Transmission, Steering, and Suspension
This domain covers how engine torque reaches the wheels, how the driver steers, and what carries the vehicle's weight and absorbs road shocks.
Transmission
- Clutch: single dry plate. Pedal free play is essential, or the release bearing rides the pressure plate. A slipping clutch lets revs rise without road speed; a dragging clutch crunches gears when stationary.
- Gearbox: sliding mesh, constant mesh and synchromesh; gear ratio = driven teeth ÷ driving teeth.
- Final drive and differential: the differential lets the outer wheel turn faster in a corner; a live axle houses both final drive and differential.
- Automatic: torque converter (fluid coupling with torque multiplication) or a CVT with belt and pulleys.
Steering and suspension
Rack and pinion is standard on cars, recirculating ball on heavier vehicles. Geometry: camber is the wheel tilt seen from the front, caster is the steering-axis tilt seen from the side (it gives self-centring), toe-in counteracts the wheels' tendency to splay. Suspension: leaf springs on load-carrying axles, coil springs with MacPherson struts on cars, telescopic shock absorbers control spring oscillation, and anti-roll bars limit body roll.
Worked example
Engine 3000 rpm, top gear 1:1, final drive 4:1, rolling circumference 1.8 m. Wheel speed = 3000 ÷ 4 = 750 rpm; road speed = 750 × 1.8 = 1350 m/min = 81 km/h. Multiply wheel rpm by distance per revolution, then convert minutes to hours.
Traps
Confusing camber with caster; treating the differential as a reduction gear only; forgetting that toe is measured in millimetres while camber and caster are in degrees; blaming the clutch for a noise actually made by a worn release bearing.