update: changed all stereo wav files to mono, as stereo is a little glitchy. mainly, the sound doesn't fade till the car is 500 meters away.
and to devel, here's a tip: export wav files to MONO from now on, not STEREO.
I Know, but give me a tutorial because when I do it, it seems to make a duplicate, then there is nothing. I edited the .truck file and followed the instructions, but it doesn't work. Can you please give me a picture tutorial?