May be a n00b question but what exactly makes the whining noise when manual cars are reversing? And how come some M/T cars do it and others do not?

 

Most manual cars do this because the reverse gear in the transmission is straight cut, rather than helical. Straight gears whine because there is a gap in between the gear tooth it is on now and the next tooth. the noise is the teeth coming into contact with each other. With helical gears, the teeth are always in contact with each other so there is no noise. That's all I know but I'm sure someone else can chime in and clarify why some cars don't do it.