ZF 4661.306.003 PISTON for WG 90/WG 94 | OEM Genuine Part

Overview

The ZF 4661.306.003 PISTON is a critical hydraulic actuation component engineered specifically for the WG 90 and WG 94 series transmissions. This OEM genuine part functions as a pressure-responsive plunger within the valve body or clutch pack assembly, converting hydraulic force into mechanical movement to engage or disengage gear sets. The SKU 4661.306.003 is precision-machined to maintain exact clearance tolerances, ensuring consistent shift timing and preventing internal cross-leakage. It operates in direct conjunction with the 4661101020: TRANSMISSION HOUSING, which provides the sealed bore environment necessary for proper piston travel. Without this piston, the transmission cannot modulate line pressure effectively, leading to immediate operational failure.

Symptoms of Failure

• Delayed or harsh engagement when shifting from Neutral to Drive – A worn 4661.306.003 piston allows pressurized fluid to bypass the seal, causing sluggish clutch pack application. This is a common search query for “ZF WG90 shifting delay fix.”
• Intermittent gear slippage under load – As the piston loses its sealing integrity, the transmission may momentarily lose torque transfer, particularly when climbing grades or hauling heavy loads.
• Visible ATF leakage from the transmission housing seam – Cracks or scoring on the piston surface can force fluid past the 4661301046: HOUSING II interface, leaving puddles under the vehicle.
• Erratic shift patterns and flaring between gears – Internal pressure fluctuations caused by a failing piston create unpredictable shift points, often reported as “WG94 transmission hunting for gears.”

Technical Specifications

Compatibility

This piston is designed for the ZF WG 90 and WG 94 series transmissions, which are commonly found in medium-duty trucks, buses, and construction equipment. It is also compatible with the WG180 and WG200 variants that share the same hydraulic circuit architecture. The part interfaces directly with the 4661301093: TUBE, which routes pressurized oil to the piston chamber, and is secured by the 0631306174: CYLINDRICAL PIN that prevents rotational misalignment. Always verify your transmission model suffix (e.g., WG94-2) before ordering, as minor bore diameter variations exist across production years.

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