Hydraulic final drive motors are used in a variety of mobile equipment, such as mini and large excavators, to provide power to the tracks or wheels. These motors are typically used in place of a mechanical final drive, which uses gears to transmit power. Hydraulic final drive motors offer several advantages over mechanical systems, including improved efficiency, higher power-to-weight ratio, and better controllability.
In a hydraulic final drive system, power is transmitted from the engine to the hydraulic pump, which converts the mechanical energy into fluid pressure. The fluid is then sent through a system of tubes and hoses to the hydraulic motor, which converts the fluid pressure back into mechanical energy. The hydraulic motor is connected to the tracks or wheels of the vehicle, and it uses the mechanical energy to move the vehicle.
One of the main advantages of hydraulic final drive systems is their efficiency. Because the fluid in a hydraulic system is not subject to the same friction losses as gears, the system can transmit power with less energy loss. This means that the engine does not have to work as hard to produce the same amount of power, which can lead to improved fuel efficiency.
Hydraulic final drive motors are also lighter and more compact than their mechanical counterparts, making them a good choice for mobile equipment where weight is a concern. In addition, because the fluid in a hydraulic system is not subject to the same wear and tear as gears, hydraulic final drive systems require less maintenance than mechanical systems.
One of the main disadvantages of hydraulic final drive systems is their cost. The initial cost of a hydraulic system is typically higher than that of a mechanical system, and the components of a hydraulic system, such as the pump and motor, are also more expensive to repair or replace.
Another disadvantage of hydraulic final drive systems is their reliance on a supply of clean, uncontaminated hydraulic fluid. If the fluid becomes contaminated or runs low, it can cause the system to malfunction or fail. It is important to regularly check and maintain the hydraulic fluid to ensure that the system is operating properly.
Overall, hydraulic final drive motors offer several advantages over mechanical systems, including improved efficiency, higher power-to-weight ratio, and better controllability. While they may be more expensive to maintain, they can be a good choice for mobile equipment where weight and efficiency are important considerations.
Hydraulic final drive motors are an essential component in many heavy machinery and construction vehicles, providing the necessary torque and power to drive the vehicle's tracks or wheels. These motors are highly efficient and durable, making them suitable for use in a wide range of applications.
One of the main applications of hydraulic final drive motors is in earthmoving machinery, such as bulldozers, excavators, and backhoes. These vehicles rely on the power and torque provided by hydraulic final drive motors to move soil, rock, and other materials during construction projects. The motors are also used to power the vehicle's tracks or wheels, allowing it to move around the construction site.
In the construction industry, hydraulic final drive motors are used in a variety of applications, including grading, trenching, and digging. They are also used in the operation of attachments such as buckets, rippers, and hammers. The power and torque provided by these motors enables the machinery to perform a range of tasks, including breaking up concrete, digging foundations, and clearing debris.
Hydraulic final drive motors are also commonly used in agricultural machinery, such as tractors, combines, and harvesters. These vehicles require powerful motors to drive their wheels or tracks, allowing them to move through fields and perform various tasks, such as plowing, planting, and harvesting. In addition to driving the wheels or tracks, hydraulic final drive motors are also used to power the various attachments and implements used in agriculture, such as tillers, mowers, and spreaders.
Another application of hydraulic final drive motors is in material handling equipment, such as forklifts and cranes. These vehicles use hydraulic final drive motors to power their wheels or tracks, allowing them to move heavy loads around warehouses, construction sites, and other locations. In the case of forklifts, the hydraulic final drive motor is used to power the lift mechanism, enabling the vehicle to lift and move pallets, boxes, and other materials. In cranes, the hydraulic final drive motor is used to power the boom and other moving parts, allowing the vehicle to lift and move heavy loads over long distances.
In addition to these applications, hydraulic final drive motors are also used in a wide range of other industries, including mining, forestry, and military vehicles. In the mining industry, hydraulic final drive motors are used in a variety of vehicles and machinery, including dump trucks, loaders, and conveyors. In the forestry industry, they are used in logging equipment such as skidders and forwarders. And in the military, hydraulic final drive motors are used in a range of vehicles, including tanks, personnel carriers, and artillery.
There are several factors to consider when selecting a hydraulic final drive motor for a particular application. These include the size and weight of the vehicle or machinery, the required power and torque output, the operating environment, and the budget. It is important to choose a hydraulic final drive motor that is suitable for the specific application and meets the required performance specifications. Failing to do so can result in reduced efficiency and productivity, as well as increased maintenance costs and downtime.
