Commercial Intertech and Parker Gear Pump Identification: P30, P50, P51, P75, P330, P350, P365

To identify a Commercial Intertech or Parker gear pump, read the assembly code on the tag: it starts with P (pump) or M (motor), then the series (30, 31, 50, 51, 75, 76, 315, 330, 350, 365), then codes for the shaft end cover, port end cover, each gear housing and the drive shaft, and the two digits on each gear housing code are the gear width. If the tag is gone, measure the overall width at the port end and the width of each gear housing; the factory chart turns those two numbers into the series and the gear width, and the gear width gives you the displacement.

That is good news if your dump-truck or PTO pump has the tag painted over. A tape, a straightedge and ten minutes usually get you to a series and a gear width, which is most of what you need to buy a seal kit or a replacement.

Which Commercial or Parker gear pump series do I have?

There are two big families. The P30/31, P50/51 and P75/76 are roller bearing pumps: the gear journals run in roller bearings, and pressure-balanced thrust plates sealed with pocket seals close the gear faces. The 315, 330, 350 and 365 are bushing pumps: sleeve bearings instead of rollers, cast bronze thrust plates and channel seals. That matters for seal kits: roller bearing pumps use ring seals to keep bearing oil off the shaft seal, and bushing pumps do not.

Series	Bearings	Gear widths	Displacement per inch of gear	Displacement range (cu in/rev)	Max pressure per Parker catalog
P30 / PGP030	Roller	1/2" to 2"	1.97	0.99 to 3.94	2,500 psi to 1-1/2"; 2,250 psi at 1-3/4" and 2"
P31 / PGP031	Roller, doweled	1/2" to 2"	1.97	0.99 to 3.94	3,000 psi to 1-1/2"; 2,500 psi at 1-3/4" and 2"
P50 / PGP050	Roller	1/2" to 2-1/2"	2.55	1.28 to 6.38	2,500 psi to 1-1/2"; 2,000 psi from 1-3/4"
P51 / PGP051	Roller, doweled	1/2" to 2-1/2"	2.55	1.28 to 6.38	3,000 psi to 1-3/4"; 2,500 psi from 2"
P75 / PGP075	Roller	3/4" to 3"	4.10	3.08 to 12.30	2,500 psi to 2"; 2,250 psi at 2-1/4" and 2-1/2"; 2,000 psi at 2-3/4" and 3"
P76 / PGP076	Roller, doweled	3/4" to 3"	4.10	3.08 to 12.30	3,000 psi to 1-3/4"; 2,500 psi to 2-1/2"; 2,000 psi at 2-3/4" and 3"
315 / PGP315	Bushing	3/8" to 2" (1/8" steps)	1.24	0.47 to 2.48	3,500 psi to 1-3/8", stepping down to 2,500 psi at 2"
330 / PGP330	Bushing	1/2" to 2"	1.97	0.99 to 3.94	3,500 psi to 1-1/2"; 3,250 at 1-3/4"; 3,000 at 2"
350 / PGP350	Bushing	1/2" to 2-1/2"	2.55	1.28 to 6.38	3,500 psi to 1-1/2", stepping down to 2,500 psi at 2-1/2"
365 / PGP365	Bushing	3/4" to 2-1/2"	3.60	2.70 to 9.00	3,500 psi to 2"; 3,250 at 2-1/4"; 3,000 at 2-1/2"

Older Commercial literature rates the same frames lower than the 2001 Parker catalogs, so size a replacement by the rating of the build you are buying.

What is the difference between a P50 and a P51 pump?

Inside each roller bearing pair, the odd number is the higher pressure version. The P31, P51 and P76 carry steel alignment dowel pins, which Commercial says let them run 500 psi higher than the P30, P50 and P75. Gear widths and displacements are the same, so a P50 and a P51 with the same gear move the same oil per turn. In Parker's catalog the PGP050 tops out at 2,500 psi up to a 1-1/2" gear and 2,000 psi from 1-3/4", while the PGP051 holds 3,000 psi up to 1-3/4" and 2,500 psi from 2". From the outside they look alike; Commercial says pulling the port end cover to look for the dowels is the only sure way to tell some series apart.

