That would be neat if that was how it worked! But I think Pixar choose not to do something like that because it isn’t really necessary. Telling the genders apart is typically pretty easy and I’m sure it would be no problem for the cars themselves to tell the difference between male and female, just like we do as humans. And of course there are still those moments when sometimes you just don’t know… 
I honestly think their voices, appearance, and make-up or lack thereof is enough distinction. 
What about metrosexual cars or flaming cars that just have really feminine voices? If a Car gets a paint job does that automatically become a sex change?
Then they would have feminine voices - you answered your own question. A guy doesn’t have to be metrosexual or flaming to have a feminine voice either. He could just be born with one.
If the character really is that important, you’d still hear them say his name at some point in the movie.
If a car gets a paint job, no it doesn’t change the birds and the bees. Come on now…if a guy put on a pink shirt with bunnies, that doesn’t make his bee change, does it? 
But if it’s just based on superficial appearances like eyelashes and voices, what’s to distinguish a real female car from just a transvestite car with a really high feminine voice?
And I still don’t see how Cars can have babies. They don’t have genitalia nor do they have the necessary, erm, pistons in order to biologically spawn. So how could they possibly reproduce sexually?- No wait on second thought don’t answer that.
Really the only way I can think Cars can have babies is if they do something like in Robots where they just buy a Car Baby kit and then put it together. Which would make the Male-Female concept completely moot.
I hope I don’t sound like I’m purposefully trying to argue against your theories, x3haijessiex3. It’s just, argh, lots o’ FridgeLogic with the series.
That’s my point. To them it isn’t based on just appearances. It’s based on whatever is genitalia to them.
To them.
We aren’t cars so we can’t possibly know. Who’s to say that in their world, cars are made the same as our world? Maybe because they populate their world, they have genitalia. We wouldn’t know though. When Lightning drives in on Sheriff, he obviously sees some type of car genitalia because he gets embarrassed and hides his face.
We don’t have to see or know how cars have babies, but we know they have them - so that’s all that matters. They do give birth though, because in some of the characters desctiptions they would say things like, “He was born to do this…when he was born…at the time of his birth…”’
EDIT: As I’ve said before, I have fun talking about this stuff! Don’t worry about it! 
I agree with Jess. I think it’s pretty obvious which cars are which gender.
I’ve never thought about that! Drag Queen Cars! Awesomeness.
Yeah, that problem still hasn’t been solved. But, we already came to the consensus that the more direct, physical parts of a car don’t conclude it’s own gender. Also, the ‘attachments’ of the cars maybe just how the car portrays itself, i’ve always heard that, depending on the car that someone is using, it really tells you a lot about them through that vehicle, either by the rims, or anything else.
You keep comparing their world to ours as if it will ever make sense.
In their world, they have their own ways. It’s as simple as that.
I could not agree more. It is a waste of time to try and find the faults and loop-holes in this. It’s a movie to start with, so there are obviously going to be some things that are un-realistic or cannot be explained. Second, exactly what jessie said, they live in a different world than us. There are no humans in the movie! Man, just imagine how bad urbanization must be there…considering everything (buildings etc) is probably like three times larger…LOL sorry I kinda went off topic there.
Did you see the size of the building compared to Holley in that trailer? Everything must be gigantic!
I know! A big city would literally be a big city!
I would love to just stand in their world - just to see what it feels like.
Would a Car’s school be considered Driving 101? 
No, I think the parents teach them how to drive like our parents teach us how to walk.
Yeah I think so too. But they must get some kind of an education right? I wonder what a cars classroom would look like!!!
I never said they didn’t have school. We know it exists though, because Lightning always bothers Chick about the fact that he never graduated.
also, how would their getting of a permit or a ‘driver’s license’ work out? They’ve been born to walk driving!
It doesn’t exist there. They just learn from their parents like we learn from ours.