How to care for auto transmissions

Mercedes-Benz 9-Gang Automatik 9G-TRONIC, 2013 Mercedes-Benz nine-speed automatic transmission

Mercedes-Benz 9-Gang Automatik 9G-TRONIC, 2013 Mercedes-Benz nine-speed automatic transmission

Published Aug 29, 2013

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Having recently encountered a real problem with an automatic gearbox, I asked a few of my colleagues in the business about the new automatic transmissions on the market - and discovered I was not the only mechanic to encounter problems with these gearboxes.

When you have a problem with a modern auto the vehicle has a very clever system that instantly puts the car into a safety or ‘limp home’ mode. What this does is to allow you to drive home, rather slowly, but with minimum damage to the gearbox. There should also be a gearbox fault light that will come on in the instrument cluster.

When this happens get the vehicle to the nearest dealership or service centre that can deal with this problem. The petrolheads among us are already aware of the fact that the new auto boxes are mostly electronic, which means the problem can be identified by plugging in a diagnostic machine.

There are cases where only a replacement solenoid is required - but in many instances the results are not favourable and a new gearbox is needed.

Oil levels in an automatic transmission are very important.

When the oil level is low, the gearbox clutches are in danger of slipping, thus leading to clutch failure and ultimately gearbox failure.

With all the new technology on the market you would imagine that gearbox failure would be a rarity. This is not the case - but some manufacturers still recommend that the oil in an automatic gearbox should never be changed. I find this a bit confusing because if you changed the oil and gearbox filter at 60 000km intervals, you would extend the life of said gearbox.

When I asked manufacturers’ representatives why the oils in the new automatic boxes are never changed, it was claimed that if the oil and filter were changed it would affect the friction ability of the clutches as the wear on the clutches could not be compensated for with the clean oil.

The jury is still out on that response.

The cost of repair on a modern automatic gearbox can be exorbitant, from R25 000 upward. If the vehicle is under warranty the cost is borne by the manufacturer, provided that all services and repairs have been previously carried out by said manufacturer or dealership,according to manufacturer’s specifications and service intervals.

But if the car is out of its maintenance or service plan, and is not maintained by one of the manufacturer’s dealerships, a huge dent could be put in your monthly budget and holiday savings.

So how do you ensure that this does not happen to you?

1. Insist that the gearbox oil level is checked at every service. You will be charged for it if it is not on the service schedule, but it will be worth the cost.

2. Ask that the oil and filter be replaced every 60 000km. On some auto boxes this can cost as much as R4000 but again I believe the cost is worth it.

Despite the fact that automatic cars cost a lot more than manual vehicles, they do make driving in peak traffic considerably easier.

So more manufacturers are designing ever more complicated gearboxes, with up to nine speeds, and I shudder to think of the financial implications when these gearboxes fail. - Star Motoring

Sagie Moodley owns a workshop in Midrand and also presents a radio motoring show with Adam Ford on Mix FM (93.8) from 7-9pm every Wednesday.

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