As the mom of two boys, I've had to make 'truck noises' since they first started flipping through picture books and playing with 4-wheeled vehicles. And I have to admit - I'm terrible at making truck noises! Their dad can do it, their uncles can, Grandpa and Pepere are experts but me (and Nana and Grandma) don't stand a chance. I've really tried over the years - motorcycle sounds, trucks crashing, helicopter propellers - but no matter which vehicle I try, it sounds terrible!
So the boys found a solution - they give me the beat-up van to play with! It's the one that looks most similar to our mini-van and doesn't have any cool sounds associated with it! So while they get to drive all the cool monster trucks and race cars and instinctively make the appropriate sound effects, I travel silently. And even when I try once again to master the 'vroom', I get side-ways glances from them that let me know I should leave well enough alone.
So my answer to whether truck noises are nature or nurture, I'm going with nature! Perhaps some day I'll start a support group for all of us 'moms of boys' who desperately want to enter their world of trucks but for now I'll sit back with my 'van' and try not to look disappointed :(