The 1989 Micromaster Transports aren't especially well-remembered today. Like other, larger, Micromaster sets such as Airwave, the Transports came with a small figure that turned from a robot into an alternate mode, as well as a transforming accessory. The Transports were sold at a lower price-point than Airwave and those like him. Airwave came in a small box, while the Transports came on cards.
I don't know if anyone else ever thought this way (I wrote this while the TFWiki was down. It seems that I'm not), but I always saw Overload as a kind of "Micromaster Optimus Prime." This is admittedly for no reason greater than the cab and trailer alternate mode and very loosely Prime-like colors (Overload is blue where Prime would be red, and vice-versa)....
...well, the fact that Overload has a similar "truck windows on chest" torso (kind of an Optimus Prime trademark) also helps. But even if the colors were reversed to Prime-proper, the proportions and lack of face plate would be a dead giveaway. At least, it would have been in 1989, before Primes were released having mouths! (Of course, those linked Primes were just recolors of molds that were created to represent non-Prime characters, so maybe that doesn't really mean anything...)
Overload's trailer transforms into a kind of fighter jet. "Kind of" a jet, that is, if you ignore the laws of aerodynamics, and "kind of" a fighter if one imagines that the ends of the wings are supposed to be weapon-tips. This is one of those instances where you can tell that the package art took some liberties and added details that the toy does not possess (of course, the art may reflect design elements that the toy was intended to possess at one point in time, but I don't know this for certain).
One element of the design of Overload's trailer that I don't think gets enough attention is that the back of the trailer opens up to allow for other Micromaster vehicles to ride inside. This part doesn't need to move for transformation. It pretty much only serves the play factor of the toy's trailer mode. I always appreciate it when toys have these extra elements, especially in the original Generation One era.