Overview
The ZF 4644.026.250 6 WG 200(400/3) Powershift Transmission Assembly is a complete, factory-matched unit designed for heavy-duty off-highway applications. As the core drivetrain component in the WG 200 series, this assembly integrates the torque converter, planetary gear sets, and hydraulic control system into a single, ready-to-install package. The SKU 4644.026.250 specifically denotes a 6-speed configuration with a 400/3 converter ratio, engineered for loader, dozer, and material handler platforms. This complete unit eliminates the need for piecemeal component sourcing, ensuring correct gear alignment and hydraulic pressure integrity from the first start-up.
Symptoms of Failure
When the ZF 4644.026.250 assembly begins to degrade, operators typically notice distinct performance issues. Delayed engagement or gear slipping under load is a primary indicator, often caused by worn clutch packs or degraded sealing rings within the hydraulic circuit. Another common failure mode is erratic shifting or harsh direction changes, which points to a failing torque converter lock-up clutch or a compromised valve body. External oil leaks at the PTO housing or converter bell housing are also frequent, resulting from fatigued shaft seals or cracked gasket surfaces. Finally, abnormal whining or grinding noises from the transmission sump suggest advanced bearing wear or planetary gear tooth damage, requiring immediate replacement of the complete unit.
Technical Specifications
| Specification | Value |
|---|---|
| OEM Part Number | 4644.026.250 |
| Series | WG 200 |
| Configuration | 6-speed forward / 3-speed reverse |
| Converter Ratio | 400/3 (3.0:1 stall torque ratio) |
| Dry Weight (approx.) | 385 kg (849 lbs) |
| Overall Length | 725 mm |
| Input Housing Material | High-strength cast iron (GGG-40) |
| Max Input Torque | 1,200 Nm |
| Oil Capacity | 28 liters (with filter and cooler) |
| Mounting Pattern | SAE 3 with 14-inch flywheel |
Compatibility
This complete powershift assembly is primarily designed for the ZF WG 200 series transmissions, including the WG 200 (400/3) and WG 200 (400/2) variants. It is also a direct replacement for units originally installed in ZF WG 180 series applications when paired with the correct adapter plate (not included). The 4644.026.250 assembly is commonly found in Volvo L120, Case 921, and Kawasaki 95ZV wheel loaders, as well as Komatsu WA380 and CAT 950 series machines that have undergone a ZF conversion. Always verify the bell housing pattern and PTO configuration against your original unit before installation.
Additional Notes for Installation
- Requires a ZF-approved hydraulic oil (e.g., ZF TE-ML 03 or 07 specification).
- Torque converter bolts must be replaced with new OEM-grade fasteners.
- Ensure the transmission control unit (TCU) is programmed for the 6-speed WG 200 profile.
