Every tracked excavator has two final drives, one at the back of each track frame. They are the parts that turn the sprockets and move the machine. They are also easy to order wrongly. This guide explains what a final drive is, where it sits, how it works, what oil it takes and what we need to identify the right replacement first time.
A final drive is the travel motor on an excavator. It bolts into the track frame at the sprocket end, takes hydraulic oil from the machine's control valve and turns the sprocket, which drives the track. To identify a replacement we need the mounting flange measurements, the bolt hole count and bolt size on both flanges, the machine type, model and serial number, and a clear photo of the tag plate. Terrapart final drives cover machines from 0.8 to 50 tonnes and are backed by up to a 24-month warranty.
What is a final drive on an excavator?
Final drive and travel motor are two names for the same part. Manufacturers, parts catalogues and fitters use both. Whichever name you use, it is the unit that converts hydraulic power into rotation at the sprocket.
The drive has two sides. On the motor side, hydraulic oil from the machine's control valve turns the motor. On the gearbox side, the unit turns the sprocket. The sprocket bolts directly on to the final drive, and its teeth engage with the links in the track chain or rubber track as the drive turns to give the machine motion. The gearbox side runs in gear oil and is separate from the hydraulic side.
Where is the final drive on an excavator?
The final drive sits inside the track frame behind the sprocket, bolted to the frame through its mounting flange. The sprocket bolts to the outer face of the drive and the hydraulic hoses enter from the inside of the frame.
The identification tag is usually mounted on the side of the drive facing inwards, the opposite side to where the sprocket is bolted. It often sits behind a teardrop-shaped cover plate held on by three bolts. Many drives carry two tags, one on the gearbox side and one on the motor side. A clear photo of the tag is the most useful thing you can send us.
How does an excavator final drive work?
The drive has three types of hydraulic port, and the fitting instructions supplied with every Terrapart drive colour code them.
- Green: main feed ports. These take the forward and reverse high-pressure hoses from the valve control. They are the two thickest hoses. Swapping them reverses the direction of travel.
- Red: second speed port. This carries the two-speed signal. The port has a fixed size and the supplied fitting should not be replaced.
- Blue: drain ports. Use the uppermost connection so that trapped air and high oil pressure can escape.
Move the travel lever and oil is directed to one of the green ports. The motor turns, the gearbox turns the sprocket and the track moves. Reverse the flow and the machine reverses. All Terrapart drives are two speed. The gearbox side carries its own gear oil, which is why the level needs checking after fitting.
Because the sprocket is bolted straight to the drive, the condition of the undercarriage feeds back into it. Sharp and worn sprockets can let the chain slip or jump through the teeth, and that shock loading damages the final drive motor. If your drive has failed, read the signs of failure in a final drive and check the rollers, idlers and sprockets before the new unit goes on.
What oil goes in an excavator final drive?
The gearbox side of the drive takes gear oil. After fitting a Terrapart drive, the instructions are to check the oil level in the final drive and top up with SAE 85W/90 or standard gear oil. The hydraulic side runs on the machine's hydraulic oil, and that oil matters just as much. If the previous drive failed, its hydraulic oil may be carrying metal particles. We strongly recommend a complete change of hydraulic oil and a new hydraulic filter whenever a final drive is changed.
Check the machine manufacturer's manual for the service interval and oil grade specified for your model, and follow the manual where it differs.
How do I identify the right final drive?
Most drives look alike from the outside, so we identify them by measurement and by the tag plate, not by eye. Our final drive check sheet asks for the following, and we send you the sheet with a marked-up drawing showing exactly where each measurement is taken.
| What we need | Detail |
|---|---|
| Frame mounting flange | The flange dimensions, taken across the flange that bolts to the track frame |
| Flange to sprocket | The distances from the mounting flange to the sprocket mounting face |
| Bolt holes | Number of holes and bolt size on both flanges |
| Machine details | Machine type, model and serial number |
| Speed | Whether the existing drive is single speed, yes or no |
| Tag plate photo | A clearly legible photo of the tag on the motor side of the drive |
One note on bolt holes: we are generally looking for equally spaced holes. If a flange has nine equally spaced holes plus one out of pattern, report it as nine equally spaced bolt holes. With that information our hydraulics team can confirm the correct unit and current availability. If a measurement is uncertain, send what you have with the tag photo and we will work through it with you.
