Overview
The ZF 4644.162.200 RETARDER for WG200 is a critical hydraulic braking component integrated into the rear of the transmission housing. This OEM genuine part provides continuous, wear-free braking assistance by converting kinetic energy into heat through fluid resistance, significantly reducing service brake wear on heavy-duty vehicles. As a factory-specified unit for the WG 200 Series, the SKU 4644.162.200 directly interfaces with the TRANSMISSION HOUSING (4644101216) and the TRANSMISSION HOUSING (4644301223) to form a sealed oil circuit. This retarder assembly is essential for maintaining safe descent speeds on grades and extending the lifespan of the entire drivetrain.
Symptoms of Failure
- Gradual loss of braking force on long descents: A worn 4644.162.200 will fail to provide adequate hydraulic resistance, forcing the driver to rely heavily on service brakes. This is often the first sign of internal seal degradation.
- Transmission oil overheating and foaming: When the retarder rotor or stator vanes wear, hydraulic efficiency drops, causing excessive heat generation. You may notice oil bubbling or a burnt smell from the transmission vent.
- External oil seepage around the retarder housing: Damaged O-rings or a cracked housing will cause ATF to leak from the joint between the retarder and the GROOVED STUD (0631311009) mounting points. Look for drips near the rear of the transmission.
- Unusual vibration or noise during activation: A failing retarder may produce a low-frequency hum or grinding sound when engaged, indicating worn bearings or a damaged rotor assembly.
Technical Specifications
| Parameter | Specification |
|---|---|
| OEM Part Number | 4644.162.200 |
| Product Type | Hydraulic Retarder Assembly |
| Compatible Series | WG 200 |
| Material | High-strength aluminum alloy housing with hardened steel rotor |
| Dry Weight | Approx. 28.5 kg (62.8 lbs) |
| Overall Diameter | 380 mm |
| Overall Length | 210 mm |
| Max Operating Pressure | 12 bar |
| Max Oil Flow Rate | 180 L/min |
| OEM Reference | ZF 4644.162.200 |
Compatibility
This genuine ZF 4644.162.200 retarder is engineered specifically for the WG 200 Series transmissions. It is also mechanically compatible with the WG180 and WG190 models when used with the correct adapter plate and TYPE PLATE (0730365067) for identification. The unit fits all WG200 variants, including those used in municipal buses, refuse trucks, and heavy distribution vehicles. Always verify the transmission serial number against the OEM specification before installation.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101216 | TRANSMISSION HOUSING | Main structural casing for gear train |
| 4644301223 | TRANSMISSION HOUSING | Rear housing section for retarder mounting |
| 0730365067 | TYPE PLATE | Identification tag for transmission model |
| 0631311009 | GROOVED STUD | Fastener for housing alignment |
| 4644303060 | COVER PLATE | Seals the retarder oil cavity |
| 4644303061 | COVER PLATE | Alternate cover plate variant |
| 0634306525 | O-RING | Hydraulic seal between components |
| 0636305026 | SCREW PLUG | Oil drain or fill port closure |
| 4644301279 | SCREEN SHEET | Filter mesh for oil debris |
| 4644301088 | SEALING CAP | Protects hydraulic ports |
