In the Chevrolet CK1500, you push accelerate and it has a sound, but if you can go a bit fast, there is ANOTHER engine sound, and they both sound at the same time and it sounds like there are literally 2 engines running.

This has been going since the has been released. Think about it, a normal player clicks new game, pushes accelerator and in 15 seconds hears this. It can definitely give the wrong idea about the polishing of the game and its literally in your bests interest to make the firsts minutes of the game very polished.
I think no other truck has this problem, just this one.