Gearmotors: Inspection, maintenance and lubrication

What are gearmotors?

Gearmotors are mechanical devices composed of an electric motor connected to a gearbox (or reducer) that reduces the rotational speed of the output shaft.

This reduction in speed allows for an increase in the available torque at the system’s output, enabling the use of gearmotors in various applications, such as conveyor belts, industrial automation, agricultural equipment, among others.

Small gearmotor
Small gearmotor –
Source: Portal da Inspeção

Gearmotors can perform various forms of motion, from simple rotations to more intricate and precise movements. Additionally, the design aims for high efficiency and longevity, offering a wide range of configuration options, including reduction ratio, gear type, dimensions, power, and other factors, whose adaptations depend on the user’s requirements.

Basic components of gearmotors

Below is a detailed list of the main components of a gearmotor and their respective functions:

  • Main housing – responsible for housing all internal and external components of a gearmotor.
  • Drive motor – responsible for driving the reducer.
  • Gears – a fundamental element that can vary in size and shape. Gears can have different combinations of size and number of teeth, enabling the reduction of transmission speed and consequently the amplification of torque.
  • Bearings – components installed on input and output shafts that allow controlled movement between parts and provide support for loads.
  • Backstop brake – when present in the gearmotor, it prevents the asset from rotating in the opposite direction to the main rotation.

Basic structure of a parallel shaft gearbox

Basic structure of the parallel shaft gearbox – Source: Sew Eurodrive
  • Sealing elements – have the function of retaining lubricant within the system, as well as preventing the entry of external contaminants through the input and output shafts.
  • Fixing elements – secure the movable parts, installed in the housing’s monoblock.
  • Level sight glass – allows inspection of the lubricating oil level in the system.
  • Drain plug – component for draining lubricating oil during replacement.
  • Breather – allows air exchange between the equipment and the environment. It has the function of allowing internal pressure to escape and ambient air to enter the system. It is important to size it correctly to prevent contaminants from entering the system.
  • Lubricating oil – serves to reduce friction mainly between the gears and to help dissipate the heat generated by friction.
  • Identification plate – allows identification of some basic information about the gearmotor such as: Input rotation / Output rotation / Construction form / Mounting position / Type of lubricating oil / Quantity of lubricating oil.
Image of a gearmotor name plate – many technical information can be identified
Image of a gearmotor name plate – many technical information can be identified – Source:

Points of attention regarding maintenance and inspection

The maintenance and inspection stage in gearmotors is important and crucial, as good practices contribute to prolonging the asset’s lifespan. Additionally, proper care minimizes the risk of unplanned downtime and can detect early failures.

Watch the recording of the Inspection Portal’s live stream on the subject:

Maintenance in the gearmotor

When it comes to maintenance, an important stage is the assembly stage. Thus, it is essential to follow some recommendations to avoid major technical problems later on, including:

  • Mounting base – it is crucial to check the levelling of the support base that will receive the gear motors, ensuring that it is completely rigid. Additionally, it is essential to clean the area to prevent particles between the base and the asset.
  • Mounting elements – the fastening screws of the gear motor must be properly torqued (according to the manufacturer’s recommendations). Additionally, of course, the use of screws, nuts, and washers with the appropriate resistance class.
Breakage of the gearbox base due to over-tightening
Breakage of the gearbox base due to over-tightening – Source: Portal da Inspeção

ATTENTION: The housing of the gear motor is made of cast material, so it may break if the mounting elements are excessively tightened.

  • Alignment – it is essential to perform alignment between the gearmotor and the machine shaft to be driven. Misalignment can cause damage to sealing elements, bearings, and even gears. This situation, besides increasing vibration levels, can also result in increased energy consumption of the equipment.
  • Lubrication – in some cases, equipment has a small load of protective oil against corrosion that comes from the factory. But this oil is not a lubricant! Therefore, before starting operation, it is fundamental to drain it and then add the lubricant specified in the manufacturer’s manual.

Inspection in the gearmotor

Regarding inspection, it is crucial to establish a route for sensitive inspection, especially for gear motors with high criticality. However, in addition to the sensitive inspection route, it is recommended to use predictive techniques, such as oil analysis and vibration analysis, to assist in the effective monitoring of components and identify potential failures early on.

Read also: Sensitive Inspection Route: everything you need to know (

Regarding sensitive inspection, small technical inspections can be performed using the senses to identify non-conformities. Thus, within the checks performed by visual inspection are:

  • Oil level and whether there is leakage;
  • The external condition of the housing;
  • Mounting elements;
  • Cleaning
  • Temperature

Furthermore, Dynamox has an inspection routines module (DynaSens). With it, the data collected in the field becomes a precise and reliable source for assertive maintenance decisions. Learn more about it here.

Lubrication: what we should pay attention to

Lubrication in any equipment is a crucial aspect, and in gear motors, it is no different. Since the lubricant performs fundamental functions, such as reducing friction and assisting in the dissipation of heat generated during movement and contact of gears.

Here are the points of attention that the maintenance/lubrication team should have with gearmotors:

1 – Type of Lubricant – it is essential to follow the manufacturer’s recommendation. Therefore, any modification in lubrication should occur only after a thorough technical study.

2 – Correct lubricant level: checking the oil level at the beginning and during operation is especially important, ensuring that the oil quantity in the component is adequate.

Older assets had the dipstick type oil level indicator. In them, it is necessary to remove the dipstick to check the oil level, which allows possible contamination in the system. Fortunately, nowadays, there are more efficient alternatives (such as 3D level indicators) that do not expose the machine to contaminants.

Gearmotor with dipstick sight glas
Gearmotor with dipstick sight glass – Source: Portal da Inspeção

Other necessary precautions

3 – Breather – the breather must be installed and fixed correctly. Therefore, it is essential to ensure that it is positioned correctly, which may vary depending on the gear motor installation. Installing the breather in the wrong position can lead to increased internal pressure, causing damage to seals and, consequently, lubricating oil leaks.

Breather installed in the wrong position
Breather installed in the wrong position – Source: Inspection Portal

4 – Lubrication plan – it is important to have a lubrication plan and, therefore, check the oil level. Thus, it is also essential for this lubrication plan to establish an adequate inspection routine on the breathers to check their saturation level or identify any obstruction.

Gearmotors are, therefore, robust equipment that, when well cared for, can operate for long periods without major issues. However, for this to happen, it is essential to have an appropriate inspection and lubrication plan, a trained technical team, and also to use predictive maintenance techniques to assist in monitoring these assets.

Want to improve condition monitoring in your industry? Then, get to know Dynamox’s solution!

Text written in partnership with the Portal da Inspeção.