Condition monitoring is a health assessment technique worldwide accepted and very popular in many industries especially where there are rotating machines involved in the processes. These techniques may be relevant in environments where the prediction of a failure and the prevention and mitigation of its consequences increase the profit and safety of the facilities. The maintenance of underground mobile mining equipment is one of these scenarios. It has several problem areas: harsh environment, potential risks and distant location of workshops. When a machine breaks down, there are two ways to handle the repair. Either the equipment has to be repaired on site at the production area or taken to the workshop. The difficulties involved in moving this type of large equipment are substantial but it might be difficult or unsafe to repair the LHD on site (depending on where and why it fails). Therefore it is necessary to identify the critical components and monitor them properly in order to skip undesired shutdowns or stoppages. This paper describes the benefits of different CM techniques applied to a critical part of a LHD machine (the transmission) in order to detect the abnormal behavior if any, identify the fault and predict the degradation. These techniques will provide enough information to optimize the maintenance actions minimizing and mitigating the costly effects of unplanned actions.