Fitting a new final drive without losing the warranty
Every Terrapart final drive is supplied with a comprehensive fitting kit and detailed fitting instructions. The steps that protect the warranty are the ones most often skipped under time pressure.
- Check the hydraulic oil for metal particles from the previous failure. Drain enough oil to remove them, and change the oil and filter completely if in doubt.
- Clean the installation area, especially the hoses. Ingress of dirt causes early failure.
- Pipe it by the colour code. Green main feed, red second speed, blue drain. Incorrect piping will result in non-warranty failure.
- Single speed machines. All drives are two speed. On a single speed machine the red port is unused, so attach a hose from the free blue port to the red port to avoid pressure build-up. If you tell us the machine is single speed when you order, we make this modification before the unit leaves the warehouse.
- After fitting, check the gear oil level and top up with SAE 85W/90 or standard gear oil, run the excavator backwards and forwards at minimum revs, then attach a pressure gauge to the hydraulic circuit and confirm the pressure matches the machine manufacturer's specification.
Terrapart final drives suit machines from 0.8 to 50 tonnes and a wide range of tracked applications. Many units are manufactured by leading OEM suppliers including Eaton, Doosan, Nabtesco, Brevini and Trasmittal Bonfiglioli. Each drive is manufactured to OEM specification in ISO 9001 approved facilities, and thoroughly inspected and tested to ensure correct fitment and performance.
Drives are available from stock to fit machines from Bobcat, Case, Cat, Doosan, Hanix, Hitachi, Hyundai, IHI, JCB, Kobelco, Komatsu, Kubota, New Holland, Neuson, Sany, Takeuchi, Terex, Volvo and Yanmar. All final drives are backed by up to a 24-month warranty. Place your order prior to 4.30pm and it will be despatched for delivery on the next working day.
The rest of the Terrapart hydraulics range
Final drives
Travel motors for excavators and tracked equipment, supplied with a fitting kit and fitting instructions. Up to a 24-month warranty.
Hydraulic pumps
Hydraulic pumps, gear pumps and work pumps from manufacturers including Rexroth, Kawasaki and Mottrol. 12-month warranty.
Swing motors and reducers
Units from Kawasaki, Toshiba, Shibaura and Mottrol alongside manufacturers' own brands. 12-month warranty.
Our hydraulics team is available to assist with specification, fitment and technical queries on any part of the Terrapart hydraulics range.
Frequently asked questions
What is a final drive on an excavator?
A final drive is the travel motor that turns the sprocket on each side of an excavator. It has a hydraulic motor side, fed by the machine's control valve, and a gearbox side that turns the sprocket. The sprocket bolts directly to it.
Where is the final drive on an excavator?
At the sprocket end of each track frame. The drive sits inside the frame behind the sprocket, bolted through its mounting flange, with the hydraulic hoses entering from the inside. The identification tag is usually on the inward-facing side, opposite the sprocket, often behind a teardrop-shaped cover plate held on by three bolts.
What oil goes in an excavator final drive?
The gearbox side takes gear oil. After fitting a Terrapart drive, check the level and top up with SAE 85W/90 or standard gear oil. The hydraulic side runs on the machine's hydraulic oil, and we strongly recommend a complete change of hydraulic oil and a new filter whenever a final drive is replaced. Follow the machine manufacturer's manual where it specifies a grade or interval.
How do I identify which final drive I need?
Send us the frame mounting flange dimensions, the distances from the flange to the sprocket, the number of bolt holes and bolt size on both flanges, the machine type, model and serial number, whether the existing drive is single speed, and a clear photo of the tag plate on the motor side of the drive.
Can I fit a two speed final drive to a single speed machine?
Yes. All Terrapart drives are two speed. On a single speed machine the red second speed port is unused, so a hose is fitted from the free blue drain port to the red port to avoid pressure build-up. If you tell us the machine is single speed when you order, we make this modification before the drive leaves the warehouse.
Need to identify a final drive?
Ask for the check sheet, send it back with a photo of the tag plate, and our hydraulics team will confirm the right Terrapart drive and current availability.
Astrak Group develops and manufactures products intended to be compatible with machinery and equipment from various manufacturers. Unless indicated otherwise, Astrak Group has no relationship, commercial or otherwise, with the owners of the trademarks.
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