Excavator Hydraulic Motors: How the Swing and Travel Motors Work

An excavator hydraulic motor is a part that turns oil pressure into rotating movement. A working excavator carries two kinds of them: one swing motor, which turns the upper body left and right, and two travel motors, one inside each track, which drive the machine forward and back. If something on an excavator spins rather than pushes, a hydraulic motor is doing it.

This is the simplest way to hold the whole machine in your head. The cylinders push and pull, so they move the boom, the arm and the bucket. The motors spin, so they turn the house and drive the tracks. Same pump, same oil, two different jobs.

The reason a buyer should care is money. The travel motor and the gearbox bolted to it, together called the final drive, sit at the bottom of the machine in mud and water all day, and they are among the costlier repairs an owner meets. Most of those repairs come from neglect rather than bad luck, which means they are avoidable. This guide explains what each motor does, what the numbers on the spec sheet mean, and what to listen for before you hand over money.

What is a hydraulic motor on an excavator?

A hydraulic motor is a pump running backwards. In a pump, the engine turns a shaft and the shaft pushes oil out under pressure. In a motor, pressurised oil is forced in, and that pressure turns the shaft. The same axial piston design is used for both, which is why spec sheets describe the motors on these machines as “axial piston motors”.

Everything starts at the engine. On the SANY SY220C-9XL Sparc+, a 148 HP (110 kW) engine drives two variable displacement axial piston pumps that together push up to 2 x 234 litres of oil per minute. That oil goes to whichever part the operator has asked for. Pull a joystick and it goes to the boom cylinders. Turn the house and it goes to the swing motor. Push the foot pedals or the travel levers and it goes to the two travel motors.

The joysticks and foot pedals are simply the way the operator tells the oil where to go. The excavator components guide covers the rest of the machine these motors sit inside.

One term worth clearing up early: displacement means how much oil a motor swallows per turn of its shaft. A motor with larger displacement turns more slowly but with more twisting force. Smaller displacement means faster and weaker. A two-speed travel motor, which most machines above the mini class use, changes its own displacement on the move. That is how a machine gets both a slow, strong crawling gear for climbing and a faster gear for crossing a site.

What does the swing motor do?

The swing motor turns the upper body of the machine on the ring bearing below it. It is a hydraulic motor with a reduction gearbox on its output, and a small pinion gear at the bottom of that gearbox meshes into the teeth cut around the slewing ring. When oil drives the motor, the pinion walks around the ring teeth and the whole house rotates.

Two details on the swing motor matter in daily work.

The first is the swing holding brake. This is a spring-applied brake inside the motor that locks the house whenever the operator lets go of the joystick. Without it, a machine parked across a slope would slowly turn under its own weight. The SY220C-9XL lists its swing motor as “1 Axial Piston Motor with Swing Holding Brake” in its own specification. If a machine you are inspecting creeps round on a slope after the operator releases the controls, that brake is worn, and it is a real fault rather than a quirk.

The second is that swinging is harder work than it looks. A loaded boom out in front is a long lever, and starting and stopping that mass thousands of times a day is what wears both the motor and the ring teeth. Operators call it ghumana, and the ones who do it smoothly get years more out of the swing system than the ones who slam the joystick from stop to stop.

Bigger machines sometimes carry more than one. The 84 tonne Tata Hitachi ZAXIS 890LCH lists two swing motors rather than one, because a single motor of a sensible size cannot turn that much mass.

What do the travel motors and final drives do?

The travel motors move the machine. There are two, one per track, each mounted at the rear of its track frame and driving the toothed sprocket that pulls the chain around. Because there is one motor per side, an excavator steers the way a tank does: run both the same way to go straight, run one side only to turn, run the two sides in opposite directions to spin on the spot.

The final drive is the travel motor plus the planetary gearbox bolted to it. The motor spins fast and weakly; the gearbox turns that into slow and strong. This is the assembly people mean when they say a machine “needs a final drive”, and it explains why the repair is expensive: the motor and gearbox are usually replaced or rebuilt as one unit.

Final drives fail for reasons that are easy to list and easy to prevent:

• Oil that is never checked. Each final drive holds its own small quantity of gear oil, separate from the main hydraulic tank. It is checked rarely because it is inconvenient to reach, and a gearbox run low on oil does not complain until the damage is done.
• Water and mud getting past the seals. This is the common one on Indian sites. Machines standing in canal work, monsoon slush or pond digging spend hours with the final drives underwater. Once a seal goes, the gear oil turns milky and the bearings are on borrowed time.
• Over-tight tracks. A track tensioned too hard loads the sprocket, and that load goes straight into the final drive bearings. Track tension belongs to undercarriage care, but the final drive pays the bill.
• Travelling long distances on the road. Tracked machines are built to work, not to commute. Long moves under their own power heat the final drives badly, which is a large part of why crawler machines are trailered between sites.

The good news for an owner is that draining a small quantity of gear oil and looking at it costs almost nothing. If it comes out milky or grey instead of clean oil, water is getting in, and catching that early is the difference between a seal and a full unit.

How much pressure and speed do these motors run at?

Travel circuits run at higher pressure than swing circuits on almost every machine, because moving a whole machine uphill needs more force than turning its top half. The table below is taken from the listed specifications of machines available in India, from a 7.5 tonne mini up to an 84 tonne mining class.

Specifications as per the current Aug 2026 listings. Three things in that table are worth reading properly.

