Recently, Ivan Musana had to replace the gearbox of his Toyota Corolla. One day as he was stuck in traffic jam, the gears could not engage. He recalls a cloud of smoke emanating from the car bonnet.
The car was towed to a garage where after checking the mechanic said the gearbox was low on oil and the clutch was burnt. The solution was to have the clutch and the gearbox replaced, which cost him about Shs2m.
Peter Amadi, a mechanic at Dalas Auto Limited in Bunga, says gearbox mechanical problems are similar whether your car is manual or automatic.
Like in Musana’s case, the commonest cause of gearbox failure is failure to service it on time. In the end, you lose the gearbox while the clutch is also damaged.
“If the gearbox oil and the strainer are dirty and are not replaced regularly, it means the oil filter will be chocked. You cannot get the gears you want. The moment the clutch plates are starved of oil, they will get burnt. At the end of the day, you either repair or replace the entire gearbox,” Amadi cautions.
A number of drivers will not notice any oil leakage until the car fails to start. Alex Kadoli, a mechanic in Bunga, observes that as a motorist, you contribute to gearbox damage by not checking oil levels even after you have noticed a leakage. “When you use the wrong automatic transmission fluid (ATF) or hydraulic oil, it damages the gearbox. When you check the dipstick, it warns you about the right ATF to use. When you use ordinary hydraulic oil, the car cannot move until you use the recommended type,” Kadoli says.
Amadi says an automatic gearbox requires replacing gearbox oil, strainer and cleaning before putting new oil. You also have to replace oil filters, cleaning the sump, valve body and the filter inside the gearbox.
When you drain old oil without replacing the oil filter, the old one will not allow easy flow of new oil within the gearbox.
Amadi says balancing the manual gearbox when driving is a common problem as most motorists do not understand how manual cars are driven. When you try to balance the car in traffic jam or on a hill, you end up burning the release bearing and this breaks the gearbox.
“When the gearbox is broken, the car abruptly stops and you cannot engage any gear. In this case, the bearing melts on the gearbox shaft and it breaks the whole gearbox. The solution is to replace the gearbox and the shaft,” Amadi advises, adding that reliability of automatic and manual gearboxes is the same as long as you carry out schedules servicing.
Service of gearboxes
Regardless of whether your gearbox is manual or automatic, it is recommended for major service twice a year, unless there is a leakage. Alternatively, you can also service the gearbox by following the service manual. Do not go for cheaper hydraulic oil to save money. “You do not need to be a mechanic to understand that your car needs service. Teach yourself to look out for some key parts such as oil levels,” Amadi advises.
In automatic cars, a failing gearbox will delay to engage gears. There is also excessive shock engagement where the car engages gears as if the whole car is braking.
If your car is an all-wheel drive (AWD), turning the car will feel as though you are turning a lorry and behaves normally on a straight stretch.
In manual gearboxes, the centre double differential, commonly known as the double diff, where the drive comes from, when you try to engage gears, the gearbox makes a sound as if it is braking because plains in the gearbox are not linking up well. With less oil, the heat builds up and you start losing gear engaging forces.
Driving habits that spoil gearboxes
While driving at a fast pace over a short distance and you engage the brakes, it damages the gearbox. This is because the car ought to pick up speed and gears gradually. The cost of replacing a gearbox depends on whether it is new or old and whether it is for an automatic or manual car. On average, you will have to spend between Shs900,000 to Shs7m.
Peter Amadi, a mechanic at Dalas Auto Limited in Bunga, says in manual cars, motorists do not know how to downshift. Downshifting is driving from a higher gear to a lower one to allow you control the car. For example, if you are driving at 160km/hour, you are supposed to be in gear five. When something appears ahead of you where you cannot brake abruptly, you have to engage, say gear three to stop the car.
“If you are driving at 140km/hour and you want to control the car at gear two and you release the clutch fully, the engine might blow. You are not supposed to release the clutch fully to avoid straining the engine,” Amadi advises.
Poor gear selection
Alex Kadoli, a mechanic in Bunga, says in a manual car, you cannot engage gear five while driving below 100 kilometres. The car starts to vibrate because it is asking for the right gear and when you keep on pushing and it picks up, you spoil the gearbox. The higher the speed, the higher the gear and the lower the speed, the lower the gear.
According to Amadi, the most commonly skipped gears are three and four, especially at a time when the car is picking up speed, and the driver goes to gear five. This happens when most drivers are tired. You forget that gears have synchronising points in the gearbox and rings that help you select a gear. If they are not used well, they get stack.