How to Identify a Hydraulic Pump or Motor With No Tag

To identify a hydraulic pump or motor with a missing or unreadable tag, work out what kind of unit it is first (vane, gear, piston or orbital) from its shape, then look for numbers that outlive the tag: assembly and serial numbers stamped into the casting, the model code stamped on a cover, and part numbers on the parts inside. If nothing readable is left, the mounting flange, shaft spline, port sizes and the machine it came off are almost always enough to place it.

Below: where each brand puts its tag, what the code looks like, and which of our decoders reads it. Most units that reach us with no tag still get identified. The ones that do not usually arrive as a single blurry photo.

Before you scrape any paint: write down the make, model and year of the machine the unit came off, and photograph every face of it as it is. The machine parts manual often lists the pump by its OEM model. That one line can save a day of measuring.

A picture is worth a thousand words. If you are in doubt at any point, stop guessing and send us photos. Our in-house experts work with these units every day and will try to help you identify yours. Email the photos to info@restopower.com or call (810) 882-1171.

Is it a pump or a motor?

Settle this before anything else, because a lot of motors get posted online as "this pump".

Port sizes. A pump that draws from tank usually has a suction port noticeably bigger than its pressure port. A motor that runs both directions usually has two working ports the same size.
A control on the end. A compensator, regulator or adjusting screw on the end cap usually means a variable pump. Kawasaki makes the point on its own units: no regulator and no suction port sized for tank, and you are probably holding a motor.
A charge pump on the back and relief valves guarding both sides of the loop. That is a closed-loop hydrostatic pump, not an open-circuit unit. Sundstrand and Sauer-Danfoss units, Eaton heavy-duty hydrostatics and the Kawasaki K8V all fall here.
A heavy short output shaft and a round body with a gear set at the back. That is a low-speed high-torque orbital motor.

How do I tell a vane pump from a gear, piston or orbital unit?

Shape tells you the family before any number does.

Type	What it looks like	Typical families
Vane pump	Round or oval cartridge body, often a square mounting flange. Singles, doubles and tandems are sections bolted end to end. Denison T-series bodies are rectangular or oval with a removable cover and a cartridge inside.	Vickers V10, V20, 25V-45V, VQ, VMQ. Denison T6, T67, T7.
Gear pump	Compact body, no compensator, inlet and outlet close together.	Vickers GD and G5, Parker (ex Commercial Intertech) PGP and PGM.
Axial piston pump, inline	Longer barrel-shaped body, heavier casting, usually a compensator or regulator on the end cap.	Vickers PVB, PVH, PVQ, PVE. Rexroth A10VSO and A10VO. Oilgear PVWJ, PVM, PVG. Parker PVP. Denison Gold Cup.
Bent axis	Angled housing. The shaft and the cylinder barrel are visibly not in line.	Parker F11 and F12.
Tandem excavator pump	Two pumps back to back on one shaft, usually a small gear pump on the tail for pilot pressure, regulator on top or side.	Kawasaki K3V, K5V, K7V.
Orbital motor	Short and round, a gerotor or geroler section at the back, heavy output shaft.	Char-Lynn, Parker Torqmotor (ex Ross and TRW).
Radial piston motor	Low-speed radial piston motor, usually a wheel or drive motor. The Poclain MS is a multi-cam design with a distributor, cam track and rollers inside.	Poclain MS and MSE, Kawasaki Staffa.

Vane or piston is the call people get wrong most. A vane pump body is built around a round or oval cartridge. A piston pump is longer and heavier, and nearly always carries a compensator or regulator on the end cap. If it has a compensator, it is not a gear pump.

Where is the tag on each brand, and what does the code look like?

Most tags sit on a machined flat or an end cover. The example codes below are taken from our own decoders, so you can match the pattern even if half the characters are gone.

