Removing and installing a final drive: guide with line assignment

To avoid installation errors, we recommend having a specialist workshop fit the drive. If an installation error occurs, the warranty is void. Wherever possible, follow the machine manufacturer's installation instructions. The steps and notes below come from our daily work with final drives.

Before you start

• Final drives are heavy, 20 to 50 kg on mini excavators, several hundred kilos on larger excavators. Provide lifting gear and make sure the machine stands securely.
• Depressurise the hydraulic system and secure the machine against moving.
• Have plugs and caps ready for the open lines. Dirt in the hydraulic system harms the new drive.
• Compare bolt pattern, lines and speeds of the new drive with the old one beforehand.

Removing the old final drive

1. Remove the track. Release and remove the rubber track or split the steel track.
2. Remove the sprocket. Undo the bolts on the sprocket side and take off the sprocket.
3. Remove the cover plate. Unbolt the travel motor cover on the inner side of the track frame.
4. Mark the lines. Label every hydraulic line clearly, for example with coloured tape and a photo.
5. Remove and cap the lines. Protect all hoses and ports against dirt immediately.
6. Unbolt the drive. Undo the bolts on the machine frame from the inside and carefully lever out the drive.

Installing the new final drive

1. Pre-fill. Fill the travel motor chambers and the lines generously with hydraulic oil. The motor is then lubricated at start-up and little air remains in the system.
2. Clean the mating faces. Frame and drive must sit clean and flat against each other.
3. Bolt the drive. Tighten the bolts crosswise to the torque in the manufacturer's manual.
4. Connect the lines. According to the assignment below. Take special care, a wrong connection can destroy the travel motor immediately.
5. Fit sprocket and track. Tension the track according to the operator's manual.
6. Check gear oil. Check the oil level before the machine moves.
7. Test run. Drive slowly at low engine speed first, test both directions and both speeds, then check for leaks.

Assigning the hydraulic lines correctly

Final drives have 2, 3, 4 or 5 hydraulic lines with different pressures. The layout differs from manufacturer to manufacturer. On our final drives the ports are colour-marked:

Port	Marking	How to recognise it
Supply in and out	Green	Largest diameter, above 200 bar. If swapped, the machine only travels in the wrong direction.
Case drain	Blue	Small diameter, returns to the tank unpressurised
Second speed	Red	Small diameter, looks similar to the case drain. Located at the front, side or rear depending on the drive.

The case drain line

The case drain line returns oil that escapes inside the motor housing to the tank without pressure. If it is not connected, blocked or under pressure, pressure builds up in the motor housing. That destroys the shaft seal and can cause severe damage to the travel motor. The line must be connected correctly, clear and without significant back pressure.

Finding the second speed line reliably

Pilot line and case drain line look very similar. This is how to find the right one:

1. Mount the drive and connect the two supply lines.
2. Put the two similar hoses into a bucket.
3. Start the excavator at the lowest engine speed.
4. Operate the switch or lever for second speed.
5. The hose that now releases oil belongs on the second speed port (red).

Two-speed drive on a single-speed machine

If the mini excavator has three lines and only one speed, the second speed port remains unused. It must not be capped, though. Connect it to the case drain line with a T-piece or directly to the second case drain port, so no pressure can build up.

Help with the swap

Not sure about the assignment or the right drive? Call us or send a photo of the ports. Find the right final drive in the catalogue by brand, by machine weight on the page excavator final drives.