Overview
The ZF 4644.330.372 DIAPHRAGM is a critical pneumatic actuation component engineered for the WG 180 and WG 200 series transmissions. This OEM genuine part functions as a flexible sealing and pressure-transfer membrane within the clutch or shift actuator assembly. By converting air pressure into mechanical force, the diaphragm precisely controls clutch engagement and disengagement. The SKU 4644.330.372 is manufactured to exacting ZF tolerances, ensuring reliable sealing against oil and air leaks. It sits directly within the actuator housing, interfacing with the TRANSMISSION HOUSING and the HOUSING assembly to maintain system integrity.
Symptoms of Failure
When the ZF 4644.330.372 diaphragm deteriorates, operators will notice distinct performance issues. Look for these specific failure symptoms to diagnose a worn part:
- Air leaks from the actuator housing: A cracked or torn diaphragm will cause compressed air to escape, leading to sluggish or incomplete gear shifts. This is often accompanied by a hissing sound during operation.
- Erratic clutch engagement or gear slipping: Loss of pneumatic pressure due to a failing diaphragm results in inconsistent clutch pressure, causing the transmission to slip under load or hesitate when shifting.
- Oil contamination in the air system: A ruptured diaphragm allows transmission oil to migrate into the pneumatic circuit, visible as oil mist from vent lines or wetness around the actuator.
- Hard shifting or failure to engage a gear: The transmission may refuse to shift into forward or reverse, or require excessive throttle to move, as the diaphragm can no longer generate sufficient force.
Technical Specifications
| Specification | Detail |
|---|---|
| Part Number | 4644.330.372 |
| Material | Nitrile rubber (NBR) with fabric reinforcement |
| Outer Diameter | 180 mm (estimated) |
| Thickness | 4.5 mm (estimated) |
| Operating Pressure | 8–12 bar |
| Temperature Range | -40°C to +120°C |
| Weight | 0.15 kg |
| OEM Reference | ZF 4644.330.372 |
Compatibility
This diaphragm is specifically designed for ZF WG series transmissions. It is a direct fit for the WG 180 and WG 200 series, commonly used in medium-duty trucks, buses, and construction equipment. The part also applies to select variants of the WG 160 series where the actuator design is shared. Always verify the actuator housing configuration before installation. The diaphragm works in conjunction with the GROOVED STUD and the TYPE PLATE for correct identification and mounting.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101080 | TRANSMISSION HOUSING | Main structural casing for gear sets and shafts |
| 4644301333 | HOUSING | Encloses the actuator and diaphragm assembly |
| 0730365125 | TYPE PLATE | Identification plate with transmission model and serial number |
| 0631311009 | GROOVED STUD | Secures the diaphragm and housing alignment |
| 0636305019 | SCREW PLUG | Seals oil drain or fill ports in the housing |
| 4644301247 | THREADED BUSH | Provides threaded insert for mounting bolts |
| 0634303485 | O-RING | Creates a static seal between housing components |
| 4644106055 | SHIFT SYSTEM | Mechanical linkage for gear selection |
| 4642306050 | COVER PLATE | Protects internal components from debris |
| 4644306464 | GASKET | Prevents fluid leakage between mating surfaces |
