Kubota KX040-4 Final Drive Oil: Type, Capacity and Change Interval

If you are servicing a KX040-4, the oil in its travel-drive gear cases is a separate service item from engine oil and hydraulic oil. Searching for “KX040 oil capacity” without naming the compartment can bring back a perfectly accurate number for the wrong part of the excavator.

The KX040-4 operator's manual cited here specifies SAE 90 gear oil and approximately 0.65 litre (0.17 US gallon) per drive unit. Its first change is at 50 hours, then every 500 hours or at least annually. Check the edition applicable to your machine before treating those figures as a purchase list.

The KX040-4 figures, with their scope

Source: Kubota KX040-4 operator's manual, printed page 78, code RD158-8121-3, English US/Canada edition. This is the document behind the figures, not a claim that every later revision or related excavator uses them.

Is 0.65 litre for one side or both?

It is per unit. Two units at that stated approximate amount give a planning total of 1.30 litres. That arithmetic helps you avoid buying only enough oil for one side; it is not an instruction to pour a measured amount into each case regardless of the level check.

Allow for the practicalities of filling and the pack sizes available, but keep the distinction clear: the amount you buy, the nominal capacity and the correct final level are three different things. Record the oil actually used without treating every small difference from the approximate figure as proof of a fault.

Which plug sets the level?

The manual's procedure positions the drain plug at the bottom before the machine is shut down. After draining and refitting that plug, it describes filling through the oil-check port until oil flows out. Follow the illustration and the shutdown instructions on that page, including lowering the attachments, stopping the engine and removing the key.

Identify the drain, check and fill labels in the actual diagram before loosening anything. A plug near the top of a housing is not permission to fill the case to the top. Nor should a diagram for another final drive be used to guess the positions on yours.

The illustration below explains the idea of a level reference. It is deliberately not a plug-location drawing for the KX040-4; use the manufacturer's drawing for the actual arrangement.

Can another Kubota excavator use the same amount?

Do not assume it can. The KX080-3S operator's manual, printed page 69, gives approximately 1.35 litres per drive unit and an initial change at 100 hours, followed by 500 hours or at least annually. It also lists SAE 90.

That comparison is useful because even the same oil grade does not make the capacities and initial intervals interchangeable. A note on a workshop shelf saying “Kubota final drives — first change 100 hours” would be wrong for the KX040-4 edition used above.

Keep the model suffix in your service record. “KX040-4” is more useful than “Kubota mini,” especially when someone else will order the next supplies.

Can I use the hydraulic oil already in the workshop?

Do not choose oil merely because the container says Kubota. The manufacturer's oils and lubricants range includes separate engine, gear and transmission/hydraulic products. A brand name does not make those products interchangeable.

Use the specification in the applicable drive-unit procedure. If a supplier proposes a multigrade or another current product in place of the manual's stated grade, ask for confirmation that it is appropriate for your machine and conditions. This article does not establish an alternative viscosity, API category or product approval that the cited page does not provide.

A useful record for the next change

Record each side separately: date, machine hours, oil product and anything unusual observed during service. If one side has a leak or a markedly different drained amount, keeping left and right separate makes that information useful to the technician.

For a used excavator, an invoice saying “oil service” does not establish that both drive units were serviced. Ask which compartments were included. If the history is unknown, keep it marked unknown until the relevant work has been confirmed or carried out.

Do not postpone an annual task simply because the excavator has worked few hours. Conversely, completing a drive-oil change does not resolve a travel fault, unusual noise or damaged sealing; those need their own assessment.

Documentation for maintenance and further diagnosis

Use the operator's manual for the routine oil-change procedure. If a service reveals a leak or a travel problem, Byte Market's KX040-4 workshop manual listing includes maintenance information and travel-motor coverage. Check the listed model and document code before purchasing, then use the relevant procedure for the work being planned.