How do I change my final drive?

Installation Guide

How to change a final drive

Step-by-step instructions for excavator travel motor installation

Mechanics
Hydraulic connections
Warranty checklist

Step-by-step instructions showing how to remove and install a final drive on an excavator

Replacing the final drive (also known as the travel motor or track drive) on a crawler excavator is a standard maintenance task, but it requires high precision and strict adherence to hydraulic safety procedures. Because these planetary gearboxes operate under massive hydraulic pressures (often exceeding 300 bar), incorrect hose connections or failing to clean the hydraulic circuit can lead to catastrophic motor failure within minutes of installation.

Important Warranty Safeguard! Do not replace a final drive without diagnosing and fixing the root cause of the previous motor’s failure. If the old motor suffered mechanical disintegration (piston wear, bearing fragments), metal particles are trapped in the return lines, case drain, and hydraulic reservoir. Installing a new travel motor without flushing the system and changing the filters will immediately destroy the new unit and void your manufacturer warranty.

In need of a replacement travel motor? Find a matching final drive for 2,000+ excavator models →

Pre-Installation Checklist: Protect Your New Travel Motor

Before installing your new final drive, complete these vital diagnostic and cleaning steps to ensure a safe installation:

1. Transit & Damage Inspection

Unpack the new travel motor and inspect it for physical damage that may have occurred during shipping. Verify that the shipping plugs in the ports are intact and have not leaked storage oil.

2. External Contamination Clean

Ensure the motor flange and the mounting surfaces inside the excavator track frame are completely clean of mud, rust, and debris. Any grit between the flanges can cause misalignment or bolt loosening.

3. Replace Hydraulic Filters

Replace the main hydraulic return filter, the case drain inline filter, and the pilot filter. This is the single most critical step in preventing cross-contamination from the failed old motor.

4. Flush Hydraulic Lines

Flush the travel hoses (main feed lines and the case drain line) with clean hydraulic oil before connecting them. If you suspect severe contamination, the entire hydraulic reservoir must be drained and cleaned.

5. Gear Oil Level Verify

Most final drives are shipped empty or with minimal storage oil. Place the drive on a level surface, remove the top fill plug, and fill the planetary gearbox with heavy gear oil (API GL-5 SAE 80W-90) until it overflows from the middle level plug.

Step-by-Step Guide: How to Remove & Install a Final Drive

Follow these structured steps to safely swap your excavator travel motor:

Raise and Secure the Machine

Position the excavator on flat, solid ground. Rotate the upper structure 90 degrees to point the boom over the side. Lower the boom and bucket arm to lift the target track frame off the ground. Place heavy-duty jack stands or wood blocks securely under the track frame. Stop the engine and lock out the hydraulic controls.

De-tension and Remove the Track

Locate the track adjustment valve behind the track frame cover plate. Loosen the grease valve slowly (do not back it out completely!) to release the grease pressure in the tension cylinder. Use a crowbar or step on the track to compress the idler wheel. Slip the rubber track or steel track link off the sprocket and slide it to the side.

Label and Disconnect Hydraulic Hoses

Clean the area around the hydraulic cover plate on the inside of the track frame. Remove the cover plate to expose the hoses. Mark each hose clearly (A & B for two main supply lines, C for the case drain line, and D for the 2-speed pilot line if present) using tape or color tags. Loosen the fittings, disconnect the hoses, and plug them immediately with plastic cap plugs to prevent oil loss and dust entry.

Unbolt and Remove the Old Final Drive

Support the travel motor’s weight using a hoist, crane, or forklift strap. Remove the sprocket bolts to take off the drive sprocket (often easier when the drive is still mounted, or you can remove sprocket and motor together). Remove the high-tensile mounting bolts that secure the motor housing to the track frame flange. Carefully pull the heavy assembly out of the track frame.

Install the New Final Drive Motor

Align the new travel motor assembly into the track frame mounting opening. Apply a medium thread locker (like Loctite 243) to the mounting bolts and insert them. Torque the bolts in a star pattern to the manufacturer’s recommended torque specifications. Mount the sprocket onto the hub, using thread locker and torque specs for the sprocket bolts.

Reconnect Hoses Labeled and Check Ports

Remove the shipping plugs from the new motor’s ports. Compare port sizes and layouts. Connect the main hoses A and B to the main flow ports. Locate the case drain port (always at the top point of the motor housing) and connect the case drain line C. If your motor has a 2-speed port, connect line D. Tighten all fittings to proper torque.

Mount Track, Bleed System, and Test

Mount the rubber or steel track back onto the sprocket and idler. Tighten the grease valve and pump grease into the tension cylinder until the track sag meets manufacturer specifications. Start the engine and run it at low idle. Keep the track suspended and slowly engage the track in one direction for 5 minutes. This purges air from the lines and ensures the motor body fills with hydraulic fluid, preventing dry friction damage. Check for leaks and lower the machine.

Piston Air Bleeding Warning:
Always execute the low idle test run for at least 5 minutes before driving the machine. Moving a newly installed final drive immediately under high throttle or full load will trap air pockets inside the motor pistons. Without hydraulic fluid present to lubricate, the pistons will score, leading to internal bypassing, loss of tracking power, and instant component wear.

Excavator Final Drive Replacement: FAQs

Can I reuse the old hydraulic oil and filters when installing a new final drive?

No. Worn or failed final drives release fine metal debris into the hydraulic system. Installing a new drive without replacing the hydraulic return filters, case drain filter, and flushing the lines will contaminate the new motor, leading to immediate wear and voiding the manufacturer’s warranty.

Where does the case drain line connect on a new final drive?

The case drain line must be connected to the designated drain port (usually the smallest port, labeled “D” or “Dr”). This line returns bypass oil directly to the hydraulic tank under zero pressure. Connecting a high-pressure line to the case drain port will instantly blow out the main shaft seal of the new travel motor.

What kind of oil goes into a final drive gearbox, and how much?

Crawler excavator planetary gearboxes require heavy gear oil, typically API GL-5 SAE 80W-90 or SAE 90. Mini-excavators (1 to 8 tons) usually take between 0.5 to 2.0 liters of gear oil. Do not fill the planetary gearbox with hydraulic fluid, as it cannot handle the heavy gear loads.

How do I ensure the hydraulic hoses are connected to the correct ports?

Before disconnecting the old travel motor, label each hose (A and B for main travel, C/Dr for case drain, and 2-Speed pilot if equipped). Compare the ports on your old motor with the ports on the new motor’s manual, as port positions can differ on aftermarket replacement drives.

Why is it recommended to run the new track motor at low idle first?

Running the travel motor at low idle (with the track suspended) for 5 minutes purges trapped air from the hydraulic lines and fills the motor block with hydraulic oil. Operating a new motor under full load with air pockets inside causes dry friction, piston scoring, and permanent internal damage.

Related Technical Guides & Internal Link Building

To avoid premature track motor failure, check out our guide on how to maintain a final drive correctly, including gear oil change frequencies. If you notice tracking speed issues, read our diagnostic article on excavator speed differences. Learn how to verify physical fitment before purchasing a replacement by reading our guide on how to measure a final drive correctly.

To understand the indicators of an motor in poor condition, see 5 signs your final drive is in bad condition. You can also learn more about our logistics by exploring our hydraulic spare parts inventory overview. For a full list of tutorials and excavator maintenance articles, browse the Mecatra blog overview.

For support, replacement quotes, or technical questions, fill out the form below or contact our expert team in Horsens, Denmark at info@mecatra.com.

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