Overview
The ZF 4644.026.391 6 WG 200 Powershift Transmission Assembly is a complete, factory-engineered unit designed for heavy-duty off-highway machinery. This assembly serves as the central power distribution hub, converting engine torque into controlled hydraulic and mechanical output for wheel loaders, graders, and industrial vehicles. The SKU 4644.026.391 integrates the main gear set, clutch packs, and valve body into a single drop-in replacement, eliminating the need for piecemeal repairs. It mounts directly between the engine bellhousing and the final drive, ensuring seamless power flow under extreme load cycles.
Symptoms of Failure
- Erratic gear engagement or slipping under load: When the internal clutch packs or seals degrade, the transmission may hesitate or fail to hold gear, especially during uphill travel or heavy bucket loads.
- Hydraulic oil leaks from the housing seam: Worn gaskets or cracked castings around the main body can cause visible fluid loss, often detected as drips near the bellhousing or under the oil pan.
- Delayed or harsh shifting between forward and reverse: A failing valve body or worn shift solenoids produce a noticeable lag or jarring engagement, reducing operator control and increasing drivetrain stress.
- Overheating accompanied by burnt fluid odor: Internal friction from worn bearings or clutch material generates excessive heat, leading to degraded transmission fluid and potential thermal damage to adjacent components.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4644.026.391 |
| Assembly Type | Complete Powershift Transmission |
| Series | WG 200 |
| Estimated Weight | 285 kg (628 lbs) |
| Housing Material | High-strength cast iron |
| Overall Length | 720 mm |
| Overall Width | 510 mm |
| Overall Height | 480 mm |
| OEM Reference | ZF 6 WG 200 |
| Fluid Capacity | Approx. 22 liters |
Compatibility
This complete unit is engineered for the ZF WG 200 series, which includes models such as the WG180, WG200, and WG210. It is commonly used in articulated dump trucks, wheel loaders, and graders from manufacturers like Volvo, Case, and Caterpillar that specify ZF drivetrains. The assembly is also backward-compatible with certain WG180 variants when paired with the correct TRANSMISSION HOUSING (4644101249) or TRANSMISSION HOUSING (4644301402). Always verify bellhousing bolt patterns and input shaft spline counts before installation.
During a full rebuild, the COVER PLATE (4644301298) must be replaced to maintain internal pressure integrity, while the O-RING (0634306323) seals the main housing joint to prevent fluid migration. These components are critical for ensuring the 4644.026.391 assembly operates without leaks or pressure loss.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101249 | TRANSMISSION HOUSING | Main structural casing for gear and clutch assembly |
| 4644301402 | TRANSMISSION HOUSING | Alternate housing variant for specific WG200 builds |
| 4644301298 | COVER PLATE | Seals the upper access port and retains internal pressure |
| 0634306323 | O-RING | Prevents fluid leaks between housing and cover plate |
| 0636305026 | SCREW PLUG | Seals drain and fill ports in the transmission housing |
| 4644301279 | SCREEN SHEET | Filters debris from hydraulic fluid before it enters the pump |
| 4644301088 | SEALING CAP | Protects exposed ports during storage or shipping |
| 4644298503 | REPAIR KIT | Contains gaskets, seals, and O-rings for a full overhaul |
| 4475280079 | SCREW PLUG | High-pressure plug for valve body or accumulator ports |
| 4644121150 | OIL PIPE | Routes pressurized oil between valve body and clutch packs |
