Overview
The ZF 4644.337.013 THREADED BUSH is a precision-machined component engineered specifically for the WG 65 series of off-highway transmissions. This OEM genuine part functions as a critical interface point within the hydraulic control circuit, providing a durable threaded seat for pressure lines and sensor connections. Located inside the main valve body assembly, the 4644.337.013 ensures a leak-free seal under high-pressure conditions while maintaining the structural integrity of the transmission housing. As an original equipment manufacturer (OEM) part, it meets ZF’s exacting tolerances for thread pitch, surface hardness, and corrosion resistance, making it essential for maintaining factory-specified performance in heavy-duty applications.
Symptoms of Failure
- Hydraulic fluid seepage around the valve body: When the 4644.337.013 threaded bush wears or cracks, pressurized transmission oil can escape, leaving visible puddles under the vehicle. This is a common “ZF transmission oil leak” issue that often requires immediate attention.
- Erratic gear engagement or slipping: A compromised threaded bush can disrupt hydraulic pressure to the clutch packs, leading to delayed shifts or “transmission slipping under load” symptoms during operation.
- Increased operating noise from the pump: Air ingestion through a damaged bush seal can cause cavitation, producing a whining or grinding sound that worsens as the “ZF WG65 transmission noise” progresses.
- Intermittent loss of hydraulic pressure: A loose or stripped threaded bush may cause pressure fluctuations, triggering warning lights or “transmission overheating” due to inadequate lubrication flow.
Technical Specifications
| Specification | Value |
|---|---|
| Part Number | 4644.337.013 |
| Material | Case-hardened steel (DIN 1.7131) |
| Thread Size | M18 x 1.5 (internal) |
| Overall Length | 28.5 mm |
| Outer Diameter | 24.0 mm |
| Weight | 0.045 kg |
| Surface Finish | Zinc-nickel plated (ISO 2081) |
| OEM Reference | ZF 4644.337.013 |
| Torque Specification | 45 N·m (dry) |
Compatibility
This threaded bush is designed for the ZF WG 65 series transmission family. Based on its thread pattern and dimensional profile, the 4644.337.013 is also compatible with the following ZF models: WG180, WG200, WG120, and WG150. It is commonly used in construction equipment such as wheel loaders, graders, and dump trucks where the WG65 transmission is factory-installed. For proper fitment, always verify the thread orientation and seating depth against your specific transmission housing variant.
During installation, this threaded bush interfaces directly with the TRANSMISSION HOUSING (4616101111), which provides the primary structural enclosure. Secure fastening is achieved using the HEXAGON SCREW (0636011118), while the HOUSING (4616301304) and HOUSING (4616301309) serve as adjacent mounting points for the valve body assembly. Always replace the O-ring and sealing ring when servicing this bush to prevent premature failure.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4616101111 | TRANSMISSION HOUSING | Main structural casing for gear train |
| 0636011118 | HEXAGON SCREW | Fastener for housing assembly |
| 4616301304 | HOUSING | Valve body mounting bracket |
| 4616301309 | HOUSING | Secondary valve body support |
| 0636011038 | HEXAGON SCREW | Threaded fastener for cover plates |
| 0636016015 | HEXAGON SCREW | High-tensile bolt for flange joints |
| 0631306085 | CYLINDRICAL PIN | Alignment dowel for housing halves |
| 0634313118 | O-RING | Static seal for hydraulic ports |
| 0636304019 | SCREW PLUG | Threaded closure for test ports |
| 0634801152 | SEALING RING | Copper gasket for high-pressure joints |
