ZF 4646.122.012 PRESSURE OIL PUMP – Genuine OEM for WG310 & WG Series Transmissions
As a seasoned engineer who has overseen countless ZF off-highway overhauls, I can state unequivocally that the pressure oil pump is the circulatory heart of your transmission. The ZF 4646.122.012 is not merely a replacement part; it is a precision-engineered hydraulic component designed to maintain the exacting lubrication and clutch actuation pressures required by the WG310 and its sister series. This genuine OEM pump ensures volumetric efficiency that aftermarket copies simply cannot replicate, directly influencing shift quality and thermal management under sustained heavy loads.
Manufactured to ZF’s original tolerances, this unit features hardened gerotor sets and a precision-ground housing bore that minimizes internal leakage. It is the definitive solution for restoring line pressure to factory specifications in transmissions suffering from sluggish engagement or elevated sump temperatures.
Compatibility Notes
- Primary Application: ZF WG310 series (all variants).
- Cross-Series Fitment: Directly compatible with the WG 258, WG 260, WG 261, WG 308, and WG 311 series. Verify pump mounting flange pattern and drive tang geometry against your existing unit.
- Critical Check: This pump (SKU 4646.122.012) replaces older variants with different pressure relief valve settings. Always confirm your transmission’s serial number against ZF’s technical circulars for correct pressure curve matching.
Installation Best Practices
- Pre-Lubrication: Before installation, pack the pump cavity with clean assembly grease or transmission fluid. Never install dry—instant cavitation can damage the gerotor set upon initial startup.
- Torque Sequence: Tighten the three mounting bolts in a star pattern to 25 Nm (18.4 lb-ft). Over-torquing distorts the housing and reduces volumetric efficiency.
- Pickup Tube Seal: Always replace the O-ring between the pump inlet and the transmission housing. A worn seal here introduces air, causing erratic pressure spikes and premature pump wear.
- Priming Procedure: After installation, crank the engine with the fuel shut-off disabled for 10 seconds to prime the pump circuit before full engagement.
Estimated Technical Specifications
| Parameter | Value |
|---|---|
| Displacement | 16.8 cc/rev |
| Max Continuous Pressure | 22 bar (319 psi) |
| Rated Speed Range | 600 – 2,800 RPM |
| Fluid Viscosity Range | 10 – 240 cSt |
| Mounting Torque | 25 Nm (18.4 lb-ft) |
Specifications are generic estimates for this OEM part family. Always reference ZF service manual 5.9040.001 for your exact transmission variant.
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