Breakdown’s alt mode is some sort of armoured military vehicle (my money’s on the MaxxPro MRAP, pictured above). It’s not clear whether he adopted it in anticipation of combat on Earth or because it most closely resembled his Cybertonian (Velocitronian?) alt mode. Perhaps a little of both.
Regardless, one detail on BD’s vehicle mode always puzzled me. Them headlights:
Why does he have so many? Surely the standard set of two would suffice? They’re an uncanny alien touch on an otherwise passable Earth disguise, and I can only surmise that they’re there because BD had ‘em on his original, Cybertonian form and they were too difficult to remove or conceal.
But more than that, they might hint at Breakdown’s prewar occupation. Where might one need a lot of light – a lot of lamps – and maybe a nice big quarry hammer, too? My bet is Breakdown gets put on Decepticon mine duty not just because he plays well with Vehicons, but because that was what he was “built” to do: cracking rocks and harvesting energon underground, in the dark. Difficult and thankless work (to use Breakdown’s own phrasing), so you can imagine why he might have joined a movement that would have enabled him to move beyond his caste and into a more rewarding job (breaking faces instead of rocks).
The irony, of course, is that once he boards the Nemesis, he’s sent right back down to the place where he started.