Drive Shaft & Mounting Flange on A10V Pumps: Read the Code, Order the Right One
When you replace an A10V or A10VSO axial piston pump, two mechanical features decide whether the new pump actually fits your machine: the drive shaft (the splined end that couples to your motor or engine) and the mounting flange (the bolt pattern and pilot that locate the pump on the bell housing). Both are fixed at the factory and both are written into the pump’s model code. If either one is wrong, the pump will not mount — no matter how similar the rest of the code looks.
The short version
- Every pump carries two code letters that define the mechanical interface: one for the drive shaft, one for the mounting flange.
- The standard industrial build is a splined (involute) shaft with a 2-hole flange. Many machines in the field use exactly this combination.
- In the model code these two letters sit right after the seal letter. Read them before you order, not from the photo of a similar-looking pump.
Where the shaft and flange live in the model code
Take a typical code:
A10VSO 71 DFR1 /31 R -V S C 12 N00
After the seal letter V, the first letter is the drive shaft and the second is the mounting flange:
| Code position | Letter here | Meaning |
|---|---|---|
| Drive shaft (first letter after V) | S | Splined shaft, standard version |
| Mounting flange (second letter after V) | C | 2-hole flange, SAE pattern |
| Then… | 12 / N00 | Working ports / no through drive |
Newer and older model generations arrange the code slightly differently, but the principle is the same: two letters define the shaft and the flange. When in doubt, send us the full code from the nameplate.
Drive shaft types
The shaft is the power input from your prime mover, so it must match the coupling or splined hub already on your motor or engine.
| Code | Type | When it is used |
|---|---|---|
| S | Splined shaft, standard | The default on almost all pumps. Straight replacement for a standard splined unit. |
| R | Splined shaft, higher torque (same spline as S) | Where the drive needs more torque capacity. The spline geometry matches S, so a standard coupling fits, but do not substitute S where the machine was built with R. |
| U | Splined shaft, reduced diameter | One spline size smaller than S for the same displacement. Needs its own coupling size; suitability for through drive is limited. |
| W | Reduced diameter, higher torque (same spline as U) | The high-torque version of U, on machines that need it. |
Shaft size grows with pump size: roughly 3/4 in splines on the smallest sizes up to 1 3/4 in on the largest (140–180 cm³/rev class) units. Which variants exist (R, U, W) also depends on pump size — not every variant is available on every displacement.
Mounting flange types
The flange locates the pump on the bell housing. Two things must match: the pilot diameter (the centering register that fits into the housing bore) and the number and spacing of the bolt holes.
| Code | Type | Typical use |
|---|---|---|
| C | 2-hole flange, SAE pattern | Standard on most industrial A10V pumps |
| D | 4-hole flange, SAE pattern | Optional on larger sizes; also required with some electronic controls and for certain through-drive builds |
| A / B | Metric flange, 2-hole / 4-hole | Metric-pattern machines (common on European-built equipment) |
Pilot diameters increase stepwise with displacement — for example roughly 82 mm on the smallest size, 101.6 mm on the 28/45 class, 127 mm on the 71–100 class and 152.4 mm on the largest SAE-pattern units. A 2-hole flange and a 4-hole flange are not interchangeable, and SAE-pattern and metric-pattern pilots are not interchangeable either.
Which combinations are typical
- Standard industrial pump: splined shaft (S) + 2-hole flange (C). This is the combination found on the vast majority of machines.
- Metric-built machine: metric flange (A or B code) with the matching metric shaft option — keep the whole pump inside the same pattern family.
- High-torque drives: R or W shaft codes where the original specification called for them.
- Two pumps on one shaft: if your pump drives a second pump through its rear, the through-drive hub (the code after the ports) must be chosen for the attachment pump’s shaft and flange — another reason to quote the complete code.
Checklist before you order a replacement
- Copy the two code letters for shaft and flange from the nameplate — do not judge by eye or by photos.
- Confirm the displacement (size) matches. Pump sizes that share the same pilot diameter (for example the 28 and 45 class) are still different pumps with different shafts — the pilot is not enough to identify them.
- Match the bolt count: a 2-hole flange will not fit a 4-hole bell housing and vice versa.
- Match the shaft to your coupling: a standard (S) spline and a reduced (U) spline on the same size pump use different couplings.
- Be careful on the largest sizes (140 class): different generations of this pump family use different flange pilots. Never assume two “140” pumps are mechanically interchangeable — check the codes.
- If the pump had a through drive (a second pump bolted to its rear), include that code too — the replacement must carry the same through-drive hub option.
Not sure which shaft or flange your pump has?
Send us the model code from the nameplate — something like A10VSO 71 DFR1 /31 R -V S C 12 N00 — and we will confirm the exact shaft and flange combination and quote a drop-in replacement before you commit. Getting the code right the first time saves a return and downtime.
