The phrase "base chassis" refers to the foundation or main structure of a vehicle. It is the framework onto which all other components, such as the engine, wheels, and body, are built or added. Full definition
The new road cars use the same base chassis, engine and philosophy of the team behind the development. (swedespeed.com)
The vehicle looks like nothing more than an up - sprung V40, and is an engineering mule, which is most likely using a CMA platform based chassis. (team-bhp.com)
However, all Ram pickups and pickup - based chassis cabs include Electronic Range Select (ERS) with all automatic transmissions. (ramtrucks.com)