Overview
This is the complete ZF 4644.026.378 6 WG 200 Powershift Transmission Assembly, a fully integrated drop-in unit designed for heavy-duty off-highway machinery. As a core component of the WG 200 Series, this assembly houses the torque converter, planetary gear sets, and hydraulic clutch packs within a single, sealed housing. The SKU 4644.026.378 represents the complete, assembled unit, eliminating the need for piecemeal rebuilds. It directly replaces worn or failed transmissions in loaders, graders, and industrial tractors, restoring full power flow from the engine to the driveline.
Symptoms of Failure
When this assembly begins to fail, operators typically notice one or more of the following critical issues. Early diagnosis of these symptoms can prevent catastrophic driveline damage.
- Erratic or delayed gear engagement: The transmission hesitates or slams into gear, particularly when shifting from forward to reverse. This indicates worn clutch packs or degraded hydraulic seals within the 4644.026.378 unit.
- Torque converter shudder under load: A distinct vibration or shudder felt through the chassis when the machine is under heavy load, such as during digging or pushing. This points to internal wear of the stator or turbine assembly.
- External oil leaks at the PTO or bell housing: Hydraulic fluid pooling around the transmission’s mating surfaces, often caused by failed input shaft seals or a cracked housing on the WG 200 assembly.
- Loss of power in higher gears: The machine moves adequately in first or second gear but lacks pulling power in third or fourth, signaling slipping clutches or a failing torque converter lock-up mechanism.
Technical Specifications
| Specification | Value |
|---|---|
| Part Number / SKU | 4644.026.378 |
| Assembly Type | Complete Powershift Transmission |
| Series | WG 200 |
| Number of Speeds | 6 Forward / 6 Reverse |
| Approximate Dry Weight | 385 kg (849 lbs) |
| Overall Length | 710 mm |
| Overall Width | 520 mm |
| Overall Height | 580 mm |
| Primary Material | High-Grade Cast Iron Housing |
| OEM Reference | ZF 4644.026.378 |
Compatibility
This complete unit is engineered specifically for the ZF WG 200 transmission family. While the WG 200 is the primary application, the internal architecture of the 4644.026.378 shares core components with other ZF powershift models. It is a direct fit for the following ZF transmission models and their respective variants:
- ZF WG 200 (Primary application for this SKU)
- ZF WG 180 (Mechanical interface is compatible, though gear ratios differ; verify bell housing pattern)
- ZF WG 150 (Limited compatibility; requires adapter plate for certain applications)
- ZF 6 WG 200 (Direct replacement for all 6-speed variants of this series)
Always cross-reference the mounting flange pattern and torque converter pilot diameter with your specific machine’s engine model before installation. This assembly is most commonly found in Case, New Holland, and JCB heavy equipment.