In conclusion, hydraulic final drive motors are an essential component in many heavy machinery and construction vehicles, and are used in a wide range of applications. These motors provide the necessary power and torque to drive the vehicle's tracks or wheels, and are highly efficient and durable. It is important to choose a hydraulic final drive motor that is suitable for the specific application and meets the required performance specifications.
Every hydraulic motor does the same job in principle: it turns fluid pressure and flow into rotation and torque. What separates one type from another is how the fluid acts on the moving parts, and that decides the torque it can produce, the speed it can reach and the pressure it will survive. Among the hydraulic drives used on tracked heavy equipment, four designs cover almost everything you will meet.
Two meshing gears in a close-fitting housing. Fluid enters on one side, pushes the gear teeth around, and exits on the other. They are compact, cheap, tolerant of contamination and easy to service, which is why they run auxiliary functions, fan drives and small attachments. Their weakness is internal leakage past the gear tips, so efficiency drops as pressure rises. You will not find one driving a track.
A slotted rotor sits off-centre inside a housing, with vanes that slide out to seal against the wall. Pressure on the exposed vane area turns the rotor. Vane motors run smoothly and quietly at moderate pressure, and they suit steady, continuous duty. They do not like shock loading or the very high pressures a travel circuit sees, so on construction machines their use is limited.
This is the design that moves tracked machinery. Pistons sit in a cylinder block parallel to the output shaft and push against an angled swash plate. As each piston is pressurised it forces the block to rotate. Because several pistons are always under load, the design handles very high pressure and delivers high torque in a small package.
Two variants matter in practice:
The swash plate angle is set, so the motor gives one displacement, and speed follows flow directly. Simple, predictable and common on single-speed travel circuits.
The swash plate angle can be changed while the motor runs. Reducing the angle reduces displacement, which raises speed and lowers torque for the same flow. This is what a two-speed travel function actually is, and the mechanism is explained in detail in how the two-speed travel motor works.
Here the pistons are arranged around the shaft like spokes and push outward against a cam ring, or inward against an eccentric shaft. The geometry gives very high torque at very low speed, which is why radial designs appear in direct drive applications where a gearbox is not wanted. They are larger and heavier than an axial unit of equivalent output, which limits their use on compact machines.
Direct drive hydraulic motors turn the load straight off the motor shaft. They are mechanically simple, but to produce the torque a track needs they have to be physically large. The alternative is what almost every excavator and loader uses: a smaller, faster axial piston motor combined with a planetary reduction gearbox. The planetary set trades speed for torque, and the whole assembly fits inside the track frame. That combination is the final drive, and it is what people mean by a hydraulic final drive motor.
The motor shaft turns a central sun gear. Planet gears mounted in a carrier walk around it inside a fixed ring gear cut into the housing, and the carrier drives the sprocket hub. Two or three stages of this give reduction ratios high enough that a motor turning thousands of revolutions per minute moves a sprocket at walking pace with enormous torque. Because the load is shared across several planet gears at once, the arrangement carries far more torque than a single gear pair of the same size.
If you want to see how those components sit together and which of them wears first, the breakdown is in final drive motor parts and what wears first.
On a tracked excavator, skid steer, compact track loader or dozer, each track is driven by a final drive hydraulic motor: an axial piston unit paired with a planetary gearbox, usually with a spring-applied parking brake and often with two-speed shift. Mini excavators use the same architecture at smaller scale.
When one of them needs replacing, close to 40 equipment makes are covered in the final drive motors catalogue. Stock units usually go out the day you order, anywhere in the contiguous United States and Canada, and each listing states its own cover of up to two years. Main pumps for the same machines are under excavator hydraulic pumps. If you are unsure which variant your machine takes, send the casting number and serial to our parts specialists.
Assembling the hydraulic final drive motor can seem like a daunting task, but with the right tools and knowledge, it can be a relatively straightforward process. Here are the steps you'll need to follow to assemble the rotary components of your hydraulic final drive motor:
Assembling the rotary components of a hydraulic final drive motor can be a challenging task, but with careful attention to detail and the proper tools, it's certainly achievable. Just be sure to follow these steps and take your time, and you'll have a fully functional hydraulic final drive motor in no time.
We sell new final drives, so take the bias into account and check the numbers yourself. That said, the honest answer is that final drive repair makes sense in a narrow set of cases and loses money in most of the rest. Here is where the line actually sits.
Three situations genuinely favour repair. The first is a leak caught early: the gear oil is still clean, the only fault is a weeping duo-cone seal, and a seal kit plus fresh oil puts the machine back to work for a small fraction of a replacement. The second is an obsolete machine for which no new assembly is manufactured any more, where a rebuild is the only route. The third is a low-hour drive damaged by a single identifiable event, such as a case drain line that was left disconnected, where the rest of the assembly never ran contaminated.