Travel speed barely changes with machine size. The 7.5 tonne mini and the 84 tonne mining machine both top out around 4.6 to 5 km/h, which is a fast walk. An excavator is not a machine that travels, and a buyer who expects one to move around a spread-out site quickly has bought the wrong machine.

Tracking force rises steeply with weight. Maximum tracking force is the pulling effort the tracks can produce, and it climbs from 184 kN on the 21 tonne XCMG XE215i to 560 kN on the 84 tonne machine. That is what lets a heavy machine drag itself out of soft ground it has sunk into.

Gradeability is 35 degrees on all of the larger machines listed. That figure is the steepest slope the travel motors can climb, and it is a limit for the machine in good condition on firm ground, not a target to aim at on a wet bund.

Pressure is quoted in megapascals (MPa). Travel circuits on the larger machines here run between 34.3 and 34.8 MPa, against swing circuits that sit lower. On the Tata Hitachi NX 80, at ₹29.5–32.6 Lakh (indicative, as of Aug 2026), the travel circuit runs 27.5 MPa against a 23 MPa swing circuit. On the SY220C-9XL Sparc+ at ₹52.3–57.8 Lakh (indicative, as of Aug 2026), it is 34.3 MPa travel against 25.5 MPa swing. The ZAXIS 890LCH is listed at price on request.

The hoses feeding those circuits have to be rated for the same pressures, which is why a replacement is chosen by circuit and not by machine. Dash sizes, pressure ratings and fitting types are covered in the guide to excavator hydraulic hose sizes and fittings.

The pressure figures those motors work against, together with the main pump flow that feeds them, are set out by size class in the guide to excavator hydraulic pressure and pump flow.

What are the signs a swing motor or final drive is failing?

Both failures announce themselves through sound and behaviour long before the machine stops. Learning the four below is worth more than any inspection checklist.

• The machine pulls to one side when travelling straight. With both levers pushed equally, one track is turning slower. That is a weak travel motor or a worn final drive on that side, and it is the clearest single symptom there is.
• Whining or grinding from a track frame that changes with travel speed. Gearbox noise follows the sprocket. A noise that rises and falls with track speed is coming from the final drive, not the engine.
• The house drifts after the joystick is centred. The swing holding brake is worn or the motor is leaking internally past its own pistons.
• Swing is slow or weak in one direction only. Even swing speed both ways is normal. Strong one way and lazy the other points at the motor or its control valve rather than at the ring.

An internal leak is the failure people find hardest to picture, so it is worth a sentence. As a motor wears, oil starts slipping past the pistons inside it instead of pushing them round. The pump is still delivering, the gauge may look fine, but less of that oil turns into movement. The machine feels tired rather than broken, and it burns more fuel doing the same work because the engine is still driving the pump at full effort.

Any of these is a reason to look at the oil itself. The hydraulic system maintenance guide covers oil condition and filter changes for the main circuit, and the excavator oil capacity guide lists what the systems on these machines actually hold.

How do you make hydraulic motors last in Indian conditions?

Clean oil and sensible operating habits do almost all of the work. Nothing here is expensive; the cost is remembering to do it.

Keep water out. Where machines work in water, canal desilting, pond digging, monsoon foundation work, the final drive seals are the weak point. Wash the mud off the track frames at the end of a wet day rather than letting it set, and check the final drive oil more often through the monsoon than in the dry months.

Do not park the machine turned on a slope. Leaving the house swung across a gradient rests the whole weight of the upper body against the swing brake overnight, every night. Park square and the brake gets a rest.

Travel with the idlers leading where you can. Running with the final drives at the front on rough ground puts every rock straight into the gearbox housings. Keeping them at the rear lets the idler wheels take the hits first.

Trailer the machine between sites. Long road moves under the machine’s own power are the single most avoidable cause of final drive heat damage, and at 5 km/h they waste a working day as well.

Train the operator on smooth swings. A slammed joystick loads the motor, the gearbox and the ring teeth all at once. Operators who ease into and out of a turn are worth paying for, and the difference shows up in the undercarriage and swing system years later.

If you are working out what a machine costs to keep running rather than to buy, the equipment finance options we list are worth reading alongside the running costs, because the monthly outgo and the repair bills come from the same pocket.

What should you check on a used excavator?

On a second-hand machine the hydraulic motors deserve a specific test, because a seller can hide a weak final drive for one short demonstration and cannot hide it for twenty minutes.

Ask for these four, in this order:

• Travel it straight for at least 50 metres on level ground. Watch whether it holds a line. A pull to one side that appears only after the oil warms up is a motor that is leaking internally.
• Spin it on the spot both ways. Both directions should feel the same.
• Swing a full circle slowly, then stop and watch. Listen for knocking at the ends of the arc, and check that the house stays put when the joystick is released.
• Drain a little final drive oil from each side. Clean oil is fine. Milky or grey oil means water, and grey grit on the magnetic plug means the gears are already wearing.

A seller who refuses the oil check is telling you the answer. The used excavator buying guide covers the rest of the inspection.

If the machine checks out, compare it against what a new one costs before you commit. Browse the range of excavators, narrow it to the 15 to 25 tonne bracket most Indian contractors end up in, and speak to a dealer about the models that fit your work. The excavator guide hub carries the rest of this series.

How fast those travel motors actually move the machine is listed by size class, high range and low range, in our guide to excavator travel speed.

Prices, specifications and features are indicative, vary by variant, location and date, and should always be confirmed with the official OEM or authorised dealer before any purchase decision. DesiMachines is not liable for decisions taken on the basis of information that may have changed after publication. Specifications are taken from our listings at the time of writing.