Overview
The ZF 4657.230.028 DIAPHRAGM is a critical sealing component engineered for the WG190, WG210, and WG211 transmission series. This OEM genuine part functions as a flexible barrier within the hydraulic control system, regulating oil flow and maintaining pressure between the TRANSMISSION HOUSING and the valve body assembly. Positioned precisely in the clutch piston circuit, the diaphragm prevents cross-contamination of fluid circuits while accommodating thermal expansion. The SKU 4657.230.028 is manufactured to ZF’s original specifications, ensuring exact fitment and durability under high-temperature operating conditions.
Symptoms of Failure
- Erratic gear engagement or delayed shifting – When the diaphragm loses elasticity, hydraulic pressure drops cause hesitation between gear changes, particularly in WG210 models.
- Oil seepage at the housing joint – A worn 4657.230.028 allows transmission fluid to escape past the HOUS.FRONT SECT interface, leaving visible drips under the vehicle.
- Intermittent clutch slip under load – Degraded diaphragm material fails to maintain consistent pressure, causing the WG211 series to slip during uphill or towing operations.
- Contaminated fluid with rubber particles – Advanced deterioration releases debris into the oil, often mistaken for clutch wear debris.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4657.230.028 |
| Material | Nitrile rubber (NBR) with fabric reinforcement |
| Outer Diameter | 98.5 mm |
| Inner Diameter | 42.0 mm |
| Thickness | 3.2 mm |
| Weight | 0.045 kg |
| Operating Temperature | -40°C to +150°C |
| OEM Reference | ZF 4657.230.028 |
Compatibility
This diaphragm is designed for ZF WG-series powershift transmissions, including the WG180, WG200, WG190, WG210, and WG211 models. It also fits the WG230 series when used in conjunction with the HOUSING REAR PART and HOUSING REAR SECTION. Always verify the diaphragm orientation against your transmission’s hydraulic schematic before installation.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4657101078 | TRANSMISSION HOUSING | Main structural casing for gear and clutch assembly |
| 4657201166 | HOUS.FRONT SECT | Forward housing section supporting input shaft |
| 4657201168 | HOUSING REAR PART | Rear housing component for output shaft support |
| 4657298101 | HOUSING REAR SECTION | Extended rear housing section for PTO mounting |
| 0631306816 | CYLINDRICAL PIN | Alignment dowel for housing mating surfaces |
| 0636100801 | CAP SCREW | M10 fastener for housing bolt circle |
| 4656301148 | FIXING PLATE | Retainer plate for diaphragm positioning |
| 4657301032 | SCREEN SHEET | Fine mesh filter for hydraulic circuit |
| 4657301033 | SCREEN SHEET | Coarse mesh pre-filter for oil pump |
| 0636100803 | CAP SCREW | M8 fastener for screen sheet retention |
Frequently Asked Questions
Q: Can the 4657.230.028 diaphragm be reused during a rebuild?
A: No. ZF recommends replacing this diaphragm with every overhaul because the rubber compound takes a compression set over time, compromising seal integrity even if no visible damage exists.
Q: How do I differentiate this diaphragm from the WG180 version?
A: The 4657.230.028 has a fabric reinforcement layer visible on the inner lip, whereas earlier WG180 diaphragms use a plain rubber design. Always match the SKU to your transmission’s serial number.
Q: Does this part require special tools for installation?
A: Yes. Use a diaphragm installation tool (ZF part 4657.230.029) to avoid tearing the rubber during insertion into the housing groove. Lubricate with ATF only—never use petroleum-based grease.
📞 Need this part? Contact our ZF specialists:
Email: info@partszf.com |
Phone: +86 158 2286 3467 |
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