Car Care: How to spot automatic transmisson issues
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Whether it’s a vehicle you own or one that you’re about to buy, it’s most probably fitted with a transmission of some description. But how do you know that the transmission is any good?
With the Christmas period a popular time for towing, signs of problems and preventative maintenance might even prevent a breakdown.
As this is one of the most costly components of a motor vehicle to repair or replace, it certainly pays to know.
When to expect transmission troubles
Many transmission issues can be due to lack of servicing or not using the correct fluid type. Transmission fluid degrades over time and can be affected by heat. A general rule of thumb is to change the fluid roughly every 30-50,000km, or more frequently if the vehicle is used for towing or carrying heavy goods.
Nowadays, transmissions are high-tech and require a particular fluid whether it’s a CVT, DSG or conventional transmission type.
Some transmissions are classed as “Fill for Life” or “Sealed” (without dipstick) and don’t have a manufacturer’s recommended replacement interval under normal driving situations. The term “Life” could mean the manufacturer’s warranty period or 100,000km, and it might be that the fluid requires a change at least once in the vehicle’s life.
Very similar to a slipping clutch in a manual, an automatic can slip or “flare” between gear changes. In the early stages of trouble or in vehicles without a tacho it may be difficult to detect, but if the engine seems to rev more than normal and no longer matches the vehicle’s momentum, then you could have a problem.
This is not to be confused with CVT transmission operation, where the revs may hold steady while speed increases. This can often be translated as a “slipping” sensation, but doesn’t necessarily indicate a problem. A common complaint for CVT vehicles is shuddering on take-off — this symptom can be fixed by a fluid change and the addition of an anti-shudder additive but it can also end up quite expensive if more work is required.
This one’s a bit easier to detect, as there’s a noticeable “clonk” when engaging drive from park, reverse or neutral. Gear changes can also feel harsher than usual, disturbing an otherwise smooth drive down the highway. This could also be a symptom of a worn driveline component that needs further investigation.
This could be evident when you go to reverse out of a car park then suddenly hear a loud “bang” upon acceleration. This could just be an indication of low or dirty fluid, or in the worst case, an internal component malfunction is causing gear selection delays. This is a common symptom experienced in used vehicles. To help prevent further damage until the vehicle can be repaired, it is best to delay accelerating for a few seconds after selecting a gear.
Total fluid loss will stop any transmission dead in its tracks, and it’s commonly attributed to a split or perished cooler hose. A leak over time can do the same thing, but can potentially cause more damage as the transmission has to work harder to try and maintain drive. Slow leaks can be from a simple gasket or seal and over time fluid can spread and look like a combination of leaks — a clean-down should pinpoint the location.
If your transmission is making buzzing noises it could indicate low fluid, or that the fluid is not able to be pumped around the transmission due to a blocked pick-up or dented transmission pan.
If you notice burning smells, it could be from an overheated transmission or due to a component slipping and failing inside. Transmission fluid is usually bright red in colour but it turns black if overheated. Overheating is one of the biggest causes of premature transmission failure (over 80 per cent) so it makes sense to add extra cooling. For this reason, an external transmission fluid cooler may need to be fitted on vehicles that tow significant loads. Overheating can happen if you’re in slow-moving traffic on a hot day, or slowly pulling that heavy trailer up a long hill.