Overview
The ZF 4644.306.264 PISTON is a critical hydraulic actuation component engineered for the WG 180 and WG 200 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 gear sets. Precision-machined from high-strength alloy, the SKU 4644.306.264 ensures a tight seal within the piston bore, directly influencing shift quality and torque capacity. When paired with a robust TRANSMISSION HOUSING (4642101109) or a TRANSMISSION HOUSING (4642301205), this piston maintains the structural integrity required for heavy-duty industrial applications.
Symptoms of Failure
- Delayed or harsh gear engagement: A worn piston loses sealing capability, causing sluggish shifts or abrupt clunking as hydraulic pressure bleeds off.
- Internal transmission oil leaks: Cracks or scoring on the piston surface allow ATF to bypass seals, leading to low fluid levels and puddling under the bell housing.
- Erratic clutch slip under load: When the piston fails to hold pressure, the clutch pack slips during acceleration, producing a burning smell and reduced power transfer.
- Unusual whining or grinding noises: A seized or misaligned piston can create metal-on-metal contact within the drum, generating high-pitched sounds during operation.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4644.306.264 |
| Material | Hardened alloy steel with anti-corrosion coating |
| Outer Diameter | ~120 mm (estimated) |
| Inner Diameter | ~85 mm (estimated) |
| Height | ~45 mm (estimated) |
| Weight | 0.85 kg (1.87 lbs) |
| OEM Reference | ZF 4644.306.264 (Genuine) |
| Seal Type | Integrated PTFE lip seal groove |
Compatibility
This piston is specifically designed for the ZF WG 180 and WG 200 transmission families, which include the WG 100 Series, WG 150 Series, WG 180 Series, WG 200 Series, and WG 201 Series. It is a direct fit for models requiring a high-pressure actuation piston in the forward clutch or direct clutch drum. For complete assembly, ensure the piston is installed with a new GROOVED STUD (0631311009) to secure the piston retainer, and verify the TYPE PLATE (0730365125) matches your transmission serial number for correct revision identification.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4642101109 | TRANSMISSION HOUSING | Main structural casing for gear train |
| 4642301205 | TRANSMISSION HOUSING | Alternate housing variant for WG series |
| 0730365125 | TYPE PLATE | Identification plate with serial number |
| 0631311009 | GROOVED STUD | Retaining stud for piston assembly |
| 4642301168 | SCREEN SHEET | Oil filter screen for hydraulic circuit |
| 4642301169 | SCREEN SHEET | Secondary oil filter screen |
| 0636100621 | HEXAGON SCREW | Fastener for housing assembly |
| 4642301186 | SCREEN SHEET | Fine mesh screen for valve body |
| 4644106231 | SHIFT SYSTEM | Complete shift actuator assembly |
| 4644306470 | GASKET | Sealing gasket for piston bore |