If your drive fits one of those, rebuild it. The rest of this page is about the cases that do not.
Once a bearing or a gear starts shedding material, that debris circulates through the whole housing. The planetary set, the bearing races, the rotating group and the valve plate have all been through the same grit. A rebuild that replaces the obviously broken parts returns the rest to service with their remaining life already spent, which is why so many rebuilt hydraulic motors and rebuilt final drives come back within a year.
A piston motor rebuild lives or dies on the rotating group, which is matched and lapped to microns. Most shops that rebuild hydraulic motors do not remanufacture the cylinder block and valve plate, they reuse them, and the internal leakage that made the motor weak in the first place is still there when it goes back on the machine.
An excavator travel motor rebuild is usually quoted before the housing is opened. The bill after teardown depends on what the shop finds, and by then the machine is already down and there is little room left to negotiate.
A rebuild means removal, shipping to a shop, teardown, waiting on parts, reassembly and refitting. That is commonly one to three weeks. A new unit ships from stock and goes on as soon as it arrives. On a machine earning daily, the difference in downtime often exceeds the difference in parts price on its own.
Rebuild warranties are typically short and hour-limited, and they cover the parts that shop replaced rather than the assembly. A new drive from us carries coverage of up to two years, depending on the item, under our warranty policy.
Take the rebuild quote, add the shipping both ways, add an allowance for what teardown will find, then multiply your day rate by the realistic downtime. The same arithmetic applies when a shop quotes to rebuild a hydraulic motor or a pump drive. Compare that against a new unit shipped from stock with same-day dispatch. On mini excavator final drive rebuilds the two figures are often close, and the new unit wins on risk. On larger machines the rebuild can look cheaper on paper until the downtime is priced in. Our final drive motor replacement cost guide sets out what to compare.
A slow or dead track is not automatically a failed drive. The main pump, the two-speed solenoid, the travel circuit relief and the case drain can all produce the same symptom, and swapping a drive that was never at fault is the most expensive way to find that out. Work through the symptoms of a failing final drive first, and on a Caterpillar track loader follow the codes in the CAT 289D drive motor diagnosis guide. If you want to know which internal part matches which symptom, the breakdown is in final drive motor parts and what wears first.
Whatever killed the old drive is still in the machine. Flush the circuit before fitting, following the hydraulic flush procedure, check that the case drain line is clear and unrestricted, set track tension to specification rather than by eye, and torque the mounting hardware using our bolt torque settings. Then keep the gear oil on schedule using our final drive gear oil change guide.
The final drive motors catalogue lists new assemblies across some 40 machine makes, and anything held in stock normally leaves the same day. Send your model and serial number through the quote form and we will confirm the exact unit before you commit either way.
Hydraulic gearboxes, also known as hydrostatic transmission systems, are a type of mechanical system that uses pressurized fluid to transmit power from one location to another. They are commonly used in heavy machinery, such as bulldozers and excavators, as well as in a variety of industrial and manufacturing settings. Here are a few interesting facts about hydraulic gearboxes:
Overall, hydraulic gearboxes are an important and widely used type of mechanical system that have a number of unique characteristics and capabilities. They are highly efficient, versatile, and capable of transmitting power over long distances and generating high levels of torque, making them an ideal choice for a variety of applications.
Hydraulic final drive motors are an essential component of many types of heavy machinery, providing the power needed to move the machine's tracks or wheels. However, sometimes these motors can develop oil leaks, which can cause problems and reduce the efficiency of the machine.
There are several potential causes of oil leaks in hydraulic final drive motors. One common cause is a damaged seal. The seals in a hydraulic final drive motor are responsible for keeping the oil contained within the system and preventing leaks. If a seal becomes damaged or worn, it can allow oil to escape, causing a leak.
Another possible cause of oil leaks in hydraulic final drive motors is a crack in the motor housing. This can occur due to impact, corrosion, or other types of damage. If there is a crack in the housing, oil can escape and cause a leak.
A third potential cause of oil leaks in hydraulic final drive motors is a loose fitting. If a fitting is not tightened properly, it can allow oil to escape and cause a leak.
To fix an oil leak in a hydraulic final drive motor, you will need to locate the source of the leak and replace any damaged parts. This may require disassembling the motor to access the internal components. If you are not comfortable performing this type of repair yourself, it is recommended that you seek the assistance of a trained mechanic.
In addition to fixing the oil leak, it is also important to address any underlying issues that may have caused the leak in the first place. This could include replacing worn seals, repairing damaged housing, or tightening loose fittings.
