | BRAKE | Service brake disc pack for wheel-end braking |
| 0501317036 | PISTON | Hydraulic actuation piston for clutch pack |
