ZF 4644.306.076 ORIFICE for WG201/WG65 | OEM Genuine Part

Overview

The ZF 4644.306.076 ORIFICE is a precision-machined hydraulic flow control component engineered specifically for the WG 201 and WG 65 series transmissions. This OEM genuine part regulates oil pressure and flow within the valve body assembly, ensuring consistent clutch pack engagement and smooth gear shifts. Positioned within the hydraulic control circuit, the orifice restricts fluid passage to dampen pressure spikes and maintain stable lubrication to critical rotating assemblies. The SKU 4644.306.076 is manufactured to ZF’s exacting tolerances, guaranteeing a direct fit and reliable performance in heavy-duty industrial drivetrains. When paired with a properly functioning 5838109012: DIFFERENTIAL, this orifice helps maintain balanced hydraulic pressure across the entire transmission system.

Symptoms of Failure

• Erratic or delayed gear engagement: A worn or clogged orifice disrupts hydraulic timing, causing hesitation when shifting from neutral to drive or reverse.
• Intermittent transmission slipping under load: When the orifice fails to maintain proper backpressure, clutch packs may slip during acceleration, especially in WG65 units operating at high torque.
• Visible oil seepage around the valve body: Degraded orifice seals or bore wear can lead to external hydraulic fluid leaks, often mistaken for a gasket failure.
• Harsh or jarring shift quality: Loss of flow restriction results in abrupt clutch engagement, producing a noticeable “clunk” during gear changes.

Technical Specifications

Compatibility

This orifice is engineered for the ZF WG 201 and WG 65 series powershift transmissions. It is also compatible with the WG180, WG200, and WG210 models that share the same valve body architecture. The part integrates directly with the 0750117075: TAPER ROLLER BEARING support assembly and the 2093209023: DIFFERENTIAL unit found in these drivelines. For complete hydraulic circuit restoration, technicians often replace this orifice alongside the 5838300626: DIFFERENTIAL HOUSING to eliminate any debris contamination.

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Frequently Asked Questions

Q: Can I install the ZF 4644.306.076 orifice without replacing the surrounding seals?
A: It is strongly recommended to replace all O-rings and gaskets in the valve body area when installing this orifice. Contaminated or aged seals can introduce debris that will clog the new orifice within hours of operation.

Q: How do I verify if my WG201 transmission requires this specific orifice?
A: Check the hydraulic pressure at the clutch modulation test port. If readings fluctuate more than 15 psi during steady-state operation, the 4644.306.076 orifice is likely worn or obstructed. Always cross-reference your transmission serial number with ZF’s parts catalog.

Q: Is this orifice interchangeable with the WG180 series?
A: Yes, the WG180, WG200, and WG210 models use the same valve body bore dimensions. However, always compare the orifice diameter—using a 1.2 mm orifice in a system designed for 1.5 mm can cause delayed shifts and overheating.