News · Mikołaj Skubina · 18.03.2026
Gear unit noise and geared motor vibration are among the most common warning signals in the operation of industrial drives. Not every unusual sound immediately means a serious failure, but ignoring the first symptoms very often leads to bearing damage, a deterioration in the condition of the gear teeth, higher operating temperatures and an unplanned line shutdown. In practice, a quick response gives the greatest chance of limiting repair costs and shortening downtime. NORD indicates that with increased noise and vibration, the mounting, coupling, frequency inverter parameters, system resonance and the condition of the motor bearings should be checked, among other things.
NORD drives are used in many demanding industrial applications, from intralogistics and conveyors to mixers, packaging systems and the food industry. This means they often operate under high loads, variable speeds, dust or elevated humidity. In such conditions, correct fault diagnosis of the technical condition is crucial. SPEC SERWIS, as an authorised NORD partner, carries out, among other things, geared motor condition assessments, component replacement, thermal imaging and endoscopic inspections, as well as drive checks and repairs, and also supports customers in selecting parts and contacting the manufacturer.
Which drive sounds should cause concern
A correctly operating geared motor is not completely silent. There is always a certain level of sound resulting from the operation of the gear teeth, the motor and the ventilation. The problem begins when the sound changes noticeably, intensifies or appears suddenly after a period of stable operation.
The most worrying sounds are metallic noises, scraping, whining, grinding, periodic knocking and speed-dependent sounds. In practice, particular attention should be paid to a situation in which the drive starts running louder than usual under an unchanged load. Such a symptom often indicates a deterioration in lubrication conditions, play, a bearing problem or progressive wear of the rolling elements.
With unusual sounds, check the frequency inverter parameters, the fan and the fan cowl, as well as the condition of the motor bearings. The manufacturer also suggests separating the motor from the gear unit in order to narrow down the source of the problem and determine whether the noise comes from the motor section or from the gear unit itself.
It is worth remembering that worn bearings often give symptoms gradually. SKF states that damage such as spalling and flaking of raceways develops over time and reveals itself precisely through increasing noise and rising vibration.
The most common causes of gear unit noise
Drive noise does not have to mean one specific failure. It is usually the result of one of several typical operational problems, or a combination of them.
The most common causes include:
- improper lubrication or deteriorating oil quality,
- bearing wear,
- excessive drive load,
- coupling misalignment,
- mounting play,
- system resonance,
- damage to the fan or fan cowl,
- contamination inside the system.
NORD explicitly states that with increased noise, the quantity and condition of the oil should be checked, along with the gear unit mounting, the influence of resonance and any overloading of the application that may lead to damage to the bearings or gear teeth.
The issue of seals and the cleanliness of the grease or oil is also very important. SKF emphasises that solid and liquid contaminants can damage the working surfaces of bearings, reduce lubricating properties and lead to higher temperatures, noise and vibration. This applies both to external contamination and to residues from an earlier failure that were not thoroughly removed during a repair.
From the perspective of a production plant, this means one thing: the sound itself is a symptom, but not a diagnosis. It is necessary to establish whether the source is the bearing, the gear teeth, the motor, the coupling, the mounting or the operating conditions of the entire system.
Drive vibration – what it means in practice
Geared motor vibration is one of the most valuable indicators of a drive's technical condition. It often appears before a failure that is visible to the naked eye. Well-managed observation of the vibration trend makes it possible to detect a problem before seizure, component fracture or a production stoppage occurs.
In practice, vibration can indicate imbalance, looseness, misalignment, resonance or wear of rotating components. Fluke points out that vibration analysis helps diagnose the most common problems of rotating machines, namely imbalance, looseness, misalignment and wear.
The vibration frequency says a lot about where the problem originates. High-frequency vibration may point to the motor or the input shaft, while other bands and characteristics may suggest trouble with the gear unit, the coupling or the application itself. The manufacturer also recommends checking the foundation, the mounting, the coupling and the frequency inverter parameters.
In everyday maintenance practice, one principle is important: vibration is not assessed solely "by ear" or "by touch". An operator's initial observation is valuable, but only measurement makes it possible to compare results, observe trends and make data-based service decisions.
How to check the condition of bearings in a geared motor
Assessing the condition of the bearings should start with operational symptoms, but it must not end there. A sequence of simple and logical steps is needed.
First, it is worth comparing the current level of noise and vibration with the machine's previous behaviour. If the drive ran stably and now whining, pulsation, rattling or increased vibration under load has appeared, this is a strong signal for further fault diagnosis.
