Automotive glossary starting with letter T


The tachometer is essentially a gauge that can display an engine's revolutions per minute (rpm or revs).


The TELEAID is a Mercedes-Benz optional feature based on a built-in telephone. Essentially, it can emit an automatic distress call to alert emergency services in the case of an accident. Depending on the type of accident or vehicle, the system can be triggered by the crash sensors which usually activate the airbags and/or belt tensioning devices or by the rollover sensor.

Three-valve technology

Some car manufacturers (mostly Mercedes-Benz in recent years) have dispensed with one of the exhaust valves in their large V6 or V8 DOHC engines in order to reduce the heat loss from the exhaust, thus helping the catalytic converter to reach its operating temperature sooner and improve the engines' emissions.

Tire Pressure Monitoring

Tire Pressure Monitoring (TPM) systems were developed as a safety measure, and are using wheel mounted sensors to continuously check all tires for any changes in pressure and informing the driver via a display on the dashboard or instrument panel.

Tire Pressure Monitoring Systems

A comfortable system for tire pressure monitoring detects even small pressure fluctuations, locates the affected tires and informs the driver with warnings of varying urgency.

Tongue Weight

The tongue weight is the actual force that is pressing down on the front axle of a vehicle and is strictly related to mass distribution between the axles.


Torque (also called couple) is a vector that measures the amount of rotational effort exerted at the crankshaft by an engine. The unit of measure is a pound-foot in the US and UK (and other Imperial system using countries), and Newton meter by metric system standards (specifically Europe).

Torsion Bar

The torsion bar is a type of tubular rod or beam that has one end fixed to the chassis or body of the vehicle (in case of a unibody construction) and the other is twisted by a lever which is connected to the suspension. Currently, only certain American trucks and truck based SUVs are still using torsion bars suspension systems.

Towing weight

This term describes the maximum weight of a trailer or boat that a vehicle can tow according to manufacturer imposed standards.


The track is a term which describes the distance between two wheels on the same axle.

Traction Control System

Developed to minimize wheel slippage through turns and low grip surfaces, Traction Control works by using the ABS wheel sensors to detect if any of the wheels is spinning uncontrollably and individually brake it or even reduce engine power until the grip is restored.

Transfer (gear)box

A transfer gearbox (or transfer case) is a system of gears used to transmit power coming through the transmission to the front and rear driveshafts. Used in four-wheel drive vehicles, transfer boxes usually employ only two gears - low range and high range - which are used mostly in off-road conditions.

Transmission (gearbox)

The transmission (also called gearbox) is a gear-changing assembly which consists of a number of gears and other associated parts and it is used to transfer the power from a vehicle's engine to one or more driving axles.

Turbo Diesel direct Injection

TDI is Volkswagen's AG trademarked moniker for their Turbo Diesel direct Injection engines. While in the beginning they were all direct injection engines, now common rail ones also bear the same name in the VAG group.


Designed to improve the volumetric efficiency of an internal combustion engine, the turbocharger is a forced induction device which can increase an engine's output. It is essentially a turbine driven by the exhaust gases which sucks in air and forces it into the cylinders, unlike the supercharger, which is mechanically driven by the engine's crankshaft.

Two Wheel Drive

This expression is used to describe a vehicle with only two wheel drive. The first figure is the total number of wheels, and the second is the number of driving wheels. In some countries it's essentially a different name for rear-wheel drive vehicles (RWD), unlike 2X4, which can be used for describing a front-wheel drive vehicle (FWD).

Two-wheel drive

Two-wheel drive (or 2WD) is referring to any vehicle in which the drivetrain is sending power from the engine to a single axle (to only two wheels). Two-wheel drive vehicles can be either FWD (front-wheel-drive) or RWD (rear-wheel drive), and each has its advantages and disadvantages.