A gear is supposed to stay in its designated position until a shift is performed, by the driver in the case of a manual transmission vehicle, or by the on-board computer – an electronic facility – in the case of the automatics.
If the transmission is spontaneously slipping in and out of gear, or is simply too hard to shift, even into neutral when one intends to start, then I don’t need to tell you that this could constitute a serious safety risk. You need different power ratios delivered to the wheels from the gearbox, and the only mechanism through which one can do that is the gear lever, which is designed to shift gears smoothly.
But whenever there is difficulty in doing so, or even when the gear tends to slip out of position, then there is definitely a problem.
Let us examine what would bring about one of the above conditions:
In case the link that holds the gears from moving is worn out or broken. When this happens, there will be a slippery gear movement because the link which is supposed to move the different gears, such as from ‘P’, or parking, to other gears, is totally broken.
When a wrong transmission fluid type is used. As soon as one uses the wrong transmission fluid that is not meant for that particular gearbox and engine, it will automatically harden the gear shift movement, and if it is forced, it stands the risk of getting damaged and eventually breaking.
Too low or too high levels of transmission fluid will also harden the shifting of the gear lever.
At times there are some internal transmission failures. For example, whenever the tubes that convey the gearbox fluid are somewhat blocked by dirt, then there will be some difficulties in the gear shifts.
Whenever there is a failure in the electrical or computer operations of the transmission, then it will obviously lead to hardening of the gear shift from any position of the gearbox.
Finally, when the engine experiences a complete and total failure, then it will affect the performance of the gearbox, most especially when one tries to shift the gears to the different positions.
All in all, hardening of the gear shift is something that one shouldn’t take lightly. It is usually a sign that something is very wrong and needs urgent attention by a competent mechanic. And now that you know most of the telltale signs, you will ignore them at your peril.
Source : The Observer