Brand	Where the tag usually is	What the code looks like	Decoder
Vickers / Eaton pumps	Nameplate, or stamped on the housing near the ports. Vane pumps usually on the flat boss near the cover. On a VMQ the model number is stamped on the pump cover. PVH piston pumps also carry an assembly number stamped on the mounting flange.	PVH74QIC-RSF-1S-10-C25-31	Vickers ID guide, model number guide
Vickers valves	Varies by valve family. Photograph every face.	DG4V-3-2A-M-U-H7-60	DG4V / DG5V decoder
Parker	Plate stamped or laser-etched on a machined flat beside or opposite the ports. On a Torqmotor, the flat opposite the ports.	TC0045AS010AAAB (Torqmotor), PGP / PGM gear units	Which Parker is it, Parker decoder
Denison / Parker Denison	Nameplate. Parker branding does not change the code.	T7D-B42-1R00-A1M0, T6C-B22-1R00-C1, Gold Cup P14	Denison decoder, T6 / T7 shaft decoder
Rexroth A10	Nameplate. Besides the type code it carries the material number, serial number, manufacturing date and rotation.	A10VO71DFR/31L-PSC12K68	A10VSO / A10VO decoder
Kawasaki	Plate on the flat face of the main body, or the end cover behind the regulator. On tandems, the side of the front pump. A separate serial number is stamped into the casting.	K3V112DT, K3VL80/B-10RSS-L0/1-H1	Kawasaki ID guide
Oilgear	Nameplate on the housing with the type code and a serial number beside it.	PVWJ-098-A1UV-LDFY-P-1NN-NN	Oilgear ID guide
Sundstrand / Sauer-Danfoss	Nameplate on the housing: model number, date code, part number and serial number.	Date code 88-04 (fourth week of 1988)	Sundstrand ID guide
Char-Lynn / Eaton orbital	A product information tag on every unit. On the W Series brake motor, Eaton's repair manual shows it on the end cap.	101-1083-009, plus a date code of week and last digit of year	Char-Lynn decoder
Eaton heavy-duty hydrostatic	ID tag with model and serial number.	0054 21-960 (Model 54 variable pump)	Eaton heavy-duty guide
Poclain	Nameplate. The first block is the frame.	MS08-2-125-F08-1120-5EGJM	Poclain MS guide

Partial code? Send what you can read with the gaps marked. "PVH74 something RSF" beats nothing.

Tag gone? Look for stamped and casting numbers

A missing plate is not the end of it. Several makers put a second number somewhere that survives a lost plate.

Vickers PVH: Vickers asked for the model code from the nameplate and the assembly number stamped on the mounting flange on every service inquiry. We hold Vickers' own 1990 model-to-assembly cross reference, which traces many older assembly numbers back to a model code.
Vickers VMQ: the model number is stamped into the cover itself, not just on a plate.
Kawasaki: the serial number stamped into the casting survives when the plate does not.
Sundstrand and Sauer-Danfoss: casting numbers on the housing and the end cap help place the series.
Oilgear: the serial is stamped beside the type code, and it settles mid-production part changes.

The parts inside carry numbers too

If the unit is already apart, the internals can identify it. A seal, shaft or cartridge number can point back to the Vickers family. On a Vickers VMQ the cam ring carries an etched arrow that shows its rotation. Denison vane pumps get rebuilt with a different cam ring or shaft than they left the factory with, and when the nameplate and the parts inside disagree, trust the parts.

A punched code is not always a model number. Vickers' 1997 Quality Assured repair manual told its QA service centers to punch a short code into an unmachined surface after every repair: center number, a month letter, the last digit of the year, the tester's initials, and C or W for charge or warranty. If you find something like that, the pump has been rebuilt before, and the internals may not match the original build.

What should I measure if there is no number at all?

Four measurements do most of the work: the mounting pilot, the bolt pattern, the shaft, and the ports. Rotation matters too, and the makers read it looking at the shaft end.

Mounting flange: measure the pilot and the bolt spacing

The pilot is the raised round boss that locates the unit in its drive. Measure it across, then measure center to center between the mounting bolt holes. The standard SAE flange sizes, as Bosch Rexroth dimensions them in data sheet RE 92714:

SAE size	ISO 3019-1 code	Pilot diameter	Bolts	Bolt spacing
A	82-2	82.55 mm (3.25 in)	2	106.5 mm (4.19 in) center to center
B	101-2	101.6 mm (4.00 in)	2	146 mm (5.75 in) center to center
C	127-2	127 mm (5.00 in)	2	181 mm (7.13 in) center to center
C	127-4	127 mm (5.00 in)	4	114.5 mm (4.51 in) square
D	152-4	152.4 mm (6.00 in)	4	161.6 mm (6.36 in) square

A pilot that matches none of these may be a metric ISO 3019-2 flange, which Rexroth and Denison both offer on some builds. Write the number down anyway. It still narrows the frame.

Shaft: count the teeth, measure the diameter

For a splined shaft, count the teeth and measure across the outside of them. For a keyed shaft, measure the diameter and the key width. Standard SAE splines, again as Rexroth lists them to SAE J744:

SAE spline	Nominal size	Teeth and pitch
A (16-4)	5/8 in	9 teeth, 16/32 DP
A-B (19-4)	3/4 in	11 teeth, 16/32 DP
B (22-4)	7/8 in	13 teeth, 16/32 DP
B-B (25-4)	1 in	15 teeth, 16/32 DP
C (32-4)	1 1/4 in	14 teeth, 12/24 DP
C-C (38-4)	1 1/2 in	17 teeth, 12/24 DP
D (44-4)	1 3/4 in	13 teeth, 8/16 DP

The flange and the spline do not always share a letter. A Parker PGP gear pump, for example, is offered with an SAE B flange and an SAE B-B spline, which is exactly why you measure both.

