the twins, and jolt

i recently read the comic movie adaptation, and i have two things i would like to address about the movie, and get some opinions on.
in the beginning, the twins combine in ice cream truck mode, and i guess reformat later into the chevy beat in trax. do they retain the ability to combine? there has been talk of this, but the book showed no evidence of it.
secondly, i didnt see jolt ONCE. nor have i seen him in the previews. so why would chevy dedicate a new vehicle to an alt mode of one of the tformers, if he doesnt even show up in the story?
in the beginning, the twins combine in ice cream truck mode, and i guess reformat later into the chevy beat in trax. do they retain the ability to combine? there has been talk of this, but the book showed no evidence of it.
secondly, i didnt see jolt ONCE. nor have i seen him in the previews. so why would chevy dedicate a new vehicle to an alt mode of one of the tformers, if he doesnt even show up in the story?