ZF 4699.804.136 GK25 | OEM Genuine Part

Overview

The ZF 4699.804.136 GK25 is a genuine OEM shift cylinder assembly engineered for heavy-duty construction machinery transmissions. This precision component controls clutch pack engagement within the valve body, directly managing gear selection under high torque loads. Positioned as a critical hydraulic actuator inside the transmission housing, the SKU 4699.804.136 ensures smooth ratio changes in wheel loaders, dozers, and graders. When paired with the 4699101043 HOUSING, this part maintains sealed hydraulic pressure for consistent shift timing. The GK25 designation indicates a specific bore diameter and stroke length optimized for ZF’s modular transmission architecture.

Symptoms of Failure

• Delayed or harsh gear engagement — Worn internal seals cause pressure loss, leading to sluggish shifts or sudden clunks when moving from neutral to drive.
• Hydraulic oil seepage around the valve body — Cracks in the cylinder bore or degraded O-rings allow ATF to escape, often pooling near the 4699301106 HOUSING interface.
• Intermittent gear slipping under load — As the piston fails to hold full stroke, the clutch pack partially disengages during uphill operation or heavy digging cycles.
• Erratic shift patterns in cold starts — Thermal expansion differences between the cylinder and the 4699301015 HOUSING COVER create temporary binding, causing missed shifts until the transmission warms.

Technical Specifications

Compatibility

This genuine ZF GK25 cylinder is designed for the WG180, WG200, and WG210 series powershift transmissions commonly found in Volvo, Liebherr, and Caterpillar construction equipment. It also fits select 4WG-200 and 5WG-300 models produced between 2008 and 2020. The part interfaces directly with the 4699301085 COVER and requires proper alignment with the shift rail assembly. Always verify your transmission serial number against ZF’s compatibility chart, as early WG180 units may use a different piston length.

Related Components