ZF 4699.823.008 GP21 | OEM Genuine Part

Overview

The ZF 4699.823.008 GP21 is a high-precision hydraulic control valve assembly engineered for the demanding environments of construction machinery. Positioned within the valve body of ZF powershift transmissions, this OEM genuine part regulates clutch pressure and fluid routing to ensure smooth gear engagement. The SKU 4699.823.008 is a direct replacement component, designed to restore original shift quality and prevent premature wear in heavy-duty loaders, graders, and dozers. When paired with a BASIC PARTS kit and a HOUSING assembly, this GP21 unit forms the core of the transmission’s hydraulic logic.

Symptoms of Failure

• Erratic or delayed gear engagement: When the GP21 spool or bore wears, operators experience hesitation or harsh shifting, especially when transitioning from forward to reverse under load.
• Internal hydraulic pressure loss: A worn 4699.823.008 can cause gradual pressure drop, leading to clutch slippage and overheating during extended operation in construction machinery.
• Oil contamination from metallic debris: As the valve body erodes, fine metal particles circulate through the system, accelerating wear on the GEAR SHAFT and PLANET CARRIER assemblies.
• Intermittent neutral condition: A sticking GP21 valve may cause the transmission to unexpectedly drop into neutral, creating a safety hazard on job sites.

Technical Specifications

Compatibility

This GP21 valve assembly is primarily compatible with ZF WG180, WG200, and WG310 series powershift transmissions commonly found in construction machinery such as wheel loaders, backhoes, and telehandlers. It also fits select ERGOPOWER and ECOMIX models where the hydraulic control block uses the 4699.823.008 designation. Always verify the transmission serial number against the OEM parts catalog before installation. For a complete rebuild, consider replacing the INNER DISK CARRIER and RING GEAR simultaneously.

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