I am not sure if I understood correctly or not, but I guess you might want to get properties with values for "Trucks" in your ThingWorx platform, not just from one truck, right?
If yes, you might have defined a thing template for trucks. Then you can get all implementing things with data from the thing template by using below rest api.
One thing you have to remember is that the "post" method is not enabled by default because of security issues. So if you want to execute services thru rest apis, please make "Allow Request Method Switch" enabled from the "PlatformSubsystem" in your composer.
You can use the REST API to get properties off of a thing like this: http://localhost/Thingworx/Things/MyThing/Properties
To retrieve this as JSON, add "?Accept=application/json" to the end of the previous link
Hope this helps!