Overview
The ZF 4644.026.163 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 torque converter, clutch packs, and planetary gear sets into a single, ready-to-install package. As a core component of the WG 200 Series, it manages power flow from the engine to the driveline, enabling smooth, load-free shifting under full torque. The SKU 4644.026.163 identifies this specific 6-speed forward, 1-reverse configuration with a 555/5 ratio split, making it a direct replacement for worn or failed units in articulated dump trucks, wheel loaders, and graders.
Symptoms of Failure
When the ZF 4644.026.163 assembly begins to degrade, operators will notice distinct performance issues. Recognizing these signs early can prevent catastrophic driveline damage.
- Erratic or delayed gear engagement: A common symptom is a noticeable lag when shifting from neutral to forward or reverse, often accompanied by a harsh “clunk.” This indicates worn clutch discs or degraded hydraulic seals within the assembly.
- Transmission fluid overheating under light load: If the transmission temperature gauge spikes during normal operation (e.g., low-speed maneuvering), it suggests internal leakage or a failing torque converter stator. This is a classic sign of a failing WG 200 powershift unit.
- Oil leaks at the bell housing or output flange: Visible drips of ATF or hydraulic oil around the joint between the transmission and engine, or near the rear output seal, point to worn input shaft seals or a cracked housing. This is a specific failure mode for the 4644.026.163 assembly.
- Loss of power or “slipping” under load: When climbing grades or pushing material, the engine revs increase without a corresponding increase in wheel speed. This indicates worn clutch packs or a failing torque converter lock-up clutch.
Technical Specifications
| Specification | Value |
|---|---|
| Part Number / SKU | 4644.026.163 |
| Series | WG 200 (6 WG 200) |
| Configuration | 6 Forward / 1 Reverse (555/5 Ratio Split) |
| Dry Weight (approx.) | 385 kg (849 lbs) |
| Overall Length (input to output) | 785 mm (30.9 in) |
| Housing Material | High-strength cast iron (GGG-40) |
| Torque Converter Type | Single-stage, 3-element with lock-up clutch |
| OEM Reference | ZF 4644.026.163 (Direct OEM) |
Compatibility
This complete assembly is engineered for the ZF WG 200 Series powershift transmission family. It is a direct fit for the following models and their derivatives:
- ZF 6 WG 200 (all variants with 555/5 ratio)
- ZF WG 180 (with adapter plate modifications; verify bell housing pattern)
- ZF WG 210 (when used in specific articulated truck applications)
- ZF 4 WG 200 (upgrade replacement; requires control valve recalibration)
This unit is commonly found in Volvo A35F and A40F articulated haulers, Case 921F wheel loaders, and Komatsu WA500 series machines. Always cross-reference your original transmission tag with the 4644.026.163 part number to confirm mechanical and hydraulic compatibility.
