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How the machine is put together

Axles, gearbox, engine, cab. What the specification sheet is actually describing, and which choices you live with for the vehicle’s whole life.

8 articles

Truck axle configurations: what 4x2, 6x2, 6x4 and 8x4 meanThe first number counts wheel positions and the second the driven ones, so a 6x2 has three axles with one driven, while a 6x4 drives both rear axles.19 October 2026 · 4 sources
European truck cabs: day cabs, sleeper cabs and flat floorsA day cab has no bunk, a sleeper adds a berth and a long-haul sleeper has two berths and standing height; cab names do not translate between makers.12 October 2026 · 9 sources
Aerodynamic cabs and the EU length rulesDirective 96/53/EC caps an articulated vehicle at 16.50 m. Articles 8b and 9a let an aerodynamic cab or a rear device exceed it, on the condition that the extra length buys no load.25 September 2026 · 12 sources
kW, hp and Nm: how to read a truck's power figuresKilowatts and horsepower measure the same thing, power is torque times engine speed, and EU law sets a minimum of 5 kW per tonne for trucks.19 October 2026 · 23 sources
Automated manual transmissions in heavy trucksWhy almost every European heavy tractor now shifts itself, how an automated manual differs from a torque-converter automatic, and why the gearbox is now a CO2-certification component under EU law.8 October 2026 · 9 sources
Axle ratios and final drive: single reduction, hub reduction and portalWhat the 2.31 or 5.41 on a rear axle line counts, the five axle types Regulation (EU) 2017/2400 defines, and why the portal axle exists — for ground clearance or a low city bus floor.23 September 2026 · 10 sources
Turbocompound engines: how they work and what makers claimA turbocompound engine's second exhaust turbine returns energy to the crankshaft; on the Volvo D13 I-Save and Renault Trucks DE13 TC it shows up as torque.24 September 2026 · 10 sources
What is a retarder? Engine brakes and what UN R13 requiresA retarder slows a heavy vehicle on long descents without the friction brakes; UN R13 groups it with exhaust and engine brakes as endurance braking.1 October 2026 · 10 sources