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SKM Motor Vehicle Mechanic Level 3 study materials
SKM Motor Vehicle Mechanic Level 3 study resources

SKM Motor Vehicle Mechanic Level 3: Power Transmission Systems

SKM Motor Vehicle Mechanic Level 3 · Work through your exam, one topic at a time.

All guide sections

Power Transmission Systems

What this domain tests

This domain covers clutches, manual gearboxes, automatic transmissions, CVTs, final drives, driveshafts and CV joints. The exam expects you to distinguish slip, drag, noise and ratio faults, and to use the correct fluid and adjustment procedure.

Core rules

  • A clutch that slips shows engine speed rising without road speed under load. Check pedal free play, hydraulic fluid level and for oil at the bell housing before condemning the clutch.
  • A clutch that drags is hard to select gears, especially first and reverse, with the pedal fully down. Check release travel, air in the hydraulic line and a distorted clutch disc.
  • Use only the specified ATF or CVT fluid. Most modern automatic transmissions are filled for life only under normal use, but the level is checked at a defined fluid temperature with the engine running and the selector cycled.
  • A stall test checks torque converter and engine power; do not hold it for more than five seconds and do not repeat until the fluid has cooled.
  • Inspect CV boots for splits and grease loss; a clicking noise on full lock points to an outer joint.
  • Mark the propshaft and flange before removal to preserve balance.

Worked example

A manual car slips when climbing at 3,000 rpm; the tachometer rises but road speed does not. The handbrake test in third gear does not stall the engine. Pedal free play is within specification and the fluid is full. Removing the inspection cover shows oil inside the bell housing from a failed crankshaft seal. The reasoning is that oil has contaminated the friction disc, so the repair is to replace the seal, clutch disc, pressure plate and release bearing, and to clean the flywheel. Replacing only the disc would allow the oil to ruin the new part.

Traps

Wrong ATF causes shift quality complaints and can damage the unit. Checking level at the wrong temperature gives a false reading. Reusing a dual-mass flywheel beyond its wear limit causes vibration. Do not diagnose a slip as an engine fault without the handbrake test.