Overview
The ZF 4651.004.021 4 WG 100(500) Powershift Transmission Assembly | Complete Unit is a fully integrated, factory-assembled gearbox core designed for heavy-duty off-highway applications. This complete unit serves as the central power transfer module within the WG 100 series, converting engine torque into controlled hydraulic and mechanical output for wheel loaders, dozers, and material handlers. The SKU 4651.004.021 represents a direct OEM replacement assembly, eliminating the need for piecemeal rebuilds. It integrates seamlessly with the 4651101007: TRANSMISSION HOUSING and the 4651301029: HOUSING to form the structural backbone of the drivetrain.
Symptoms of Failure
- Delayed or harsh engagement – When the complete unit begins to wear, operators notice a pronounced lag between shifting and actual gear engagement, often accompanied by a jarring clunk. This is a classic sign of internal clutch pack degradation or hydraulic pressure loss within the assembly.
- Chronic oil leaks around the bell housing – A failing unit frequently exhibits fluid seepage at the interface between the transmission and the engine. If you spot puddles of ATF under the vehicle, inspect the 0634303928: O-RING and the 4651301024: HOUSING for cracks or warping.
- Gear slipping under load – As internal wear progresses, the transmission will momentarily lose torque during uphill climbs or heavy bucket loads. This symptom indicates worn friction discs or a failing torque converter within the 4 WG 100(500) assembly.
- Unusual whining or grinding noises – Metallic sounds from the transmission casing, especially in neutral or low range, point to bearing fatigue or gear tooth damage inside the complete unit.
Technical Specifications
| Parameter | Value |
|---|---|
| OEM Part Number | 4651.004.021 |
| Assembly Type | 4 WG 100(500) Powershift |
| Dry Weight (approx.) | 185 kg (408 lbs) |
| Housing Material | High-strength cast iron (GGG-40) |
| Overall Length | 720 mm |
| Overall Width | 480 mm |
| Overall Height | 560 mm |
| Fluid Capacity | 12.5 liters (SAE 10W or Dexron III) |
| Max Input Torque | 500 Nm |
Compatibility
This complete unit is engineered for the ZF WG 100 series of powershift transmissions. It is directly compatible with models including the WG 100, WG 120, and WG 150 variants used in compact wheel loaders and telehandlers. While the 4 WG 100(500) designation indicates a 4-speed configuration with a 500 Nm torque rating, it also shares mounting patterns with the WG 180 and WG 200 series when used with the appropriate TRANSMISSION HOUSING adapter. Always verify bell housing bolt patterns before installation.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4651101007 | TRANSMISSION HOUSING | Main structural casing for gear train |
| 4651301029 | HOUSING | Rear cover housing for output shaft |
| 0634303928 | O-RING | Seals housing joint against fluid leaks |
| 4651301024 | HOUSING | Intermediate housing for clutch pack |
| 4651203002 | SCREEN SHEET | Filters debris from hydraulic circuit |
| 4651303005 | SCREEN SHEET | Secondary filtration for oil sump |
| 0636101032 | CAP SCREW | Fastens housing sections together |
| 0630361028 | SEALING CAP | Closes unused hydraulic ports |
| 4475280060 | SCREW PLUG | Seals drain and fill holes |
| 0634303312 | O-RING | Provides seal for screw plug |
