Overview
The ZF 4642.306.040 PISTON is a critical hydraulic actuation component engineered specifically for the WG 150 series transmission. This OEM genuine part functions as a pressure-responsive plunger within the valve body assembly, converting hydraulic force into mechanical motion to engage clutch packs and shift gears. Positioned within the main control module, the SKU 4642.306.040 ensures precise oil flow regulation, directly influencing shift timing and torque delivery. When paired with the TRANSMISSION HOUSING (4644101047), this piston maintains the sealed hydraulic circuit necessary for reliable operation in heavy-duty industrial applications.
Symptoms of Failure
- Delayed or harsh gear engagement: A worn 4642.306.040 piston often causes sluggish shifts or abrupt clutch application, particularly when the transmission is cold.
- Internal hydraulic pressure loss: Degraded piston seals lead to fluid bypass, resulting in slipping under load and reduced torque converter lockup efficiency.
- Erratic shift patterns: Operators may notice random gear hunting or failure to hold a selected gear, especially during uphill or heavy-load operations.
- Visible oil contamination: Metal debris or rubber particles in the transmission fluid indicate piston surface wear, often accompanied by a burnt smell from overheated clutches.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4642.306.040 |
| Material | Hardened alloy steel with nitrided surface |
| Outer Diameter | 38.0 mm |
| Overall Length | 72.5 mm |
| Weight | 0.34 kg |
| OEM Reference | ZF 4642.306.040 |
| Seal Type | PTFE lip seal (integrated) |
| Operating Pressure | 12–18 bar |
Compatibility
This piston is primarily designed for the ZF WG 150 series, but it also fits select models in the WG 180, WG 200, and WG 210 families due to shared valve body architecture. The 4642.306.040 is directly compatible with transmissions using the HOUSING (4644301380) and the THREADED BUSH (4644301189) for secure mounting. Always verify the TYPE PLATE (0730365067) on your unit to confirm exact model fitment before installation.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101047 | TRANSMISSION HOUSING | Encloses and protects internal gear train and valve body |
| 4644301380 | HOUSING | Supports piston bore and hydraulic channel alignment |
| 4644301189 | THREADED BUSH | Provides wear-resistant thread for piston retention |
| 0730365067 | TYPE PLATE | Identifies transmission model and serial number |
| 0631311009 | GROOVED STUD | Secures housing alignment during assembly |
| 4644301161 | COVER PLATE | Seals hydraulic access port against debris ingress |
| 0636100621 | HEXAGON SCREW | Fastens cover plate with controlled torque |
| 0631610020 | SET SCREW | Locks threaded bush in permanent position |
| 0634801098 | SEALING RING | Prevents fluid leakage at piston bore interface |
| 4644301117 | FIXING PLATE | Anchors valve body assembly to transmission housing |
