In diesel engines, the timing system is normally composed by gears, sometimes with toothed belt and recently with chains. But for trucks and buses, vans and SUV's the most common is gears due to reliability. But this reliability can not be misunderstood with durability, other wise some gear noise can appears and this noise can be considered as a kind of failure at least in terms of comfort.
The gear train can produce mainly two kinds of noise, rattle and whine, in this paper we will discuss about the whine noise.
The discussion will be done based in a case with the 4.07TCE Sprint engine.
Definition - It is a tonal gear frequency and their harmonics. 
In this paper we will analyze how the whine noise is presented, what are the significant factors and how to deal with them.