What Causes Gearbox Failures?

Industrial Gearboxes are an integral part of any Transmission system and their failure can be critical to the machines they run. Common signs that there may be something wrong with your Gearbox include vibration, a louder noise than normal, fluid leaking or oil contamination. Here are some of the most root causes of Gearbox failure...




Any sort of vibration can generate excessive force, increase stresses on component, and increases abrasion wear. The cause of most vibration is some form of misalignment or imbalance. Imbalance is the force created by a rotating body when its centre of mass is offset from its centre of rotation, where misalignment is the deviation from a common centreline during operation. These faults often cause broken teeth on Helical and Bevel Gears as well as scoring and spalling of shafts. Any number of your components could be behind this and most often you will have to dismantle your Gearbox to diagnose.


Improper Lubrication


One of the biggest causes of corrosion is improper lubrication, many internal failures on the Gears and Bearings will be caused by insufficient and interrupted lubrication to the drive train, so ensuring a regular supply of lubrication to all internal operating components is crucial. This is easier said than done however as lubricant selection is dependent on many factors including the gear type, load, type, speed, temperature, input power and reduction ratio. Unless you have a specialist in this field it is normally wise to consult the original equipment manufacturer. 




Pitting is a sign of corrosion and both micropitting and macropitting might affect the running of your gearbox and as above, will most often affect the Gears and Bearings. Macropitting occurs when the level of contact stress is too much for the material to handle. This will often result in the formation of small craters on the surface of the part and can be prevented by lessening loads or by using higher grade materials. Micropitting will most often occur through inadequate lubricant between two surfaces which have a lot of sliding action between them. This presents itself visibly as the surface of the parts will change to appear frosted or matte in tone. This is relatively easy to prevent if you have the right lubricant.




This is also a form of corrosion which will affect the Gears and Bearings. When two surfaces make repeated contact through an oscillating motion, fretting corrosion may occur if lubricant isn’t used. Another cause of Fretting Corrosion is a lack of rotation over a long period of time. Fretting Corrosion usually presents itself as a black or brownish rust on the nuts. Proper use of lubricant and reduction of non-rotation time will help prevent fretting corrosion.




Scuffing is a very severe type of adhesive wear which damages tooth surfaces on the gear, Visually you will see scoring marks on the gear teeth. The surface damage can be easpecially sever on soft gear teeth, but where you have hardened Gears you may see surface ripples on the operating faces. The root cause of scuffing is again, inadequate lubricant between the teeth which creates high temperatures thanks to friction.




Bending fatigue is often caused through running your gearbox at improper temperatures, or through heavy loading. The gear teeth can’t handle the amount of stress being put upon them and you’ll notice marks and cracks begin to appear where the teeth operate. To avoid this decrease your load or improve the strength of your gear.


If your gearbox has suffered damage or failure from any of the above faults then we may be able to help. Bronte Precision can provide bespoke Gears, Casings and Drive Shafts for your gearbox. We work from your drawings, photos or even a bag of broken parts to manufacture new parts. We work alongside many repair specialists and may be especially useful if your gearbox is an obsolete model or from a manufacturer no longer in business. Bronte Precision are ISO certified and deliver across the UK.