Overall, fixing oil leaks in hydraulic final drive motors is an important part of maintaining your heavy machinery. By addressing these issues as soon as they arise, you can prevent further damage to the motor and ensure that your machine is operating efficiently.
There are several potential causes of noise in a hydraulic final drive motor. One common cause is a failure of the drive gear or sprocket. These components can become worn over time due to normal wear and tear, or they may be damaged by impact or overloading. If the drive gear or sprocket is failing, it can cause the motor to make a grinding or clicking noise.
Another possible cause of noise in a hydraulic final drive motor is contamination of the hydraulic fluid. If the fluid becomes dirty or contaminated, it can cause the motor to make a loud, irregular noise as it operates. This can be caused by a variety of factors, including debris getting into the fluid system, or the use of low-quality hydraulic fluid.
A third potential cause of noise in a hydraulic final drive motor is a problem with the motor itself. This could be due to a malfunctioning component within the motor, or it could be caused by an electrical issue. If you hear a loud, abnormal noise coming from your hydraulic final drive motor, it is important to diagnose the problem as soon as possible to prevent further damage to the motor and the machine.
To diagnose the cause of noise in a hydraulic final drive motor, you will need to first perform a visual inspection of the motor and the surrounding area. Look for any visible signs of damage or wear, such as cracks or missing parts. You should also check the hydraulic fluid level and condition, as well as the drive chain and other components.
If the visual inspection does not reveal the cause of the noise, you may need to perform additional tests to pinpoint the problem. This could include using a stethoscope to listen for specific sounds coming from the motor, or using diagnostic equipment to check for electrical issues.
In some cases, you may be able to fix the problem by replacing a damaged or worn component, or by cleaning or refilling the hydraulic fluid system. However, if the issue is more complex, it may be necessary to seek the assistance of a trained mechanic.
Overall, diagnosing and fixing noise issues with your hydraulic final drive motor is important to ensure that your heavy machinery is operating correctly and safely. By paying attention to any unusual sounds and taking the time to diagnose and repair the problem, you can prevent further damage to the motor and keep your machine running smoothly.
A final drive is two machines bolted together. On one end there is a hydraulic piston motor that turns oil pressure into rotation. On the other there is a planetary gearbox that trades that speed for torque. Between them sit the bearings and seals that decide how long the whole assembly lasts. Knowing which part is which turns a vague noise into a specific answer, and it tells you whether you are looking at a seal kit or a new unit.
Open a drain plug and the oil tells you most of what you need to know. Clean oil at the right level means the seal is holding. Grey, milky oil means water ingress and a failed face seal. Fine glitter suspended in the oil means bearing or gear material is already circulating. Chunks on the magnetic plug mean the planetary set has started to break up and the housing is now full of debris that will migrate into the motor.
Sound and behaviour narrow it further. A whine that rises with travel speed points to the motor. A growl under load with the machine loaded on one track points to bearings. A clunk on direction change points to gear backlash. Put together with the checks in the seven symptoms of a failing final drive, that is usually enough to decide before anything is pulled apart.
A duo-cone seal kit and fresh gear oil are worth doing the moment the oil looks wrong and nothing metallic has appeared yet. Caught at that point, the job is a few hours and a small parts bill. Our gear oil change guide covers the intervals that keep drives in that window.
Once metal is in the oil, the calculation changes, because the bearings, the gear set and the rotating group have all been through the same debris. What that means in money, and when a full replacement is genuinely the cheaper option, is worked through in rebuild or replace a final drive motor.
When a new assembly is the answer, Hydraulic America stocks units for nearly 40 equipment brands in the final drive motors catalogue, new, shipped across the US and Canada, with coverage of up to two years depending on the item.
If you’ve spent much time around people in the heavy equipment industry, you’ve probably heard a lot of different terms used to describe a final drive motor for an excavator. You’ve probably also heard a number of different terms used for a backfill blade, since it also gets called a dozer blade, and if you’re newer to the industry, you’ve likely been part of conversations that felt like they were taking place in a foreign language.
Heavy equipment can be like that. Here at Mini Final Drives, we regularly hear about a half a dozen different names for the final drives we sell. It doesn’t phase us, because we’ve been in the heavy machinery business for over 50 years, and we’re fluent in the language of excavators and other heavy machinery.
Whether you’re new to this space, or you’ve been in it for decades like we have, it can be helpful to know what others might call that thing you call a dipper. Here’s a glossary of sorts, in no particular order, and occasional further explanation about how some terms came about.
