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View Unit : Overhauling Gearbox Assemblies

Unit Reference Number
Qualification Framework
Overhauling Gearbox Assemblies
Unit Level
Level 3
Unit Sub Level
Guided Learning Hours
Unit Credit Value
Date of Withdrawal
4.1 Engineering
Unit Grading Structure
Assessment Guidance

This unit must be assessed in a work environment and must be assessed in accordance with the ‘Common Requirements for National Vocational Qualifications (NVQ) in the QCF’ which can be downloaded from Semta’s website: http://www.semta.org.uk/training_providers__awarding/national_occupational_standard/qca_assessment_requirements.aspx

Additional assessment requirements have been published by Semta. These additional assessment requirements are set down in Semta’s Mechanical Manufacturing Engineering Suite 3 unit assessment strategy which can be downloaded from Semta’s website: http://www.semta.org.uk/training_providers__awarding/national_occupational_standard/qca_assessment_requirements.aspx

Learning Outcomes and Assessment Criteria
Learning Outcome - The learner will:Assessment Criterion - The learner can:

1a. Overhaul gearbox assemblies


Work safely at all times, complying with health and safety and other relevant regulations and guidelines


Carry out all of the following during the overhaul of the gearbox assembly:

• obtain and use the appropriate documentation for the overhauling activities (such as job instructions, drawings, manuals)

• adhere to procedures or systems in place for risk assessment, COSHH, personal protective equipment and other relevant safety regulations and procedures to realise a safe system of work

• provide and maintain safe access and working arrangements for the work area

• ensure that the gearbox unit is suitably supported, and that appropriate lifting and handling equipment is available

• carry out the overhauling activities, following good practice/approved procedures

• ensure that components and surrounding structures are maintained free from damage and foreign objects

• return all tools and equipment to the correct location on completion of the activities

• leave the work area in a clean and safe condition on ...


... completion of the activities


Follow the relevant overhauling schedules to carry out the required work


Establish the components to be removed and, where appropriate, mark components to aid re-assembly


Ensure that any stored energy or substances are released safely and correctly


Carry out the overhaul to the agreed level, using the correct tools and techniques


Overhaul two of the following types of gearbox:

• crash mesh/sliding mesh

• variable speed

• constant mesh

• speed reduction/increase

• synchromesh

• differential

• planetary

• compound


Overhaul gearboxes operating on two of the following types of gear drive:

• spur gear

• helical gear

• crossed helical

• rack and pinion

• worm and worm wheel

• bevel

• spiroid (spiral bevel)

• hypoid

• harmonic drive

• combined drive (such as bevel and helical)

• other specific type


Carry out all of the following activities on the equipment being overhauled:

• cleaning parts prior to dismantling

• pre-disassembly checks and tests

• releasing stored energy (where applicable)

• draining/removing any remaining fluids

• dismantling equipment to unit/sub-assembly level

• dismantling units to component level

• removing and replacing components having interference fits (such as by expansion, contraction, pressure)

• proof-marking/labelling of components to aid reassembly

• checking components for wear and serviceability (such as visual, measurement, use of probes/scopes)

• replacing all damaged or defective sub-assemblies and components

• replacing all ‘lifed’ items (such as seals, bearings, gaskets)

• reassembling the gearbox unit

• balancing components (where applicable)

• ‘blue bedding’ ...


... components (where applicable)

• making mechanical connections

• setting and adjusting replaced components

• tightening fastenings to the required torque

• applying gaskets and sealant/adhesives

• applying correct lubrication during assembly

• securing components using mechanical fasteners and threaded devices (such as nuts, bolts, circlips, pins)

• applying locking and retaining devices (such as circlips, pins, wire locking, lock nuts, stiff nuts, swage nuts)

• applying protection to openings to prevent entry of contaminating debris


1b. Overhaul gearbox assemblies (continued)


Replace/refit a range of gearbox assembly components, to include eight of the following:

• gear housings

• bearings

• drive shafts

• lay shafts

• locks and stops

• gears/gear/trains/gear sub-assemblies

• static seals/gaskets

• dynamic seals

• sensors (such as oil level, temperature)

• oil filters

• level indicators

• oil pumps

• shims and packing

• levers and linkages

• selector mechanisms

• locking devices

• wire thread inserts

• pipes and unions

• mechanical controls (such as plungers, springs, rollers)

• electrical controls (such as solenoids, motors, switches

• other specific components


Carry out checks and tests on the overhauled gear box, to include all of the following:

