In front wheel drive cars, what component combines the differential and transmission into a single part?

The transaxle is the correct answer because it is a crucial component in front-wheel-drive vehicles that integrates the functions of both the transmission and the differential into one single unit. This design streamlines the drivetrain layout and contributes to a more compact configuration, which is particularly advantageous in front-wheel-drive systems where space is at a premium.

A transaxle allows for the combination of gears necessary for transmission, alongside the differential gears that enable power to be distributed to the drive wheels, which is essential in maintaining traction and proper handling. In essence, it plays a vital role in the mechanics of front-wheel drive cars, contributing to their overall efficiency and design.

The other options do not serve this combined purpose. The bell housing primarily encloses the flywheel and connects the transmission to the engine, while constant velocity joints are used to allow for flexible movement and power transfer while the vehicle is in motion. A torque converter, on the other hand, is a type of fluid coupling used to transfer power from the engine to the transmission but does not integrate the transmission and differential. Thus, the transaxle distinctly serves the purpose of merging these essential components into one cohesive assembly in front-wheel-drive vehicles.