Overview
The ZF 4166.339.185 CIRCUIT COVER is a critical sealing and protective component designed specifically for the WG 65 Series transmission. This OEM genuine part encloses the valve body or control circuit housing, safeguarding internal hydraulic passages from contamination and maintaining precise oil pressure for smooth gear shifts. The SKU 4166.339.185 ensures a factory-spec fit, preventing fluid bypass and supporting the structural integrity of the transmission assembly. When installed alongside the TRANSMISSION HOUSING, this cover forms a sealed chamber that directs oil flow to critical components like the OUTPUT shaft.
Symptoms of Failure
- Hydraulic fluid seepage around the cover perimeter: A worn or warped circuit cover often leads to visible oil leaks near the valve body, causing low fluid levels and erratic shifting.
- Delayed or harsh gear engagement: When the cover fails to seal properly, pressure drops occur, resulting in sluggish clutch packs or abrupt shifts during acceleration.
- Contaminated transmission fluid: Cracks or deformation in the cover allow dirt and debris to enter the hydraulic circuit, accelerating wear on the OUTPUT FLANGE and internal seals.
- Overheating transmission: Loss of oil pressure from a compromised cover reduces lubrication efficiency, leading to elevated operating temperatures and potential damage to the HEXAGON SCREW mounting points.
Technical Specifications
| Specification | Detail |
|---|---|
| Part Number | 4166.339.185 |
| Material | Die-cast aluminum alloy with corrosion-resistant coating |
| Dimensions (L x W x H) | 210 mm x 140 mm x 35 mm (estimated) |
| Weight | 0.85 kg (1.87 lbs) |
| OEM Reference | ZF 4166.339.185 |
| Mounting Hardware | Compatible with HEXAGON SCREW (M8 x 25) and HEXAGON SCREW (M10 x 30) |
| Sealing Components | Requires O-RING and SEALING RING for proper installation |
| Additional Fasteners | Uses CYLINDRICAL PIN for alignment; SCREW PLUG for drain access |
Compatibility
This circuit cover is engineered for the ZF WG 65 Series transmission family, which includes models such as WG65, WG80, WG100, WG120, WG150, WG180, and WG200. It is also compatible with select ZF Ecomat and ZF Ecolife variants that share the same valve body architecture. Always verify fitment by cross-referencing the SKU 4166.339.185 with your transmission serial number, as variations in the TRANSMISSION HOUSING casting may require specific hardware like the HEXAGON SCREW.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4616105402 | OUTPUT | Transfers torque from the transmission to the driveline |
| 4005303005 | OUTPUT FLANGE | Connects the output shaft to the propeller shaft |
| 4616101119 | TRANSMISSION HOUSING | Main structural casing that encloses all internal gears and shafts |
| 0636011038 | HEXAGON SCREW | Secures the circuit cover to the transmission housing |
| 0636011118 | HEXAGON SCREW | Fastens the output flange to the output shaft |
| 0636016015 | HEXAGON SCREW | Mounts the transmission housing to the bell housing |
| 0631306085 | CYLINDRICAL PIN | Aligns the circuit cover during assembly |
| 0634313118 | O-RING | Provides a hydraulic seal between the cover and housing |
| 0636304019 | SCREW PLUG | Seals the oil drain or fill port on the cover |
| 0634801152 | SEALING RING | Prevents leaks at threaded connections |
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