Many larger RVs and motorhomes use a pressurized hydraulic fluid system to move slide-outs, leveling jacks, and landing gear. They are relatively simple hydraulic systems. Most have a simple displacement pump and gearbox transmission, a machined manifold with solenoid-activated flow control valves, some safety switches, and a little PCB brain.
Note: As an RV engineer/tech, I am a jack-of-all-technical-trades. (It’s part of the job description.) I do some HVAC/R, some mechanics of materials, some thermodynamics, some plumbing, some electrical, some hydraulics, etc. But I wouldn’t call myself a Subject Matter Expert on hydraulics, so I’ll do my best to use accurate language.
The hydraulic fluid does all the work. The pump provides the pressure, but the fluid is what actually moves everything. Automatic transmission fluid (ATF) is a commonly recommended hydraulic fluid. In fact, I keep a gallon of Dexron III in my service vehicle.
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