The next step is a temperature check. A rise in the temperature of the housing, bearing covers or the areas around the shafts may indicate deteriorating lubrication, overloading or developing bearing damage. SKF indicates that contamination and a deterioration in the properties of the lubricant can simultaneously raise temperature, noise and vibration levels.
Then the mounting conditions should be checked. An overly loose ring fit, a worn seat, incorrect preload or a fitting problem can in themselves generate noise and accelerate wear. SKF states that improper seating and a lack of correct bearing clamping increase noise and vibration and worsen the operation of the entire system.
If the system allows it, it is worth separating the motor from the gear unit. NORD recommends such a step in order to narrow down the source of the problem. It is a simple way to establish whether the damage concerns the motor bearings, the input section of the gear unit or the reduction stage itself.
Drive fault diagnosis methods in a production plant
Modern drive fault diagnosis does not rely on a single method. The best results come from combining several techniques, because each shows a different part of the picture.
The foundation is vibration analysis. It is a particularly useful tool where drives operate continuously and are critical to the process. Fluke emphasises that effective fault diagnosis requires not only the measurement itself, but also knowledge of what to measure and how to interpret the results.
The second method is thermography. A thermal imaging camera helps detect overheating bearing zones, motor ventilation problems, overloading or abnormal operating conditions. SPEC SERWIS materials show that such inspection is part of the services delivered at the customer's site.
The third method is endoscopic inspection. It allows selected spaces and components to be assessed without full disassembly. This is particularly important when stopping the line is costly and a decision must first be made as to whether the drive qualifies for a quick repair or a planned overhaul.
In practice, fault diagnosis in a plant should also include an assessment of:
- the drive mounting and foundation,
- alignment,
- the condition of the coupling,
- the frequency inverter parameters,
- the oil level and condition,
- the influence of the application on resonance and overloads.
This approach is consistent with NORD's recommendations concerning increased vibration and unusual noise.
When geared motor servicing is necessary
Servicing should not begin only when the drive stops working. In practice, the moment for intervention comes much earlier.
A drive should be reported for service when the noise clearly intensifies, vibration increases over time, the operating temperature deviates from the norm for the given application, or traces of leakage and oil contamination appear. An equally important signal is recurring problems shortly after an earlier repair. This often means that the effect was removed, but not the cause.
NORD recommends a service consultation in the event of unusual sounds, strong vibration, temperature problems or a change in the drive's operating conditions. SPEC SERWIS has direct access to original NORD parts, service experience in line with the manufacturer's standards and the ability to carry out an inspection, a preliminary repair assessment, component replacement and on-site fault diagnosis.
This is precisely why, with symptoms such as gear unit noise, geared motor vibration or a suspicion of worn bearing symptoms, the most sensible course is a quick check of the drive and confirmation of the cause before a larger failure occurs. When replacing wearing parts, it is also worth opting for components of confirmed quality and compatibility. A good complement to this topic is our article on original spare parts and replacement parts, which helps explain how the choice of parts affects the durability of the entire drive.
FAQs
Below you will find answers to the questions that most often arise when diagnosing NORD drives in production plants.
Does every geared motor noise mean damaged bearings?
No. Noise can also result from a problem with the fan, the cowl, the coupling, the mounting, resonance, the oil condition or overloading of the application. Worn bearings are a common cause, but not the only one.
How can bearing noise be distinguished from gear unit noise?
Measurement-based fault diagnosis is most often needed. Observing the character of the sound, the vibration level, the temperature and the behaviour of the drive after disconnecting the motor from the gear unit helps. NORD recommends such separation in order to determine the source of the problem more precisely.
Does an increase in vibration always mean a failure?
Not always, but it always means a change in the machine's operating condition. Vibration can indicate imbalance, looseness, misalignment, resonance or wear. If its level increases over time, the drive requires checking.
What most often accelerates bearing wear in a drive?
Common causes include contamination, improper lubrication, incorrect fits, overly loose mounting, overloading and inadequate sealing. SKF indicates that such conditions translate into increased noise, temperature and vibration.
When must a drive be stopped immediately?
When there is a sudden increase in noise, strong vibration, a rapid rise in temperature, metallic scraping, pronounced mechanical play or symptoms indicating the possibility of further damage to the gear teeth or bearings. In such situations, continued operation can significantly increase repair costs.
Can SPEC SERWIS help with such fault diagnosis?
Yes. SPEC SERWIS supports customers in assessing the condition of NORD geared motors, on-site fault diagnosis, component verification, selecting the right parts and contacting NORD. The range of services includes, among other things, inspections, repairs, component replacement and thermal imaging and endoscopic inspection.