TRADE OF HEAVY VEHICLE MECHANIC - eCollege

Module 4 – Unit 2 Gearbox
Table of Contents
1. Learning Outcome................................................................................................... 1
1.1 Key Learning Points.................................................................................. 1
2.0 Health And Safety............................................................................................... 2
3.0 Manual Transmission ......................................................................................... 3
3.1 Purpose of Manual Transmission............................................................ 3
3.2 Torque and Speed...................................................................................... 4
3.3 Front-Wheel Drive Layout....................................................................... 6
3.4 Rear-Wheel Drive Layout......................................................................... 7
4.0 Gearbox................................................................................................................ 8
4.1 Gearbox Operation ................................................................................... 8
4.2 Gearbox Layout ......................................................................................... 9
4.3 Transaxle Designs.................................................................................... 10
4.4 Gear Ratios ............................................................................................... 11
4.5 Compound Gear Trains.......................................................................... 12
4.6 Gear Selection .......................................................................................... 14
4.7 Baulk-Ring Synchromesh Unit .............................................................. 15
4.8 Transaxle Synchromesh Unit ................................................................. 17
4.9 Bearings ..................................................................................................... 18
4.10 Oil Seals & Gaskets ................................................................................. 18
4.11 Lubrication (splash feed) ........................................................................ 20
4.12 Lubrication (forced-feed)........................................................................ 21
4.13 Gearbox oil-leakage prevention............................................................. 21
5.0 Drive Shafts / Final Drive............................................................................... 23
5.1 Front-Wheel Drive Shafts (Cv Joints etc)............................................ 23
5.2 Front-Wheel Differentials ...................................................................... 24
5.3 Rear-Wheel Final Drive .......................................................................... 25
5.4 Rear-Wheel Drive Shafts ........................................................................ 26
5.5 Universal Joints ........................................................................................ 27
6.0 NCT Requirements........................................................................................... 28
Heavy Vehicle Mechanic Phase 2 Revision 1.0 September 2007