ZF 0631.501.553 FITTED KEY | OEM Genuine Part

Overview

The ZF 0631.501.553 FITTED KEY is a precision-machined OEM genuine component engineered for secure torque transmission within heavy-duty ZF powershift transmissions. This fitted key acts as a positive mechanical lock between rotating shafts and gear hubs, preventing rotational slippage under extreme load conditions commonly encountered in construction machinery. The SKU 0631.501.553 is specifically designed to seat within the main shaft assembly, where it interfaces directly with the 4699101080: HOUSING to maintain exact gear alignment. Without this fitted key, the entire drivetrain loses its mechanical indexing capability, leading to catastrophic power loss.

Symptoms of Failure

• Intermittent gear slippage under load — When the 0631.501.553 key shears or deforms, the gear hub loses its positive lock, causing sudden disengagement during excavation or grading operations.
• Metallic knocking from transmission housing — A worn fitted key allows radial play between the shaft and gear, producing a distinct clattering noise that worsens as RPM increases.
• Oil contamination with metallic debris — As the key wears, microscopic steel particles enter the lubrication circuit, often found during oil analysis as elevated iron content.
• Hard shifting or gear hang-up — Misalignment caused by a failing key prevents smooth clutch pack engagement, requiring excessive force to move the shift lever.

Technical Specifications

Compatibility

This fitted key is a direct OEM replacement for ZF WG180, WG200, and WG210 series transmissions used in wheel loaders, dozers, and telehandlers. It also applies to select ZF 4WG-200 and 4WG-310 models where the main shaft assembly requires a positive drive key. Always verify the keyway dimensions in your existing 0501329881: HOUSING COVER before installation, as variations exist between early and late production runs. The 0631.501.553 is not compatible with ZF Ecomat or AS Tronic series transmissions.

During rebuild, always inspect the mating 0630513065: SNAP RING for wear, as a loose snap ring can allow axial movement that accelerates key failure. Additionally, replace the 0634306309: O-RING on the housing cover to prevent oil bypass around the key slot area.

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