The Troublesome Trucks (called Cars, originally known as Foolish Freight Cars, in the US narration) are always nicknamed so because they can be very troublesome, and love to play tricks on the engines, barring Edward, Stepney, Hiro, and Salty. The trucks have been the cause of most of the railway's accidents. However, since Douglas smashed the Spiteful Brake Van and Oliver pulled S.C. Ruffey, their leader, apart, they have been frightened of some engines.
There have, however, been some cases where the trucks and engines are on the same side, such as when Diesel was given a third chance on Sodor, but the trucks tricked him into misbehaving and getting sent away again. They also asked Percy to help move them from an ill-mannered and obnoxious barge named Bulstrode, only to end up in his hull and damage him, resulting in him being sent to a beach.
When Thomas and Edward switched jobs back when the former was a station pilot, the trucks pushed him down Gordon's Hill all the way to a siding. They then decided to trick James and him into a field. When James was given a second chance after ruining a coach's brake pipe, they tried to discourage him. The tail of the train uncoupled and the rest of the trucks rolled down the hill for James to recover. They later shoved him into some tar wagons.
Trucks were also a nuisance in the second season, as they refused to let Diesel move them out of a siding. This lead to an accident and as Diesel was forced to clear the mess, they taunted him with a song. Diesel blamed Duck for it and to get Duck back, made the trucks insult the three tender engines using the Great Western Engine's name. Devastated, Duck went to help Edward with his trucks up a hill, only for them to break away and cause Duck to crash into a barber shop, push Percy into the sea, tiring James, and shove Percy into a brake van.
They also bumped Thomas into a condemned track after losing their chance to pay James out and pushed Oliver into a turntable well. When the latter came back from the works, the trucks still laughed at him, but after he pulled S.C. Ruffey into pieces, they became loyal to him to minimise their chances of being ripped apart themselves.
The trucks also pulled Thomas down a hill into Salty and got James covered in melons.
The trucks teased James when he smashed them into the snow. When the Pack was building a new bandstand, they refused to move until Percy used his "do-as-I-say" whistle. They have since been good, but they soon decided to put a stop to their good streak by pulling Thomas and Percy down a hill and causing Stephen to get trapped in Ulfstead Mine. They have since been troublesome after this incident.
Thomas had once accidentally shunted them too hard and were just as confused as everyone else when Thomas blamed an imaginary engine named Geoffrey. They also laughed at Den when he was working at the quarry when Mavis was being repaired.
From Season 22 and onward the trucks are able to move onto their sides.
Every wise engine knows trucks cannot be trusted. Trucks could be considered the rebels and the troublemakers of all rolling stock on the railway, as most of them love to cause mischief and trouble and show no remorse for whatever they do unless told off by their engine. If an engine is having a bad day, makes a mistake, or is easily played upon, the trucks begin their wild antics of singing, name calling, holding back, shoving, bumping, giggling and so on. They will play tricks on an engine based on how they treat them. Most accidents caused by the trucks are a form of revenge due to mistreatment and they are not known for considering the consequences of their actions; they will carry out their plans even if they result in derailing, damaging or destroying themselves.
Trucks can also be described as territorial; when they get used to certain engines pulling them, another engine in the yard to take them may cause confusion or anger for the trucks. In Percy's Predicament for example, Toby and Percy switched jobs, making Toby's trucks furious and causing Percy to crash. In Oliver Owns Up, the trucks refused for Oliver to take them and demanded Duck, Donald or Douglas instead.
To the trucks, one engine is as good as another, as on one occasion they took their anger out on Thomas when they could not get back at James for bumping them.
During the thirteenth and sixteenth seasons, they behaved unusually well but were easily annoyed. From King of the Railway onwards, they have regained their old personalities, misbehaving and causing accidents.
Troublesome Trucks are based on 5 and 7-plank open wagons. In Journey Beyond Sodor, two Troublesome Trucks were based on 2-bar wooden slate wagons.
All the Troublesome Trucks are painted grey. Previously in the Railway Series and Model Series, they were seen in many liveries such as blue, red, green, yellow, orange, pink, brown and black. Privately-owned Troublesome Trucks typically have their own specific livery