Manual Gearbox Laboratory

Read the lesson

1st gear

Ratio: 3.70 : 1
Input: 2,000 rpm
Output: 540 rpm
Torque: × 3.55
Road: ≈ 15 km/h

illustrative · 100× slower

Gear

Engaged

2,000 rpm

Try three different gears — to doPick gears on the shift pattern.
Press the clutch pedal — to doDrag the clutch slider and watch the plate lift.
Engage reverse — to doSelect R and watch the idler slide in.
Select a gear or shaft — to doClick any part to see what it does.

1st gear · 3.70 : 1

1st gear: two reductions in a row

The 1–2 collar slides back and locks the biggest mainshaft gear. Power goes down the constant-mesh pair, along the layshaft, up through the smallest layshaft gear into the big 1st gear, and through the collar into the mainshaft. The output turns slowly with lots of torque.

Power path

Ratio from tooth counts

34/20 × 37/17 = 3.70 : 1

× final drive 4.10 = 15.17 : 1 overall

Each pair: driven teeth ÷ driver teeth. Two pairs in a row multiply.

Live numbers · illustrative
Engine speed	2,000 rpm
Gearbox inputafter the clutch	2,000 rpm
Output shaft	540 rpm
Torque in → out	150 N·m → 533 N·m
Torque multiplication	× 3.55
Power in → out96% efficient	31 kW → 30 kW
Clutch heatslip losses	0.0 kW
Road speedfinal drive 4.1, 0.31 m tyre	≈ 15 km/h

Illustrative teaching gearbox: tooth counts, ratios, final drive, efficiencies, engine torque and the clutch characteristic are invented round numbers, not the data of any production gearbox. Shaft rotation is slowed 100× and the clutch plate lift is exaggerated so both are easy to see; the amber glow marks the parts carrying torque.