Overview
The ZF 4644.026.351 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 within the WG 200 Series, it manages torque distribution across six forward speeds and one reverse, ensuring smooth, uninterrupted shifts under extreme loads. The SKU 4644.026.351 identifies this specific build variant, which includes the 555/5 ratio set optimized for high-torque diesel engines. When replacing this unit, it is critical to inspect the surrounding structural components, such as the 4644101249: TRANSMISSION HOUSING, to ensure proper alignment and sealing of the new assembly.
Symptoms of Failure
- Delayed or harsh gear engagement: When the assembly wears, internal clutch clearance increases, causing a noticeable lag or a violent “clunk” when shifting from neutral to drive or between ranges.
- Progressive oil leaks at the bell housing: Deterioration of internal seals within the 4644.026.351 allows transmission fluid to weep past the input shaft, often pooling at the bottom of the 4644301402: TRANSMISSION HOUSING.
- Torque converter lock-up shudder: Worn friction discs inside the powershift unit cause a vibration or shudder during converter lock-up, particularly under load on inclines.
- Loss of forward or reverse drive: Complete hydraulic pressure loss due to internal seal failure in the assembly results in a total inability to move the vehicle, even with the engine at full RPM.
Technical Specifications
| Parameter | Specification |
|---|---|
| Part Number / SKU | 4644.026.351 |
| Assembly Type | Complete Powershift (6 WG 200) |
| Dry Weight (approx.) | 185 kg (408 lbs) |
| Input Torque Rating | 555 Nm (409 lb-ft) |
| Number of Speeds | 6 Forward / 1 Reverse |
| Primary Material | High-strength cast iron housing with hardened steel gears |
| OEM Reference | ZF 6 WG 200 (555/5) |
| Sealing System | Requires 0634306323: O-RING for input cover |
| Output Interface | Compatible with 4644309001: OUTPUT FLANGE |
Compatibility
This complete assembly is engineered for the ZF WG 200 Series transmission family. It is directly compatible with models including the WG180, WG200, and WG210, where the 555/5 gear ratio set is specified. The unit also fits select variants of the WG 190 and WG 220 when used with the correct 4644301298: COVER PLATE to adapt the hydraulic control bore pattern. Always verify the bell housing bolt pattern against your existing 4644101249: TRANSMISSION HOUSING before installation. For machines originally equipped with a WG 180, a full compatibility check of the output shaft spline count is required.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101249 | TRANSMISSION HOUSING | Main structural casing for the gear train |
| 4644301402 | TRANSMISSION HOUSING | Alternate housing variant for specific bell housing depths |
| 4644301298 | COVER PLATE | Seals the hydraulic control valve cavity |
| 0634306323 | O-RING | Critical seal between cover plate and housing |
| 0636305026 | SCREW PLUG | Seals oil drain and pressure test ports |
| 4644301279 | SCREEN SHEET | Fine mesh filter for hydraulic oil return circuit |
| 4644301088 | SEALING CAP | Protects exposed splines during transport |
| 4644298503 | REPAIR KIT | Contains all gaskets and seals for overhaul |
| 4644309001 | OUTPUT FLANGE | Connects transmission to driveshaft |
| 4475280079 | SCREW PLUG | Magnetic drain plug for ferrous debris capture |
