How to Find Your Final Drive Part Number

A seller can only send the right final drive if you can say exactly which one is on your machine. Drives that look alike can differ in gear ratio, motor displacement, brake or port layout. A drive that bolts on can still run at a different speed from the other track, and the machine will not travel straight.

Start with the number on the tag. The machine’s serial number backs it up. When the tag is gone, photos and a few counts still give a seller something to work from.

Where is the part number on a final drive?

Look for a tag on the travel motor and on the gearbox. It is usually a metal plate, riveted or screwed on, or a printed label. On most excavators the two are built as one unit: the motor faces in, toward the middle of the machine, and the gearbox faces out and turns the sprocket.

Some drives carry one tag for the whole unit, and some carry one on each half. On many machines the motor sits behind a bolted guard over its hoses. Its tag may be out of sight until the guard is off.

Write down every number on every tag, and note which came from the motor and which from the gearbox. Photograph each tag square on and close enough to read, then take a wider shot that shows where it sits on the drive.

Which number on the tag is the part number?

No single line is always the part number, because layouts differ between makers. A tag can carry a model or type code, the unit’s own serial number, a date, and sometimes a ratio or a displacement.

Two kinds of number matter. One is the machine part number, the number the machine maker gives the drive in its parts book. The other is the drive or motor maker’s own model number. A tag may show either, or both, and each is useful to a seller. Send whatever is there.

Copy a motor’s model code in full, not only its first characters. On many motors the later characters record options such as a two-speed shift.

What if the tag is painted over or worn?

Whether it is painted over, worn or caked in mud, photograph the tag as you find it, before you clean anything. Then, once the drive has cooled, clean it gently with a rag. A wire wheel or a scraper can erase a stamped or etched plate, and a solvent or a pressure washer can lift a printed label.

Light often does more than scrubbing. A flashlight held low and almost flat to the plate shows stamped characters by their shadows, sometimes even under paint. Photograph the plate lit that way, from two or three angles.

Why does the machine’s serial number matter?

A model can change drives partway through production, and the serial number places your machine before or after the change. With it, the machine’s parts book, or the maker’s online parts lookup where you have access, shows the drive the machine was built with.

Take the make, the model and the serial number from the machine’s serial plate, which is a different plate from the drive’s tag. Where it sits varies by maker, and the operator’s manual usually shows it. Copy the model exactly, letters and dash numbers included, because a suffix can mark a different series. The makes and models we list are on the machines page.

Then compare the parts book with the tag. The parts book shows what the factory fitted, and the tag shows what is on the machine now. If they differ, the drive may have been replaced, or its number superseded by a newer one. Send both: the difference is information for the seller, not an error to correct.

How to identify a final drive with no tag

Without a tag, a seller works from the drive itself and the machine around it.

What to send	What it tells a seller
Clear photos of the drive from several sides	The drive’s family, from the shape of its castings and covers
Any tag, stamp or maker’s mark left on the motor	The motor’s maker, and sometimes its model
Sprocket bolts: the count, and the bolt circle through their centers	Whether your sprocket fits the hub
Frame mounting bolts: the count, and their bolt circle	Whether the drive bolts to your track frame
The pilot diameter, the machined ring that centers the drive in the frame	Whether it fits the bore in your track frame
Hydraulic ports: how many, and where they face	How the hoses connect, and whether there is a port for a two-speed shift
A two-speed travel switch in the cab, often marked with a rabbit and a turtle	Whether the motor has to be two-speed

Measuring is the fallback, not the first step. With the drive on the machine you can count bolts, photograph the ports and check the cab without opening anything. The pilot sits inside the frame and cannot be measured until the drive is off. A bolt circle taken with a tape across a dirty hub is an estimate.

There are no general figures to measure against, because none hold from one machine to the next. The old drive and the machine are the reference, and a rule of thumb is not a specification. Measurements confirm a match that the make, model and serial have already narrowed.

Taking a drive off, loosening a fitting, removing a plug or lifting the machine is work for a qualified technician following the machine’s service manual. A hydraulic line can hold pressure after shutdown, and a pinhole leak can inject oil through skin, so never feel for one with your hand. Gear oil in a drive that has been working is hot and can be under pressure.

What about pumps, cylinders and swing bearings?

The same order works for other parts. A main hydraulic pump or a cylinder usually carries its own tag: start there, then add the machine’s make, model and serial. A swing bearing with no readable number has its own measuring sheet on the swing bearings page.

Mistakes that send the wrong part

• Ordering by model alone. When a model was built with more than one drive, the model narrows the choice and the serial makes it. Without the serial, a seller has to guess or send you back to the machine.
• Mixing up the motor’s number and the gearbox’s. Send the motor’s number as the drive’s, and you may be matched to a motor alone. Say whether you need the complete drive, the motor or the gearbox. If you are not sure, read how to tell which half has failed.
• Reading a casting number as the part number. A number cast into the metal is usually a casting or pattern number. It identifies the raw casting, and one casting can end up in more than one finished drive, with a different ratio, motor or brake. Photograph it and label it as cast in, but it is the tag’s number you want.
• Copying one line of the tag. The line you picked may be the unit’s serial number, which no parts book lists. A photo of the whole tag removes the guess.

Sending it to a dealer

Put together the machine’s make, model and serial, your photos, and every number from the tags, each marked motor or gearbox. The request form takes a typed part number with the make and model, and other numbers fit in its comments. Photos can go in your reply when the dealer answers. You can also go straight to a dealer from the dealer finder, or email it all to contact@dyco.net.