Sundstrand and Sauer-Danfoss Pump Identification
Sundstrand hydrostatic pumps and motors are still working on machines built decades ago, which is exactly why identifying them is awkward. The brand has changed hands twice, the nameplates weather badly, and, most importantly, the model number alone is not enough to order a service part.
The one thing most people miss: on these units the same item number can have several different part numbers. Which one you need is decided by the date code on the nameplate, not by the model number. If you send us a model number without a date code, that is usually why we come back asking for a photograph.
Sundstrand, Sauer-Sundstrand, Sauer-Danfoss, Danfoss
All four names appear on this equipment, and they are the same product lineage. The Sundstrand hydrostatic business became Sauer-Sundstrand, then Sauer-Danfoss, and now sits within Danfoss Power Solutions. Service literature is published under whichever name applied at the time, so a Series 18 manual may say Danfoss while your pump says Sundstrand. The part numbering carried across.
Do not confuse this with Char-Lynn. Danfoss also owns the Char-Lynn orbital motor line, acquired from Eaton in 2021, but that is a completely separate product family with different numbering. If your unit is a low-speed high-torque wheel or auger motor rather than a hydrostatic piston pump, see the Char-Lynn decoder instead.
What is on the nameplate
Every unit carries a nameplate on the housing. It gives you four things, and you need all of them:
| Field | What it does |
|---|---|
| Model number | Identifies the unit, its configuration and options. This is what tells us the series and build. |
| Date code | Year and week of manufacture, written as two pairs, for example 88-04 meaning the fourth week of 1988. This selects the service part.
|
| Part number | The manufacturer number for the complete assembly as built. |
| Serial number | Unit-specific. Useful for tracing a warranty or a prior rebuild. |
Why the date code matters, with a real example
Take item 31 in the Series 18 service parts list. Units with a date code from 78-01 up to and including 88-03 take one part number. Units with a date code of 88-04 or newer take a different one. Same item, same position in the pump, same model number on the plate. Only the date code separates them.
That pattern repeats throughout these manuals. It is the single biggest cause of wrong parts being shipped for Sundstrand units.
If the nameplate is gone
Weathered and missing plates are common on machines this old. Send us photographs and these details and we can usually place the unit:
- Overall shape and whether it is a variable pump, a fixed motor, a variable motor or a tandem unit.
- Input shaft: diameter, keyed or splined, and the spline count.
- Mounting flange bolt pattern and bolt circle diameter.
- Port sizes and their arrangement, including the case drain position.
- Control type: manual lever, hydraulic displacement control, or an electric displacement control with a solenoid and connector.
- Any casting numbers on the housing and the end cap.
- The machine it came out of, and its year if you know it.
Series we carry parts for
- Series 15
- Series 18
- Series 20
- Series 22
- Series 24
- Series 42
- Series 90
- Seal kits
- All Sundstrand parts
A note on Series 90
Series 90 units are designated by function: PV for the variable displacement pump and MF for the fixed displacement motor. If you are chasing a performance problem rather than a part, the adjustments that matter are the charge pressure relief valve and the multi-function valve settings. Charge pressure must stay at its specified value under all driving and braking conditions, because the charge pump is what keeps positive pressure in the main loop, feeds the control system and makes up internal leakage. Low charge pressure damages the transmission.
What we can supply
| Part | Notes |
|---|---|
| Seal kits and shaft seals | By series and, where it applies, by date code. |
| Charge pumps and gaskets | Including charge pump relief components. |
| Shafts | Keyed and splined, by series. |
| Rotating group components | Quoted to order against your model and date code. |
| Controls | Hydraulic and electric displacement controls. |
Send the nameplate, not just the number
A clear photograph of the whole nameplate gets you the right part first time, because it carries the date code as well as the model. If the plate is unreadable, send photographs of the unit itself and tell us what machine it came out of.
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Frequently asked questions
How do I identify a Sundstrand hydraulic pump?
From the nameplate on the housing, which carries the model number, the date code, the manufacturer part number and the serial number. You need the model number and the date code together, because the date code often determines which version of a service part fits.
What is the date code on a Sundstrand pump?
The year and week of manufacture, shown as two pairs such as 88-04, meaning the fourth week of 1988. Service parts lists frequently give different part numbers for different date code ranges under the same item number.
Is Sauer-Danfoss the same as Sundstrand?
Yes, it is the same product lineage. The Sundstrand hydrostatic business became Sauer-Sundstrand, then Sauer-Danfoss, and now sits within Danfoss Power Solutions. Part numbering carried across the name changes.
How do I identify an old Sauer-Sundstrand pump with no nameplate?
Send photographs plus the shaft type and diameter, mounting flange bolt pattern, port sizes and case drain position, control type, any housing casting numbers, and the machine it came from. That is normally enough to place the series.
What does PV or MF mean on a Series 90 unit?
PV is the variable displacement pump and MF is the fixed displacement motor.