• visual inspection for completeness of all operations

• visual inspection for freedom from damage or foreign objects

• applying protection to openings to prevent entry of contaminating debris

• carrying out any ‘special-to-type’ checks (such as bearing end float, gear backlash)


Overhaul gearbox assemblies, in compliance with one of the following:

• BS, ISO or BSEN standards and procedures

• customer standards and requirements

• company standards and procedures

• gearbox manufacturer’s requirements


Ensure that all removed components are correctly identified and stored in the correct location


Report any instances where the overhauling activities cannot be fully met, or where there are identified

defects outside the planned overhauling schedule


Complete the relevant documentation, in accordance with organisational requirements


Complete paperwork which includes one of the following, and pass it to the appropriate people:

• job cards

• computer records

• gearbox assembly overhaul logs or documents

• work authorisation documents


Dispose of unwanted components, waste materials and substances, in accordance with safe working practices and approved procedures


Deal promptly and effectively with problems within their control and report those that cannot be solved


2a. Know how to overhaul gearbox assemblies


Describe the specific safety practices and procedures that they need to observe when overhauling gearbox assemblies (including any specific legislation, regulations/codes of practice for the activities, equipment or materials)


Describe the health and safety requirements of the area in which the overhauling activity is to take place, and the responsibility these requirements place on them


Describe the hazards associated with overhauling gearbox assemblies (such as handling oils, greases, stored energy/pressure/force; use of power tools, misuse of tools, using damaged or badly maintained tools and equipment, not following laid-down overhauling procedures, lifting and moving large and heavy components), and how to minimise them and reduce any risks


Describe the importance of wearing protective clothing and other appropriate safety equipment during the overhaul


Explain how to obtain and interpret drawings, specifications, manufacturers’ manuals, history/maintenance reports, and other documents needed in the overhauling process


Explain how to carry out currency/issue checks on the specifications they are working with


Describe the quality control procedures to be followed during the overhauling operations


Describe the procedure for obtaining replacement parts, materials and other consumables necessary for the overhaul


Describe the company policy on the repair/replacement of components during the overhauling process


Describe the terminology used in gearbox assemblies


Describe the basic principles of how the gearbox assembly functions, its operating sequence, the working purpose of individual units/components and how they interact


Describe the extent to which the equipment is to be dismantled for overhaul


Describe the sequence to be adopted for the dismantling/reassembling of the gearbox assembly


Describe the techniques used to dismantle the gearbox assembly, without damage to the components or surrounding structure (such as release of energy/pressures/force; making mechanical disconnections; proof-marking components to aid reassembly; removing assemblies having interference fits (such as expansion, contraction, and the use of presses and extractors); removing mechanical locking and securing mechanisms/devices); and the need to protect the system integrity by ensuring that exposed components are correctly covered/protected


Explain how to lift and move large components and assemblies; the methods and equipment used to transport, handle and lift the components during the overhauling activities


2b. Know how to overhaul gearbox assemblies (continued)


Explain the need to ensure that lifting and handling equipment is within its current certification dates


Describe the methods of checking that components are fit for purpose, how to identify defects and wear characteristics, and the need to replace ‘lifed’ items (such as seals and gaskets)


Describe the uses of measuring equipment (such as micrometers, Verniers, expansion indicators and other measuring devices)


Describe the methods of reassembling the gearbox, using new or previously overhauled components (such as replacing assemblies requiring pressure/force, ensuring correct orientation, bedding in bearings and components, replacing mechanical locking and securing mechanisms/devices, torque setting components)


Explain how to make adjustments to replaced components/assemblies to ensure that they function correctly (such as checking alignment, balancing of rotating components such as torque converters, setting working clearance, setting travel, setting backlash in gears and pre-loading bearings)


Describe the various mechanical fasteners that are used, and their method of removal and replacement (including bolts, nuts, rivets, threaded fasteners, special securing devices)


Describe the various types of electrical connector that are used, methods of unlocking, orientation indicators, and locating and locking in of the connections


Describe the tools and equipment used in the overhauling activities, and how to check that they are in a safe/usable condition


Describe the importance of ensuring that all tools are used correctly and within their permitted operating range


Describe the importance of ensuring that all tools, equipment and components are accounted for and returned to their correct location on completion of the overhauling activities


Describe the procedure for the safe disposal of waste materials


Explain the need to complete the overhaul documentation and/or reports following the overhauling activity


Describe the problems that can occur during the overhauling activity, and how they can be overcome


Describe the extent of their own authority and to whom they should report if they have a problem that they cannot resolve

Equivalent Units
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