Overview
The ZF 4644.306.283 PISTON is a critical hydraulic actuation component engineered for the WG 180, WG 200, and WG 201 series transmissions. This OEM genuine part functions as the primary force-transfer element within the clutch or brake piston assembly, converting hydraulic pressure into mechanical motion to engage or disengage gear sets. Positioned inside the TRANSMISSION HOUSING, the piston must maintain a precise seal and smooth axial travel to ensure consistent shift quality. The SKU 4644.306.283 is manufactured to ZF’s original tolerances, guaranteeing a direct fit and reliable performance under high thermal and pressure loads.
Symptoms of Failure
- Delayed or harsh shifting: A worn piston can cause sluggish engagement or abrupt gear changes, often described as “ZF transmission slipping under load.”
- Internal hydraulic fluid leaks: Degraded piston seals or surface wear lead to oil bypass, resulting in low line pressure and visible drips near the TRANSMISSION HOUSING.
- Erratic clutch engagement: When the piston fails to stroke fully, clutches may drag or fail to lock, producing a “burning clutch smell” or loss of drive in specific gears.
- Increased operating noise: A loose or cracked piston can create a metallic rattling sound from the transmission sump during acceleration.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number (SKU) | 4644.306.283 |
| Material | Hardened alloy steel with anti-corrosion coating |
| Outer Diameter | Approx. 85 mm (3.35 in) |
| Inner Diameter | Approx. 45 mm (1.77 in) |
| Height | 22 mm (0.87 in) |
| Weight | 0.35 kg (0.77 lbs) |
| OEM Reference | ZF 4644.306.283 |
| Seal Compatibility | Requires SEALING RING 0634801098 or SEALING RING 0634801250 |
Compatibility
This piston is specifically designed for ZF’s WG series powershift transmissions. It is a direct replacement for the following models: WG 180, WG 200, and WG 201. These transmissions are commonly found in heavy-duty construction equipment, agricultural tractors, and material handlers. The part interfaces with the GROOVED STUD for alignment and is secured by the TYPE PLATE for identification. Always verify your transmission serial number against the OEM parts catalog before ordering.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101043 | TRANSMISSION HOUSING | Main structural casing for gear and piston assembly |
| 4644301194 | TRANSMISSION HOUSING | Alternative housing variant for WG 200 series |
| 0730365067 | TYPE PLATE | Identification plate for transmission model and specs |
| 0631311009 | GROOVED STUD | Alignment dowel for piston and housing positioning |
| 4644303060 | COVER PLATE | Seals the piston chamber from external debris |
| 4644303061 | COVER PLATE | Alternate cover plate for different clutch packs |
| 0634801098 | SEALING RING | Primary O-ring for piston-to-housing seal |
| 0634801250 | SEALING RING | Backup sealing ring for high-pressure circuits |
| 0636305026 | SCREW PLUG | Closes hydraulic test ports in the housing |
| 0636305019 | SCREW PLUG | Drain or vent plug for the piston cavity |
