All transmissions have neutral speed. However, it has different functions for different types of transmissions. For example, in a manual transmission, “neutral” is used to disengage the output and input shafts. In automatic transmissions, on the other hand, with few exceptions, “neutral” puts many mechanisms, including the oil pump, into rest. However, everything is not simple with manual transmissions these days.
The use of “neutral” in manual transmissions of the past
In cars of the 1850s and 1970s, high engine speeds radically increased engine temperature. In those days, water cooling did not do a good job, which led to the boiling out of coolant. For this reason, many drivers (especially truck drivers) had to drive “jerky”: accelerating in gear – coasting in neutral. The coasting motion allowed the engine to cool. This, at first sight, simple driving technique was taught in all driving schools. Almost every driving instructor agitated for it. In addition, neutral was actively used by drivers for short stops with the engine running.
The use of “neutral” in manual gearboxes of today
Nowadays cars are seriously different from those made in the last century. Even from those made back in the 1980s. And therefore the old techniques of driving with the use of neutral in the vast majority of cases for the car are frankly harmful. All because the development of systems of cooling has seriously stepped forward. In particular, the system of constant pressure lubrication, functioning separately from the oil pump was invented. It means exactly that power units ceased to be afraid of continuous traction. Often, high rpm is even useful for the engine, as the higher it is, the better the pump, pump and vacuum booster work. Nowadays, it is recommended to use neutral on cars with “mechanical” only in case of a stop.
Using “override” in automatic transmissions
In the case of automatic transmissions, everything is somewhat more complicated. However, here it is not necessary to activate neutral even at stops. In the classic “automatic” neutral gear is needed only for towing the vehicle for short distances. This is because the transmission of torque of such automatic transmissions is carried out through a hydraulic clutch, which allows the rotation of the shafts without physical engagement. Moreover, the use of neutral while driving is harmful, since the activation of N puts many mechanisms and the oil pump at rest. In other words, the constant shifting between N and D forces the automatic transmission to do an inappropriate job and, in turn, noticeably accelerates the wear of the transmission.
Exceptions are robotized automatic boxes, based on manual boxes, as well as preselective “robots”. In their case, N mode can and even should be used at stops, as it allows protecting clutch disks from overheating.