Replacing a Final Drive Motor: What Changes From One Machine to the Next
The sequence for pulling a final drive is broadly the same on every tracked machine, and we set it out in the excavator final drive removal and replacement guide. What changes between machines is the part that catches people out: how the drive is mounted, how much it weighs, what has to come off first and which variant your serial number takes. Here is what differs across the machine types we supply most often, and what each one means for a final drive motor replacement.
Removing the final drive motor on a Komatsu D51
A dozer final drive is a different job from an excavator one. The drive is a bolt-on module carrying the sprocket segments at the rear of the track frame, and on a D51 class machine the sprocket segments are usually unbolted before the drive itself, which reduces both the weight and the awkwardness of the lift. Expect the assembly to be heavier than the equivalent excavator unit and plan the lift accordingly.
Two points are specific to dozers. The track must be fully released and, on machines with sealed and lubricated track, the adjuster grease fitting has to be cracked carefully rather than opened fast. And the final drive housing on a dozer often shares oil with the sprocket hub bearing, so check the manual for the correct fill point and quantity before you refit. Getting the oil level wrong here is a common cause of a repeat failure.
Replacing a final drive motor on a Komatsu excavator
On PC-series excavators the drive comes out through the outside of the track frame once the hoses are marked, capped and released. Komatsu changed travel motor specifications several times within the same model designation, so the machine serial number decides which drive you need far more reliably than the model badge does. Our Komatsu final drive motors catalogue holds 441 part numbers for exactly this reason, and the casting number on the old motor is the fastest way to land on the right one.
New Holland mini excavators and the EH35 final drive motor
Compact machines look easier and often are not. The drive is lighter, but access is tight, the hoses are short, and there is rarely room to withdraw the unit without removing the track guard first. On a machine of this size it is worth dropping the track completely rather than trying to work around it.
Mini excavators also carry a small gear oil volume in a housing that runs hot, which is why they are unforgiving about maintenance intervals. Parts for these machines are listed under New Holland final drive motors.
Compact track loaders
Skid steers and CTLs load the travel circuit far harder than an excavator does, because steering is done by driving one track against the other. Drives come off from the outside with the machine safely supported, and both sides are often replaced together since they have done identical work. Caterpillar owners should start from our CAT skid steer final drive motors page, where the range is broken down machine by machine.
What to have ready before you start
Lifting equipment rated for the assembly, not improvised. Caps and plugs for every hose and port you will open, ready before the first connection comes apart. Labels or tape for the lines. The correct gear oil and the fill quantity from the manual. New mounting hardware if the old bolts have been on and off before, because stretched bolts do not hold torque. And the manufacturer's procedure for your specific machine, which overrides anything general you read online, including this page.
The mistakes that come back to us
Three of them account for most repeat failures. Hoses reconnected in the wrong order, which sends pressure where the case drain should be and destroys the new motor on the first movement. Track tension set by eye and left too tight, which loads the new bearing from the first hour. And skipping the flush after a failure that put metal into the circuit, which feeds the debris from the old drive straight into the new one. None of the three is expensive to avoid and all three are expensive to repeat.
The three things that decide whether the new motor survives
Identify the variant before ordering
Casting number on the motor, machine serial number, and a photo of the mounting flange. Send all three to our parts specialists and the match is checked against the manufacturer parts books rather than assumed.
Flush if there was metal
Debris left in the lines goes straight into the replacement. The procedure is in flushing before a final drive replacement.
Get the case drain and the torque right
Reconnect the case drain line clear and unrestricted, and torque the mounting and sprocket hardware to the figures on our bolt torque settings page.
Before you commit to a replacement
Confirm the drive is actually the fault, using the symptoms of a failing final drive, and check the economics in rebuild or replace a final drive motor. When you are ready, the full range for nearly 40 brands is in the final drive motors catalogue, new units, shipped across the contiguous United States and Canada, most dispatched the same day.
