Overview
The ZF 0631.501.073 FITTED KEY is a precision-engineered OEM genuine component designed to secure rotating elements within heavy-duty ZF construction machinery transmissions. This fitted key acts as a positive drive interface, transmitting torque between shafts and gears while preventing rotational slippage under extreme loads. Positioned inside the transmission housing assembly, the SKU 0631.501.073 ensures that power transfer remains consistent and backlash-free during demanding operations. When installed correctly alongside the 4108101057: HOUSING and 4108201177: HOUSING, this key maintains the structural integrity of the gear train, making it a critical element for long-term transmission reliability.
Symptoms of Failure
- Transmission gear slipping under load: A worn or sheared fitted key allows the gear to rotate independently on its shaft, causing intermittent power loss during acceleration or heavy digging cycles.
- Abnormal metallic grinding noises: When the 0631.501.073 key loses its tight fit, metal-on-metal contact occurs between the shaft and gear hub, producing a distinct grinding sound that worsens with load.
- Oil contamination with metal particles: Key wear generates fine metallic debris that circulates through the transmission fluid, often detected during routine oil analysis or when draining the 0636302056: SCREW PLUG.
- Vibration at the driveline: A loose fitted key creates rotational imbalance, transmitting noticeable vibration through the transmission case and into the chassis, particularly at operating RPM.
Technical Specifications
| Part Number | 0631.501.073 |
| Product Type | Fitted Key (Parallel Key) |
| Material | Hardened Alloy Steel (C45E / 1.1191 equivalent) |
| Estimated Dimensions | Length: 45 mm | Width: 12 mm | Height: 8 mm |
| Weight | Approx. 0.035 kg |
| OEM Reference | ZF 0631.501.073 |
| Surface Treatment | Phosphated / Oiled for corrosion resistance |
Compatibility
This OEM fitted key is primarily used in ZF WG180, WG200, and WG210 series powershift transmissions commonly found in wheel loaders, telehandlers, and graders. It also appears in select ZF 4WG-200 and 6WG-200 variants. For proper installation, always pair the 0631.501.073 with the corresponding 4108301304: BEARING COVER to ensure correct axial positioning of the shaft assembly.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4108101057 | HOUSING | Encloses and supports the gear train assembly |
| 4108201177 | HOUSING | Secondary housing section for bearing support |
| 0636302056 | SCREW PLUG | Seals oil passages and drain/fill ports |
| 4108301304 | BEARING COVER | Retains shaft bearings and prevents oil leakage |
| 4108306173 | GASKET | Provides sealing between mating housing surfaces |
| 0750110040 | SHAFT SEAL | Prevents fluid egress along rotating shafts |
| 6053108155 | CONTROL COVER | Houses valve spools and shift mechanisms |
| 6053308348 | CONTROL COVER | Alternate cover for multi-speed control modules |
| 0636010188 | HEXAGON SCREW | Fastens housing sections with M10 thread |
| 0636010192 | HEXAGON SCREW | Fastens bearing covers with M12 thread |
Frequently Asked Questions
Q: Can a worn fitted key cause transmission overheating?
A: Yes. When the 0631.501.073 key fails, gear slippage generates excess friction and heat. This can elevate transmission oil temperatures beyond normal operating ranges, accelerating wear on seals and bearings.
Q: Is the 0631.501.073 key reusable after disassembly?
A: No. ZF recommends always replacing the fitted key with a new OEM part during any transmission rebuild. The key is a one-time-use component due to deformation during initial torque application.
Q: How do I verify correct key fitment during installation?
A: The key should slide into the shaft keyway with light hand pressure. If it requires hammering or feels loose, verify the part number and inspect the shaft keyway for damage. Always torque the retaining components to ZF specifications.
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