Final Drive Motor. As a complete unit, an excavator final drive motor provides the power to turn the tracks and move the excavator. Simply stated, it is composed of two primary components that are sealed and joined together – the first is the hydraulic “motor” that receives energy from the main hydraulic pump. The second part is the gearbox, which is called the “final drive,” because it is, as stated in the Google dictionary, “the last (final) part of the transmission system...”
The hydraulic motor is the part of your final drive motor to which the hydraulic hoses connect. Most people simply call this portion the “motor,” but terms like travel motor and propel motor, also appear in the industry. Interestingly, a lot of people mistakenly see the hoses on the back side of a final drive motor and think it is a hydraulic pump, but it is not. The central pump is located elsewhere on the excavator and supplies the hydraulic power to turn that final drive motor.
So what is the final drive? The final drive is the planetary gearbox that protrudes through the track sprocket and contains a couple gear oil fill/drain plugs (see our other articles about the importance of maintaining that gear oil!). In our experience, 90% of people in the heavy equipment industry simply use the term "final drive" to describe a final drive motor, but technically the "final drive" is only the gearbox portion, which would, of course, not work without the hydraulic motor to supply the rotational power. Due to the relatively high cost of parts and labor to join these two sections, mini and midi excavator final drives and travel motors are rarely sold separately because it isn't cost practical (unlike on much larger machines where it is more economical), so you will likely need to replace both portions with a complete, new, pre-assembled unit when either reach end of life.
Other slang terms for a final drive motor have cropped up in the industry, such as walking motor, track drive, and track motor. As they say, “a rose by any other name is still but a rose,” and that’s true for all the various terms you may have for a final drive motor and its components.
Grousers. Your excavator or dozer’s tracks need good traction in order to operate in most conditions. Grousers are the protruding portions on an excavator’s track that rise up like zipper teeth. They increase traction. They also sometimes get referred to as cleats, and if you’ve ever played soccer, football, baseball, or golf, you understand why.
Maximum Bucket Force. Also called maximum or max digging force, the maximum bucket force is the amount of force that can be utilized in digging with an excavator’s bucket. It should not be confused with the maximum crowd force, or breakout force, which refers to the excavator arm and the amount of force it’s able to use to “break out” the load.
The Boom and The Arm. The angled arm on your excavator is called the boom, and the piece that’s pinned to the boom is called the arm. Boom as a term, is pretty universal, except for knuckle booms, which can move to the right or left. The arm can also be referred to as the stick or the dipper. How far an excavator’s arm can extend is referred to as its reach.
Ground Clearance. Ground clearance refers to the space between the machine’s undercarriage and the ground, between the treads. If you’re operating a piece of heavy machinery, keeping your ground clearance in mind is an essential part of doing your job well, so you don’t get high-centered, stuck, and risk damaging your machine and losing time.
House. The house isn’t just the cab that sits on top of the undercarriage where the operator “lives.” When people in the heavy machinery industry refer to the house, they mean the cab, the fuel tank, counterweights, the hydraulic tank, and the engine.
Counterweights. Counterweights, depending on the age of the excavator you’re working with, can be made out of cast iron, lead, concrete, cast steel, you name it. They provide a “counterweight” to the load, balancing it and making it more stable, which also uses less energy and causes less stress for the machine.
Swamp pad. Also called a swamp mat and a wetland mat, a swamp pad is a large, usually wooden pad placed underneath the tracks on a dozer or excavator anytime the ground is soft, often from water. It works by spreading out the machine’s weight so the tracks don’t sink into the ground and get stuck. Rubber Duck. Known more often as a wheel excavator, a rubber duck is just an excavator that has wheels instead of tracks. The origin of the slang term rubber duck is disputed. Some say it refers only to the rubber wheels, while others claim it’s a reference to how the wheel excavator wobbles back and forth on certain ground conditions, kind of like a rubber duck in the bath.
At MiniFinalDrives, we don’t care what you call it, especially when it comes to final drives. If you call us and tell us you need a "track drive motor for a Kubota KX91-3 mini excavator", we know exactly what you mean and what you need, which is a complete final drive and travel motor for the Kubota KX91-3, fully assembled and ready to install! Just give us a call to chat - we’re always glad to help you find the right final drive motor solution to keep your machine moving! And if you have any questions about heavy equipment vocabulary, we’re glad to help out with that too.
Our family at Mini Final Drives has been providing excellent Quality, Value, and Service for over 50 years, and you can continue to count on us for a lifetime of friendly, helpful support for all your final drive and travel motor needs. Call us today at 877-483-2806 or visit our online store at www.minifinaldrives.com to find and order what you need today for Fast and Free delivery to your door.