How do I read a Commercial gear pump model code?

Commercial built every assembly code from the same blocks, in the same order. Here is the two-section P30 example from the factory catalog, P 30B 278 BY OM20-43 D UG10-1, taken apart:

Block	Code in the example	What it tells you
Pump or motor	P	P pump, M motor
Series and model	30B	Series 30, model letter B
1. Shaft end cover	278	Rotation, outboard bearing and mounting flange (decoded below)
2. Port end cover	BY	Unported cover for a multiple unit, with two extended studs
3. Gear housing (front section)	OM20	OM = SAE split flange ports, 1-1/4" one side and 1-1/2" the other; 20 = 2" gear
4. Drive shaft	43	Straight keyed shaft, .9998" diameter, 1/4" x 1-1/4" key
5. Bearing carrier	D	The center casting between sections
6. Gear housing (second section)	UG10	UG = SAE split flange, 3/4" and 1"; 10 = 1" gear
7. Connecting shaft	1	The shaft that drives the second section

A single-section unit stops after the drive shaft, for example M 30A 942 BE YF15-30: a series 30 motor, single, shaft end cover 942, single unported port end cover BE, gear housing YF15 (1" NPT ports both sides, 1-1/2" gear), and keyed shaft 30.

Shaft end cover codes: rotation and mounting

The shaft end cover code is where rotation hides. The leading digit (or two) gives the type, and the last two digits give the mounting flange.

Leading digit	Meaning	Last two digits	Mounting
1	Pump, clockwise, no outboard bearing	05	Round 6-bolt flange (P30)
2	Pump, counterclockwise, no outboard bearing	42	SAE B 4-bolt
3	Pump, double (bi-rotational), no outboard bearing	78	SAE C 4-bolt
4, 5, 6	Same as 1, 2, 3 but with outboard bearing	94	SAE A 2-bolt
9	Motor, no outboard bearing, 1/4" NPT drain	97	SAE B 2-bolt
8	Motor, with outboard bearing, 1/4" NPT drain	98	SAE C 2-bolt (P50, P75, 350, 365)
19 / 18	Motor without / with outboard bearing, 1/4" BSPP drain	80	SAE D 4-bolt (P75)

So a 278 cover is a counterclockwise pump with no outboard bearing on an SAE C 4-bolt flange, and a 442 is a clockwise pump with an outboard bearing on an SAE B 4-bolt. Covers ending 91 and 92 are piggyback covers. On the 300 bushing series, pumps are built CW or CCW and only the motors are bi-directional.

Port end cover codes

On the roller bearing series the first letter is the port type and size and the second is the build: E single pump, I multiple unit with regular studs, Y multiple unit with two extended studs (BE, BI and BY are unported). On the 315 to 365 series, side-ported covers come in mirrored pairs such as EJ and JE, one per rotation.

Gear housing codes: the two digits are the gear width

Two letters for the porting (port style and the size on each side), two digits for the gear width. A multiple-section pump has one gear housing code per section, which is the quickest way to count sections on paper.

Digits	05	07	10	12	15	17	20	22	25	27	30
Gear width	1/2"	3/4"	1"	1-1/4"	1-1/2"	1-3/4"	2"	2-1/4"	2-1/2"	2-3/4"	3"

Housings with an oversized port on one side are marked low pressure only in the catalog. That side is the inlet; never plumb it as an outlet.

The Parker PGP version of the code

Parker's HY09-030 catalog codes the same pumps as PGP or PGM plus the series (030 to 076) and a unit letter (A single, B tandem, C two-piece shaft with outboard bearing), followed by the same shaft end cover, port end cover, gear housing, gear width and shaft blocks. Our Parker gear pump page decodes the PGP315 to PGP365 codes.

What does the 10-digit Commercial number mean?

