Overview
The ZF 4644.330.297 DIAPHRAGM is a critical pneumatic actuation component engineered specifically for the WG 200 Series transmission. Positioned within the shift cylinder assembly, this OEM genuine part converts air pressure into precise mechanical force to engage and disengage gear clutches. The SKU 4644.330.297 ensures a factory-spec seal between the piston and housing, maintaining consistent hydraulic pressure for smooth power delivery. Without this diaphragm, the transmission cannot modulate gear changes under load, making it essential for heavy-duty commercial vehicles operating in demanding environments.
Symptoms of Failure
- Delayed or harsh gear engagement – When the 4644.330.297 diaphragm loses elasticity, air pressure bleeds past the seal, causing sluggish shifts or abrupt clutch engagement. This often manifests as a “clunk” when moving from neutral to drive.
- External oil leaks near the shift cylinder – A cracked or perforated diaphragm allows transmission fluid to escape past the piston, leaving visible drips on the housing. This is frequently misdiagnosed as a failed 0634306323 O-RING.
- Intermittent gear slipping under load – As the diaphragm deteriorates, it cannot maintain adequate clamping force on clutch packs, resulting in RPM flare during uphill climbs or heavy hauling. This symptom worsens as operating temperatures rise.
- Air system pressure loss – A ruptured diaphragm causes compressed air to vent into the transmission sump, reducing overall pneumatic system efficiency and triggering low-pressure warnings on the dash.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4644.330.297 |
| Material | Nitrile rubber (NBR) with fabric reinforcement |
| Outer Diameter | 180 mm (7.09 in) |
| Inner Diameter | 95 mm (3.74 in) |
| Thickness | 4.5 mm (0.177 in) |
| Operating Pressure | 8–12 bar (116–174 psi) |
| Temperature Range | -40°C to +120°C (-40°F to +248°F) |
| Weight | 0.28 kg (0.62 lbs) |
| OEM Reference | ZF 4644.330.297 |
Compatibility
This diaphragm is a direct fit for the ZF WG 200 Series, including the WG180, WG200, and WG210 models. It also cross-references to select ZF Ecomat 4HP and 5HP variants where the shift cylinder uses the same 180mm bolt pattern. Always verify the piston diameter matches your unit; the 4644.330.297 is not compatible with the older WG 160 series. For complete housing integrity, pair this diaphragm with a new 4644101249 TRANSMISSION HOUSING or 4644301402 TRANSMISSION HOUSING if cracks are present. The 4644301298 COVER PLATE must also be torqued to spec to prevent diaphragm distortion during installation.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101249 | TRANSMISSION HOUSING | Main structural casing for gear train |
| 4644301402 | TRANSMISSION HOUSING | Alternative housing variant for WG200 |
| 4644301298 | COVER PLATE | Seals the shift cylinder cavity |
| 0634306323 | O-RING | Static seal between housing and cover |
| 0636305026 | SCREW PLUG | Closes oil drain or test ports |
| 4644301279 | SCREEN SHEET | Filters debris from hydraulic fluid |
| 4644301088 | SEALING CAP | Protects pneumatic inlet from contamination |
| 4644109044 | PARKING BRAKE | Spring-applied parking brake assembly |
| 0501211070 | BRAKE | Service brake friction component |
| 0501317036 | PISTON | Hydraulic actuation piston for clutch pack |
