Hydrostats

How to Choose a Hydrostat Pump

A hydrostat has to match the closed-loop system it feeds, not just bolt up. Confirm these before ordering:

• Size and displacement — physical frame size plus rated displacement (cc/rev or cu in/rev) so output flow matches the paired motor.
• Material and build — housing and internal construction suited to the fluid and duty cycle of the drive system.
• Rating and capacity — operating and peak pressure rating, along with rated flow at your input speed; verify both against the equipment spec.
• Application — the machine and drive function (ground travel, conveyor, fan, or auxiliary drive) the pump was built for.
• Shaft and porting — shaft diameter, key or spline, mount pattern, and port type and thread, all of which should mirror the unit coming off.

Which Pump Is Right for the Job?

A hydrostat is purpose-built for closed-loop hydrostatic drive, so it is not interchangeable with open-circuit pumps. If your machine uses a separate reservoir, control valve, and return line, you likely need a different type. Gear Pumps handle high-pressure open-circuit duty in compact, economical packages. Hydraulic Vane Pumps run quieter at steadier mid-range flow. Piston Pumps cover the highest pressures and variable-displacement control. Clutch Pumps engage on demand off an engine accessory drive. When you are unsure, compare your tag data against the full Hydraulic Pumps range or send it to us to confirm fit.

Complete the System

A hydrostatic drive is only as reliable as the parts around the pump. Pair the right actuator from our Hydraulic Cylinders range for lift or auxiliary functions, and seal the circuit with correctly rated Hydraulic Fittings so port threads and flow paths match without leaks or restriction.

Cross-Referencing an Obsolete Hydrostat

Hydrostat pumps on aging equipment are often discontinued, and a faint casting number can stall a repair for days. Northern Hydraulics has cross-referenced drive pumps and replacement parts since 1963, working from the data you can read off the unit — tag or casting numbers, displacement, shaft, mount, and port details. If your part number returns nothing or the original maker is gone, photograph the tag, note the machine it came off, and request a cross-reference.