Continuously Variable Pains?

In Bangladesh, car owners are a lazy bunch. They like everything to be automated, hence automatic transmissions sell big. But these days you hear a lot about CVT gearboxes. They are like automatics but only different. How? Well, they work by magic. Most people don't know how they do what they do. As a result, there are many myths and headaches resulting from poorly maintained, CVT equipped cars. Let's take a look into what they are, how they work and why they sometimes refuse to work no matter how much you beg your car.

THE DIFFERENCE Automatic transmissions are like regular manual transmissions. There are a finite number of gears (typically four speeds). As you speed up, the gears shift one after the other without you having to think about it. Each time the gear changes up or down, you feel a jolt. You smile knowing it is working. CVT on the other hand, stands for Continuous Variable Transmission. It has a wider, almost infinite range of gears (or speeds). They are constantly changing in relation to the car's engine speed. What this means is, if you step into a CVT equipped car for the first time, you will feel weird.

HOW DOES IT FEEL? Like I just said; weird. With a normal automatic, your car accelerates followed by a jolt as the gear moves up, then more acceleration followed by a proportionate rise in engine noise and so on. The jolt brings drama to our slow lives. With a CVT, there is no drama. The car accelerates seamlessly without jolting. Unfortunately, it sounds like it is revving without accelerating much, as if the clutch is slipping and is worn out. This is normal.

EH? Floor the accelerator in a typical automatic and you feel a surge. Ooh, 'turbo', right? In case of a CVT, flooring the accelerator raises the engine speed to the optimum level but the car starts off not as fast as you'd expect. You get a lot of 'vroom' but the accompanied 'go' is sedated. Then there is a steady, quick increase of speed without any shifts. Some people think this is slower but its actually faster than a similarly powered car with a typical automatic. Some cars offer an electrical simulated 'jerk' so people aren't scared by the apparent smoothness of magic happening.

THAT'S ALL GOOD, RIGHT? Well, yeah. CVT always keeps the car in its optimum power range, unlike a regular automatic. It's a little whinny but you get better acceleration, better fuel efficiency. Which is why a typical 1.5 Toyota Axio or a Honda Jazz will give you upwards of 10kmpl fuel efficiency.

SO WHAT'S BAD? It's new tech and many service centres, mechanics and owners are yet to catch up to it. Drivers used to a manual or automatic will think that a CVT is faulty because the engine speeds rise up and down eerily. As stated earlier, in a conventional transmission, this would mean the clutch is slipping. In CVTs however, this is normal. Unfortunately, many mechanics and drivers make the incorrect diagnosis and try to remedy it. Often, they will look into topping up gear oil, sometimes with the wrong kind of oil. And that's how they really kill it. CVT fluid is different than normal ATF (auto transmission fluid). It's like how water and acid are similarly liquid but are completely different. Simply put, CVT will die if you put normal ATF in it. CVT will also die if you put too much oil into it.

SOUNDS SIMPLE BUT HOW TO AVOID KILLING IT? CVTs do not require regular 'topping' up. Not all CVTs are the same, so they require different type of attention. But the common consensus from most manufacturers is that CVT fluid doesn't need replacement. These fluids are 'made for lifetime of transmission'. Most manufacturers have service intervals such as 30k, 60k, 120k kilometers. At each of these intervals the fluid composition is checked by technicians and refilled at around the 100000 km mark. DHS (Honda dealer in Bangladesh) say their cars are sealed for the lifetime of the transmission. But if you have to service it, replace the old fluid with the proper type, replace the filter and clean the oil pan. Problem is CVT fluid is usually 5-8 times more expensive than ATF, so many people unknowingly just pour in some cheaper ATF. Another major killer of CVT is the cooling system. Make sure your radiator and coolant is perfect because that system is also part of the transmission cooling. Overheating will cause your CVT oil to deteriorate. This is Bangladesh and it's always on fire.

SO BASICALLY… Don't top up the CVT fluid cause you can risk overfilling, which can cause problems followed by a telltale whining sound. There's a way to check the level. Do it when the car is cool so the level is at the right mark. If you ever have to replace oil, do it only with the proper CVT fluid which is much, much more expensive. Replace filter and clean the oil pan as well. Get it done by a technician who knows what he's doing. Maintain your cooling system with proper coolant servicing.

If you have questions on how not to destroy your car, mail us at shift@thedailystar.net