Not sure if you are asking about all parts or not.
Anyways, the 2.4L 4-cyl engines (LE5 / LE9) are the same in the Cobalt and Malibu. Also, they run the same hubs (wheels are swappable between Malibu and the Cobalt). However, that is where the similarities end. The Malibu runs strictly a 6-spd auto (majority, I think there are some 4 speed autos as well), while the balt runs 5 spd manual and 4 speed autos. The suspension is also different between the two.
What were you looking at upgrading? Go fast bits or handling (or both)!?!?!
Anyways, the 2.4L 4-cyl engines (LE5 / LE9) are the same in the Cobalt and Malibu. Also, they run the same hubs (wheels are swappable between Malibu and the Cobalt). However, that is where the similarities end. The Malibu runs strictly a 6-spd auto (majority, I think there are some 4 speed autos as well), while the balt runs 5 spd manual and 4 speed autos. The suspension is also different between the two.
What were you looking at upgrading? Go fast bits or handling (or both)!?!?!