Commercial also used a 10-digit reference number, written like 312-2915-230, for assemblies and for every part. If you find a number in that pattern on the tag or on a part, it decodes from a factory breakdown sheet:

Digits	Meaning
1st	3 = hydraulic product
2nd and 3rd	Series: 02 = 15H, 03 = 25X, 05 = 37X, 08 = 20 and G series, 12 = 30/31, 13 = 50/51, 14 = C101/C102, 15 = C150/C151, 16 = 75/76, 22 = 365, 23 = 350, 24 = 330, 26 = 315, 27 = 430, 28 = 450, 29 = 465. Obsolete: 01 = D, 04 = 36H, 10 = 15X, 11 = Gearmatic, 17 = 125, 18 = D101, 19 = WM28
4th	Part type: 1 = connecting shaft or gear-shaft combination, 2 = gears, 3 = port end cover, 5 = shaft end cover, 7 = bearing carrier, 8 = gear housing, 9 = assembly
5th	For parts, a modification within the type. For assemblies: 1 = pump, 2 = motor, 3 = special assembly, 4 = sub-assembly, 8 = bill of material
6th and 7th	For gears and gear housings, the size. For assemblies, the 6th digit is the number of gear sections (1 to 5) and the 7th is the first digit of the shaft end cover code
8th to 10th	Serialized. On covers and housings this block also separates rough castings, machined castings and converted housings

Worked example from the catalog's own parts lists: gear set 312-2915-230 is a 30/31 series (12) gear (2) in 1-1/2" width (15). Gear housing 314-8020-100 is a C101/C102 (14) gear housing (8) for a 2" gear (20), and the 100 marks it as a machined casting. Read the same way, an assembly number starting 312-912 is a 30/31 series pump assembly with two gear sections. That is how you count sections from a number when the pump is still bolted to the truck.

How do I identify a Commercial gear pump with no tag?

Commercial published a two-measurement method, and it works on bare castings. If you were hunting for the Commercial Intertech identification PDF, this is the chart from the identifying page of Commercial's gear pump catalog; we do not host that catalog, so every width from it is in the tables below.

1. Look at the port end cover. Match its shape and, most of all, its bolt pattern to the factory views: the round multi-bolt "D" cover, the side-ported 315 to 365 cover, the 37X / 75/76 / 125 cover, or the four-bolt cover used on the 15H, 25X, 20, 30/31 and 50/51.
2. Measure the overall width across that cover and compare it to the table below.
3. Measure each gear housing (the center casting of each section, not the end covers) and convert it to gear width with the second table. Count the housings: that is your number of sections.
4. Split the look-alikes. The 31, 51 and 76 are assembled with dowel pins and the 30, 50 and 75 are not. Commercial says pulling the port end cover to look for dowels is the only way to tell some series apart.

Port end cover style	Series and overall width
Round, multi-bolt "D"	D: 4.50"
Side ported (315 to 365)	315: 4.25", 330: 6.68", 350: 7.12", 365: 7.38" (unported: 4.00", 4.81", 5.75", 6.25")
37X / 75 / 125 style	37X: 5.12", 75/76: 6.13", 125: 7.00"
Four-bolt cover	15H: 4.38", 25X: 4.94", 20: 4.50", 30/31: 4.81", 50/51: 4.94"

A 50/51 and a 25X both measure 4.94". The factory settles it at the shaft end (bearing retention looks different) and with the dowel pin check.

Converting gear housing width to gear width

Measure the housing width, find the nearest value in your series row (rounding up, as Commercial instructs), and read the gear width above it.

Series	Housing width minus	So a 2.75" housing is	Gear width range
P30/P31, P50/P51, 25X, P20	0.75"	2" gear	1/2" (1.25" housing) up to 2" or 2-1/2"
P75/P76, 37X	1.00"	1-3/4" gear	3/4" (1.75" housing) to 3" (4.00" housing); 37X starts at 1/4"
P330, P350, P365	0.50"	2-1/4" gear (P350, P365)	1/2" or 3/4" up to 2" (330) or 2-1/2" (350, 365)

The 37X uses the same 1.00" offset as the P75/P76, from a 1/4" gear in a 1.25" housing up to a 3" gear in a 4.00" housing. If a measurement falls between two values, round up, as the chart says.

How does gear width turn into flow?

Gear width times the displacement per inch from the series table gives cubic inches per revolution. Flow in gpm is displacement times rpm divided by 231, times the pump's efficiency. For a PTO-driven dump pump, Permco's sizing sheet uses engine rpm times the PTO ratio in place of pump rpm.

