ZF 4699.804.128 GK25 | OEM Genuine Part

Overview

The ZF 4699.804.128 GK25 is a precision-engineered gear kit designed for the high-torque planetary sections of heavy-duty construction machinery transmissions. This OEM genuine part sits within the final drive assembly, where it manages the critical reduction of rotational speed from the transmission output to the wheel hubs. The SKU 4699.804.128 specifically identifies the complete GK25 gear set, which includes hardened helical gears and synchronizer components that ensure smooth power delivery under extreme load conditions. When paired with the 4699004122: GK25 main shaft assembly, this part forms the core of the transmission’s low-range gearing system.

Symptoms of Failure

When the ZF 4699.804.128 begins to degrade, operators will notice distinct operational issues. Grinding noises during gear engagement are the most common early indicator, often accompanied by difficulty shifting into low-range gears under load. As wear progresses, intermittent gear slipping under heavy excavation loads becomes apparent, particularly when climbing grades. A third critical symptom is metallic debris in the transmission fluid filter, which signals that the gear teeth are spalling. These failure modes directly affect the 4699101098: HOUSING and 4699102132: INPUT components, as damaged gear fragments can score bearing surfaces and housing bores.

Technical Specifications

Compatibility

This GK25 gear kit is engineered for ZF’s WG-series powershift transmissions commonly found in wheel loaders and graders. It is a direct replacement for units in the WG180, WG200, and WG210 transmission families. The part also fits select Ergopower and Ecomix drivelines used in concrete mixer trucks. For proper installation, the 4699103059: OUTPUT shaft must be inspected for runout, as excessive wear on the output splines can cause premature failure of the new gear kit.

Related Components