A10VO Pumps: Through Drive, Seals and Ports — Three Things to Check Before You Order a Replacement
An A10VO axial piston pump looks simple from the outside, but its type code quietly answers three questions that decide whether a replacement will bolt on and run correctly:
- Does the original pump drive a second pump at the back (through drive)?
- Which seal material does it use — FKM or the older NBR (nitrile) version?
- Which working-port codes and drain-port arrangement does the code show?
All three are part of the model code on the nameplate. Here is how to read them so you order the right pump the first time.
1. Through drive: is your pump a “two-pump” pump?
Many A10VO pumps are built with a through drive: a second shaft extends out of the rear of the pump so a second pump (another piston pump or a gear pump) can be mounted directly behind it, driven by the same input shaft. One input shaft, two or more pumps.
In the model code, look at the through-drive position (near the end of the code):
- N00 — no through drive. The pump has no rear shaft for a second pump.
- K.. codes (K01, K52, K68, K04, K07, K24 …) — classic through drive with a splined coupling. The hub size and spline must match the second pump’s shaft, e.g. 5/8″ 9T, 3/4″ 11T, 1″ 15T, 1¼” 14T…
- U.. codes (U00 … U17) — the universal through drive, used on Series 32 units with their special port plates (22/32). Note that U00 still counts as a through-drive pump: the shaft is there, the coupling is not, and the opening is covered — it is prepared for adding a second pump later.
How to recognise it on the machine: look at the back (non-drive) end. If a second pump is bolted there with its own mounting flange and you can see a splined shaft between the two, it is a through-drive setup and the replacement must keep it. If the back is a plain cover, the machine probably runs N00 — but check the code, because a second pump is sometimes removed before a pump is sold.
Two quick rules that avoid the most common ordering mistakes:
- The port code is not the through-drive code. A code that reads “12” or “62” in the port position simply means side-facing ports — the pump can take a through drive, but whether it actually has one is decided by the separate N00/K../U.. position. Never assume.
- Series 32 couples flange, port plate and through drive together. K.. couplings come with flange C and port plate 12; the universal U.. comes with flanges D or U and port plates 22/32. The largest size (180 cm³/rev in Series 32) always uses the universal type. If you are not sure, send us the code and a photo of the rear — we will confirm.
2. Seal material: FKM or NBR — match your oil and temperature
The seal code sits right after the series and rotation letters. Modern pumps are almost always sealed with V = FKM (fluororubber), and this is the safe standard for replacement:
- FKM (V) — continuous operation up to roughly +110 °C measured at the drain port, cold start down to about −25 °C. Fully compatible with standard mineral (HLP-type) hydraulic oil.
- NBR, nitrile (older code P) — found on older builds and some market versions. Slightly better at very cold starts (about −40 °C) but tops out lower: roughly +85 °C continuous.
If your machine runs ordinary mineral hydraulic oil and normal temperatures, the FKM (V) version covers nearly every case — including machines that originally carried the older NBR seal. Flag it to us only if the machine runs in extreme cold or you know it was built with a special low-temperature seal.
One hard limit that no seal choice fixes: this pump family is designed for mineral oil per DIN 51524 and is not suitable for water-containing fire-resistant fluids (HFA/HFB/HFC-type emulsions and solutions). If the system uses a water-containing fluid, do not try to solve it by “upgrading” the seal — tell us the fluid type first.
3. Ports: what the working-port codes mean
3a. Working ports — what the type code says
In the type code, the working-port position describes the two large working ports. The official type-code table for Series 31 lists the working ports as “SAE flange connections according to ISO 6162, working ports metric” and “SAE flange connections according to ISO 6162, working ports UNC”, each with two arrangements:
- Metric fastening thread — code 11: ports to the rear (not for through drive); code 12: ports at top, at bottom, on the opposite side (for through drive). On sizes 71 and 88 the same two arrangements are coded 41 and 42.
- UNC fastening thread — code 61: rear (not for through drive); code 62: top/bottom/opposite side (for through drive). On sizes 71 and 88 they are coded 91 and 92.
- Series 32 — the type-code table lists “SAE flange ports” with a metric fastening thread: code 11 = rear (only without through drive “N00”); code 12 = at top, at bottom, on the opposite side.
3b. Port specifications are printed per size
One working port is the pressure port and the other is the suction port. On the size pages the datasheet lists, for every size, the flange standard, the thread and the maximum pressure of the working port, the suction port and the small ports (L, L1 drain ports and X pilot port). These details belong to your exact displacement, so send us the complete code from the nameplate and we check them on the size page for your pump.
3c. Drain and pilot ports in practice
In a standard installation one of the two drain ports (L or L1) is connected to the tank and the other is plugged, and the small X port is used for the external pilot pressure of remote-pressure and load-sensing controls — keep it connected exactly as the original machine had it.
Before you order: a 60-second checklist
- Is a second pump mounted at the back of the original, or was one removed? → The replacement must keep the same through-drive type (K.. or U..), not N00.
- What does the code say for the seal (V or P) and what oil/temperature does the machine run? → FKM (V) covers nearly everything with mineral oil.
- What are the port codes (metric or UNC: 11/12, 41/42, 61/62, 91/92)? → Quote them from the nameplate so we check the ports on the size page.
Not sure about any of the three? Send us a photo of the nameplate (full model code), a photo of the back of the pump showing whether a second pump is mounted, and tell us your hose/pipe thread type and hydraulic fluid. We will check the through-drive type, seal and port specification against your machine and confirm the right replacement before you order.