For a sanity check, Parker's average output figures at 1,800 rpm and 2,500 psi are 29 gpm for a P30 with a 2" gear, 37.5 gpm for a P50 with a 2" gear, 47 gpm for a P50 at 2-1/2", and 59 gpm for a P75 at 2". If your measured flow on a known gear width is well under the catalog figure at the same speed, the pump is worn, and gear pumps do not adjust back into shape.

Which way does my gear pump turn, and can I change it?

Parker's rule: hold the pump with the shaft pointing at you and the idler (driven) gear below the shaft. On a clockwise pump, oil flows left to right, so the inlet is on the left and the outlet on the right. Turning the pump upside down swaps which port is on which side, but it does not change the rotation. Permco states the same thing in shop terms: from the shaft end, belly down, inlet on the left is clockwise.

Inside a P30, P31, P50 or P51, rotation is set by a plug and check valve arrangement in the shaft end cover. Commercial's parts pages show it plainly: the plug in position B gives clockwise rotation, the plug in position A gives counterclockwise, and check valves in both positions give a bi-directional unit (on the P75 and P76 it is item 7 rather than item 5). The shaft end cover code (1, 2 or 3 as the leading digit) records which one left the factory.

The catalogs do not publish a field conversion procedure, and on many builds the port end cover or gear housing is rotation specific too (one port bigger than the other). So treat reversal as a parts question, not a wrench question: decode the code first, then see what has to change. Our pump rotation guide covers the checks that apply to every brand.

How do I identify a dump truck hydraulic pump (Commercial C101, C102, G101, G102)?

A dump truck pump with its control valve built into the pump, worked from the cab by a cable, lever or air shift, may be one of Commercial's pump and valve combinations: C101, C102, G101 or G102. Other makers build dump pumps too, so read the tag first, then match the shaft and mounting below. These pump and valve combinations are built on the same frames. Commercial says the C101/C102 are built on its P30 and P50 frames with 2" and 2-1/2" gears, rated 39 and 48 gpm at 1,800 rpm, and the G101 is based on the P30 with 3/4", 1-1/2" or 2" gears (9.5, 21 or 29 gpm at 1,800 rpm). All are rated to 2,500 psi and 2,400 rpm, and the internal relief is factory set at 2,000 psi.

• 101 vs 102. In the G series, the G101 has twin 1" SAE-BB keyed shafts on a 2-bolt pad, so it can be hooked up CW or CCW without changes. The G102 is the direct PTO-mount version with a single SAE-B splined shaft, so rotation has to be specified. The C series parts lists show the same split, with separate seal kits for each (CM-HC101 and CM-HC102).
• 2-line vs 3-line. A 3-line hookup vents relief oil to tank and allows continuous or intermittent use. A 2-line hookup is for intermittent use only. If a 2-line pump is cooking, that is the first thing to look at.

We stock seal kits for all four: C101, C102, G101 and G102, plus the C101/C102 air shift kit and the G101/G102 air shift kit, on our Parker Commercial dump pump page.

How many gear sections can one shaft drive?

Commercial sizes multi-section pumps by PL factor: pressure times total gear width. A PL 8000 shaft carries 4" of gear at 2,000 psi. If a shaft broke after someone added a section, check that math against the catalog before reusing the same shaft.

What should I send to get the right parts?

• The full code off the tag, or any 10-digit number starting with 3.
• Overall width at the port end, the width of each gear housing, and the number of sections.
• Shaft type (keyed or splined, tooth count) and the mounting flange (bolt count and pilot diameter).
• Port sizes and style on each side, and which way the shaft turns.

Not sure it is a Commercial at all? Start with our guide to identifying a pump with no tag, or the Parker identification router.

Frequently asked questions

Related reading

• Parker PGP and PGM gear pump parts, seal kits and model codes
• Parker Commercial dump pump seal kits and air shift kits
• Hydraulic pump rotation: how to tell and how to change it
• How to identify a hydraulic pump or motor with no tag
• How to identify a Parker hydraulic pump or motor
• Hydraulic pump start-up procedure after a rebuild
• Parker seal kits
• Muncie PTO and pump parts
• Hydraulic calculator: flow, torque and horsepower