Backstory for how They Could Meet:

They meet on Earth. Moonracer was helping bring some supplies to the earth base that Alpha Trion wanted to send them. She was going to stay there for a few days before heading back. The earth crew then sent her out on a patrol, where she found Nightbird. (Basically, while Moonracer was on patrol, an explosion happened in the distance, which sent a shockwave out, knocking her to the ground and knocking Nightbird out a tree. They then both freeze. Moonracer comms the other Autobots asking if she is needed in dealing with the explosion. They say it's just Decepticons, and she is not needed. She then turns to Nightbird and goes "Well, that is not my problem. Is it yours?" Nightbird nods no. (Moonracer is still itching to help though.))

Then, they start meeting up, as Moonracer knows earth sign language, and gives Nightbird a datapad on cybertronian sign language. (Nightbird doesn't speak. She is mute.) Then, when Moonracer goes back to Cybertron, Nightbird sneaks her way onto the ship and goes with them. Moonracer doesn't realize until they get to Cybertron, and decides to keep Nightbird a secret as Nightbird asks her too. (Moonracer did do a bit of research and found that Nightbird wasn't an enemy, she is technically a neutral.) Once on Cybertron, they start getting closer. They go through ups and downs and stuff.

Some Things That Happen Aomewhere in the Timeline:

Powerglide tells Moonracer about his relationship with a human, which Moonracer internally connects to her feelings about nightbird ( as Nightbird isn't a Cybertronian). She feels more secure in her emotions after this.

Nightbird saves Moonracer after Moonracer lets her confidence overtake her actions.

During a mission, they get attacked and Nightbird vanishes, abandoning Moonracer. This leaves Moonracer pissed. (Nightbird doesn't trust people, and looks after herself.) The next mission, Moonracer still goes back for Nightbird after shit goes wrong. This causes Nightbird some thought. The NEXT mission, shit goes wrong once again. Nightbird disappears again, but then decides to go back and help Moonracer.

There becomes a time where they both realize they are both inexperienced in life.

Why I Think These Two Would Work:

So, both of them are very skilled mechs, and both value skills. They are both younger, so would be in the same maturity. Nightbird has trust issues, and could learn to rely on Moonracers skills. Moonracer is also very kind and loyal, so she would not just give up and abandon Nightbird. But Moonracer would also stand up to Nightbird, which Nightbird would respect and listen to. Both are intelligent and resourceful, which would cause them to respect each other. Moonracer takes mistakes to heart, and Nightbird could teach her to learn and move on from them. Nightbird's level of dark sarcasm would contrast nicely with Moonracer's bubblyness.