Some drivers prefer the “labour-saving” benefit of allowing the automatic gearbox to make all gear changes for them, allowing them to keep both hands on the steering wheel more of the time.
Since there are many manifestations of the auto’ ‘box, it is not possible to give authoritative guidance in regard to best practise which would be applicable in all vehicles. What is clear, however, is the need to seek the manufacturer’s guidance in the vehicle’s handbook, and to assess any potential benefits of overriding the auto’ ‘box during your planning on the approach to individual hazards.
An auto’ ‘box will respond to road speed, engine speed and load, but cannot see what the driver sees. Thus it can only react – never anticipate.
Therefore, it can be argued that there will be times when it is advisable to manually override the automatics. Knowing this manufacturers invariably design a “selector” which, in addition to Park, Reverse, Neutral and Drive, has positions allowing the driver to “lock-down” into lower gears (often marked 1, 2, and 3, or Low). Some more modern vehicles also have a function of the lever and gearbox that allows the driver to shift sequentially through all of the gears, by simply pushing forward or backwards on the lever to change up or down.
Others have F1-style “paddles” or buttons behind or on the steering wheel which do the same thing.
It is important to note that manually selecting say, “2”, on the selector lever, does not automatically mean that second gear will be engaged. The vehicle’s road speed will need to be in the “speed range” of 2nd before the auto’ ‘box will engage 2nd gear. Also, should position “2” (or 3) be selected whilst stationary or moving very slowly, most auto’ ‘boxes will pull away or crawl in 1st gear and ultimately be limited to an uppermost of 2nd (or 3rd) gear, the ’box automatically changing up and down between the lower gears depending upon road and engine speeds, and load. Most units now have a total of 5 gears.
Significantly, it is wrong to use an auto’ ‘box as though it were a manual. It is not necessary to change down manually simply because you would change down if you were driving a vehicle with a manual gearbox.
Hopefully the following ‘pointers’ will assist your assessment of whether it might be useful to override an auto’ at times.
When negotiating a series of bends, control and stability might be enhanced by locking-down. In doing so the gearbox will be prevented from changing up beyond the gear selected, retaining more engine braking to assist you to use acceleration sense to string a series of bends together, perhaps without resorting to the brakes unnecessarily;
In slow moving traffic queues greater responsiveness to the throttle can be had by overriding an auto’ ‘box, assisting you to maintain position with less braking in some vehicles;
During a long, steep ascent overriding an auto’ ‘box may prevent the ‘box from repeatedly changing up and down searching for the best gear.
Pressing the accelerator fully will normally cause an auto’ to change into a lower gear (“kick-down”), giving rapid acceleration. When pressure on the accelerator is released sufficiently, however, the ‘box will automatically change up. If wishing to re-enter a line of vehicles after an overtake, the resultant run-on (due to a lack of engine braking) might not be useful, and thus overriding the ‘box by locking-down might be prudent planning before overtaking. Also, the “jerk” which is often encountered by “kickdown” can be avoided;
Finally, it is said that selecting neutral during temporary stops causes more wear on the transmission than leaving the selector in gear.