Ports and everything else

Port type and size: four-bolt split flange, O-ring boss, pipe thread or BSP. Measure the thread or the flange bolt spacing on each port, and note which face the ports come out of (side, rear, top).
Case drain: where it is and how big.
Controls: a manual lever, a hydraulic compensator, or a solenoid with a connector, and how many adjusting screws.
Through drive: a cover plate or adapter on the back means it can drive a second pump.
Overall length from the mounting face to the back.

What to send us so we can identify it

The machine: make, model, year, and where on the machine the unit sat.
Photos of every face: shaft end, back end, both sides, top and bottom, in daylight, with the unit wiped clean.
Close-ups of any numbers, including partial ones, stamped or cast, on the housing, cover, flange and end cap.
The shaft: spline tooth count and outside diameter, or keyed diameter and key width.
The flange: pilot diameter, number of bolts and the bolt spacing.
The ports: sizes and type, and which face they leave from, including the case drain.
Rotation, if you know it, viewed from the shaft end.
The fluid it ran on. Mineral oil, water glycol or phosphate ester decides the seal material, whatever the model turns out to be.

Send it through the quote form or call us. A tape measure and a phone camera do most of the work.

Is my pump obsolete, and can it still be fixed?

Often the pump is fine and only the part number stopped existing. Vickers became Eaton and then Danfoss. Parker absorbed Denison, Commercial Intertech, Ross Gear and VOAC, and many of those units are still cataloged under the original name, which is why a Parker search often returns nothing. Sundstrand became Sauer-Sundstrand, then Sauer-Danfoss, then Danfoss, and the numbering carried across.

Valves: many discontinued DG4V numbers were low-volume spool, override and voltage combinations, so the body, spool and coil are usually still obtainable. See obsolete Vickers valve replacements.
Pumps and motors: we hold new old stock, we rebuild, and we cross reference by dimension and function. We also buy new old stock and buy cores, which is part of how obsolete parts stay available.
Repair: our repair and rebuild service starts with a free teardown evaluation, and you get a firm itemized quote before any billable work. Repair work carries a 1-year warranty.

"Obsolete" on a distributor screen often just means that distributor can no longer order it new. It does not mean the parts are gone. Send us the code or the photos before you price a whole new unit and a new mounting kit.

Frequently asked questions

How do I identify a hydraulic pump with no tag?

Work out the type from its shape (vane, gear, piston or orbital), then look for stamped numbers on the casting, cover or flange that outlive the tag. If none survive, measure the mounting pilot, bolt spacing, shaft spline and ports, and note the machine it came off.

What brand is my hydraulic pump?

Look for a nameplate on a machined flat or end cover first. Shape narrows it next: a Kawasaki excavator pump is a tandem with a gear pump on the tail, and a Denison vane pump has a rectangular or oval body with a removable cover. The machine make and model is often the fastest clue.

How do I tell a vane pump from a piston pump?

A vane pump has a round or oval cartridge body and often a square flange. A piston pump is longer, heavier and barrel shaped, and usually has a compensator or regulator on the end cap.

How do I identify a hydraulic motor?

Motors that run both directions usually have two working ports the same size. Orbital motors such as Char-Lynn and Parker Torqmotor are short and round with a heavy output shaft. Every Char-Lynn carries a product information tag, and the first and last groups of its number pick the seal kit.

Where is the stamp on a hydraulic pump?

It depends on the brand. Vickers PVH pumps carry an assembly number stamped on the mounting flange, Vickers VMQ pumps have the model stamped on the cover, and Kawasaki stamps a serial into the casting. Parker puts its plate on a machined flat beside or opposite the ports.

Is my hydraulic pump obsolete?

Often only the part number is. Brands have changed hands many times and many units are still listed under their original maker. New old stock, rebuilding and cross referencing by dimension keep a lot of so-called obsolete pumps running. Send the code or photos before buying new.

What is an SAE B pump flange?

An SAE B two-bolt flange has a 101.6 mm (4.00 in) pilot and bolts 146 mm (5.75 in) apart, as Bosch Rexroth dimensions it in data sheet RE 92714. SAE A is an 82.55 mm (3.25 in) pilot with bolts 106.5 mm (4.19 in) apart.

Can you identify my pump or motor from photos?

Often, yes. Send clear photos of every face, the shaft end, the ports and any stamped numbers, plus the machine it came off. Our in-house experts will try to help you identify it, and if photos are not enough we will tell you which measurements to take. Email the photos to info@restopower.com or call (810) 882-1171.

About the technical information on this page. Figures, procedures and part numbers here come from manufacturer service literature and are provided for reference only. They are only as accurate as the factory data, and the revision we have on file may not be the latest for your unit. Always confirm against the current manufacturer documentation for your exact model and follow safe work practices. RestoPower is not responsible for damage, injury or loss resulting from the use or misuse of this information, or from incorrect assembly, adjustment, installation or operation of any unit.

Send photos and measurements and we will tell you what it is

Every face of the unit, any numbers you can read, the shaft and flange measurements, and the machine it came off. We reply with price, availability and lead time.

Request a quote · (810) 882-1171 · Repair and rebuild service