Transmission and Driveline Systems
Transmission and Driveline Systems
This domain tests manual and automatic transmissions, clutches, dual-clutch and CVT units, transfer cases, propshafts, differentials, driveshafts and wheel bearings. Expect questions on oil specifications, adaptation resets, noise and vibration diagnosis.
Core rules
Use the specified fluid; mixing automatic transmission fluids can cause shift quality faults and internal damage. After transmission repair or fluid change, reset adaptations where required and carry out the specified learn procedure. For a dual-clutch transmission, clutch calibration and basic settings are part of the repair. Check propshaft phasing, balance and centre bearing condition; mark a propshaft before removal so it can be refitted in the same orientation. Inspect CV joint boots and test for clicking on full lock. Differential diagnosis includes backlash, preload, bearing noise and correct oil level; check breathers for blockage.
Worked example
A vibration at 60 to 80 km/h. Reasoning: check tyre balance and runout first, because they are common causes. If those are correct, inspect the propshaft for missing balance weights, a worn centre bearing or incorrect phasing. A vibration that appears under acceleration and disappears on overrun often points to an inner CV joint or tripod rather than a wheel balance issue.
Traps
- Mixing transmission fluids or using the wrong specification.
- Failing to reset adaptations after repair.
- Disturbing propshaft balance or phasing.
- Overfilling a differential or gearbox.
- Ignoring a blocked breather.