Skid Steer Hydraulic Pump Replacement: What to Match Before You Order

Confirm which pump you are replacing

"Skid steer hydraulic pump" can mean two different parts. On many machines, travel is driven by tandem hydrostatic piston pumps: two pumping units joined end to end, each feeding a reversible hydrostatic motor for one side of the machine. A separate gear pump supplies the lift and tilt cylinders and the auxiliary couplers. Bobcat's S76 specification page lists both an engine-driven gear-type pump and "infinitely variable tandem hydrostatic piston pumps" on the same loader, and an older John Deere skid-steer brochure describes the same split between tandem drive pumps and a gear-type loader pump.

That layout is common, but it is not universal, and it varies by make, model and year. Confirm it from your operator or service manual, or from the machine itself, before you search. Note which function the request is about (travel, or lift, tilt and auxiliary flow) and pass that on to the supplier. It tells them which pump you mean. It does not, on its own, prove which component has failed.

Naming the pump type is only the start. Pump manufacturers offer tandem hydrostatic pumps for skid steers in several displacements and with different displacement controls; Danfoss, for example, lists its MP1T tandem pump in 28 cc and 32 cc sizes and its H1T tandem pump in four sizes from 45 to 68 cc. "Tandem pump" or "hydrostatic pump" therefore narrows the search but does not identify a replacement.

Lock the machine identity and configuration

Start with the machine, not the pump. Record the make, the full model designation and the serial number or PIN from the machine's identification plate, and photograph the plate rather than copying it from memory. Bobcat notes that the serial number is important for identifying and sourcing the right parts, and that the plate's location varies by machine type, series and year; its serial number location guide shows where to look on Bobcat equipment. Other brands use their own plates and serial or PIN formats, so record exactly what yours shows.

Then record the options that may change the hydraulic system. High flow is the obvious one: Bobcat lists the S76's pump capacity as 88.1 l/min, and 114.7 l/min with the high-flow option. That is one model's figure, not a typical value, but it shows why "same model" is not enough on its own. Note whether the machine has high flow, any aftermarket hydraulic changes, and anything else that differs from the base specification.

If you need a general method for collecting machine and part evidence, the general guide to finding the right skid steer part covers the identification plate, part markings and photographs in more detail.

Record the markings and displacement

Before the old pump is cleaned, painted or scrapped, photograph every tag, stamping and casting mark on it, including any on a second section bolted to it. Record each one exactly as it appears, and note which body or section it came from. If a mark is unreadable, write "unreadable" rather than guessing.

Displacement is the volume a pump moves in one turn of its shaft, written per revolution, for example in cm³/rev or in³/rev. Pump makers' ordering codes treat displacement as its own field, separate from rotation, shaft, flange and ports. A pump with the right displacement can still have the wrong shaft or ports, and the reverse is also true. Record displacement if it is marked or documented for your machine. Do not estimate it from the pump's size.

Gear pump: match rotation, shaft, flange and ports

For the loader or auxiliary gear pump, record these interfaces one at a time. Parker's gear-pump catalogue, for example, builds its ordering code from separate fields for displacement, rotation, shaft, flange and ports. That is a good model for your own record.

• Rotation. Pump rotation is given as clockwise or counter-clockwise, looking at the drive shaft. Parker's catalogue warns to drive a pump only in its indicated direction. Record the direction from the shaft end, and do not assume that an opposite-rotation pump can be used.
• Shaft. Record the shaft type: splined, keyed, tapered or another style. For a splined shaft, note the tooth count and, if it is documented, the spline standard or pitch. Measure the diameter and the length that engages the drive.
• Mounting flange. Record the flange size and bolt pattern: two-bolt or four-bolt, and the SAE A, B or C designation if it is known. Measure the pilot diameter that locates the pump.
• Ports. Record whether the inlet and outlet ports are on the side or the rear, and their connection style: threaded O-ring boss, split flange or other. Note their size and their position relative to the shaft.

Tandem hydrostatic pump: record the extra interfaces

A drive pump has the same basic interfaces (rotation, input shaft, mounting flange and main ports) plus several a simple gear pump does not. The Danfoss H1P technical information shows the kind of options a closed-circuit hydrostatic pump specification carries. It is an example of the fields to record, not the pump in any particular skid steer.

• Case drain. Closed-circuit piston pumps such as the Danfoss H1 have case drain ports. Record where they are and what fittings are on them.
• Charge pump and filtration. Hydrostatic pumps such as the Danfoss H1 can include a charge pump and charge or filtration ports. Record what is fitted and what connects to it.
• Displacement control. Note how the pump is controlled: manual linkage, hydraulic pilot or electric, with any connectors or solenoids, and photograph the control and its wiring.
• Attached pumps and sections. Hydrostatic pumps can have an auxiliary mounting pad, in SAE A, B or C sizes on the Danfoss example, that carries another pump. Gear pumps can also be built as two- or three-section assemblies with common or separate inlets. If a gear pump or another section is bolted to the back of the pump you are replacing, record whether it stays with the old unit or must move to the new one.

Fill in a pump identification record

Put everything in one record, so that you and the supplier are comparing the same facts. Write "unknown" where you lack evidence, rather than leaving a blank or guessing.

Test a listing's compatibility claim against your record

The listings that rank for this search are mostly organised by brand and model ("fits model X"). Treat those lists as a starting point and check each offer against your record before you order:

• 1. Confirm that the listing is for the same pump function: a drive pump, not a loader pump, or the other way round.
• 2. Check that the listing covers your serial range and your options, such as high flow. As the Bobcat example shows, an option can change the pump capacity on the same model.
• 3. Compare each field in your record (rotation, shaft, flange, ports, sections and, for a drive pump, case drain, charge and control) with what the listing or quote states. Mark every field the seller does not address as unanswered.
• 4. Send the unanswered fields back as specific questions, for example: "What is the rotation viewed from the shaft end?" or "Is the rear section included?" A reply that only repeats "fits your model" does not answer them.

What this checklist does not cover

This guide is about identifying and matching a pump before you order. It does not cover diagnosing a failed pump, removing or installing one, priming or start-up, or setting system or relief pressures. Use your machine's operator and service manuals for those, and have a qualified technician do the work. Leaking flat-face quick couplers are a separate problem with their own guide on this site.

Send the record for a pump match

When the record is complete, start from the hydraulic pump parts category. It asks for the same kinds of evidence: shaft, rotation, flange, ports, case drain, markings and how the pump couples to the engine or to other sections.