Ask the Mechanic

Thursday March 11 2021
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By Paul Kaganzi

Where can I service a CVT transmission?

I recently bought a Toyota Fielder but did not know that it uses Continuous Velocity Transmission (CVT). After driving, it felt seamless and I was concerned. I checked the trans/axel number K310 which is mostly used in second generation Fielders and found out that it is actually a CVT type. My concern is whether we have the local expertise and spare parts for this type of transmission.

Richard

Hello Richard, your concern about the maintainability or repair of CVT transmissions is valid because there is a recent surge of cars with CVT transmissions on the used car market, yet the user awareness about how to use a CVT, maintenance and repair seems to be limited.

The biggest challenges with CVT transmissions lies in apathy among users and some maintenance technicians about their difference with the conventional automatic transmission, especially in shifting style and maintenance needs. The second challenge is maintenance and repair in the event of failure.

CVT transmission uses motor driven bands to shift gears instead of gear packs such as those found in conventional automatic transmissions. Herein lies the difference in operation and maintenance needs. The CVT transmission shifts continuously or seamlessly in tandem with changing engine ratios to achieve better fuel economy and efficiency while the automatic one shifts in noticeable steps.

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Motorists who are unaware that they are driving a car with a CVT transmission will assume that their automatic gearbox is slipping or faulty because of its seamless and varying shifting patterns. Whereas the CVT transmission bands require transmission fluid that provides a degree of friction to engage, the conventional automatic transmission requires fluid that provides lubrication and hydraulic pressure to engage the gear clutch packs. That creates the first maintenance challenge; where CVT transmissions cannot share fluids with the conventional automatic ones.

Another challenge is that different car manufacturers recommend different CVT fluid grades for their CVT transmissions. These CVT fluids are graded with codes and letters according to specific performance features and viscosity. The good news is, this information is available online and the fluids can be found with authorised car dealers both here and abroad.

The other maintenance challenge is repair of CVT transmissions when they fail. Usually, CVT transmissions fail due to fluid leaks, delay to service the fluids, use of wrong fluids, overheating or failure of electrical sensors or circuits. The technical knowhow to service and repair the CVT transmissions is growing. Authorised dealers and a growing number of independent garages and service centres have the skill set.

New repair parts can be ordered locally and from abroad. Used CVT transmissions are also available with a few dealers. The motorists must use common sense and available information to determine whether their car has a CVT transmission and, which provider is capable of servicing or repairing their CVT transmission when the need arises.

My car makes a cracking noise

Hello Paul, I drive Toyota Harrier 1998 model. However, it makes a cracking noise when going uphill and sometimes when I am driving on a level surface. It also sometimes takes a while to engage gear 4. What could be the problem?

Collin

Hello Collin, a cracking or crackling sound as you drive on level or hilly terrain can be disconcerting as well as dangerous. These kind of noises are usually from the steering linkages, wheel hub or final drive systems. The common causes or trouble spots are continuous velocity (CV) joints, worn out or bad shock absorbers and wheel hub bearing or knuckle ball joints.

CV joints work like the ‘wrists’ of your steering system and they connect the final drive from the transmission to the wheels. When their protective rubber boots tear, they tend to leak grease and let in dust, stones and water. Timely replacement of the rubber boot is crucial before the CV joints wear out and suffer seizure.

When CV joints fail, you cannot drive the car as it has no final drive from the gearbox. Worn out shock absorbers will also make that sort of noise when they leak hydraulic or gas as you drive. Wheel hubs with dry or damaged bearings lose unilateral movement while knuckle arm ball joints that are worn out or corroded will make crackling noises as the car drives or the suspension articulates.

Failure of any of these two components can make your wheels collapse or fall off. Delay to shift gears is a sign that you need to check automatic transmission fluid condition (level or quality) or presence of electrical or mechanical faults. A visit to the garage for inspection and diagnosis is necessary.

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Why does my car make a jolt when shifting to reverse?

I have an Audi A4 B7 (2007) 2.0L with automatic transmission. Of late, when I engage the reverse gear, especially in the morning, there is a slight jolt. What could be the problem?

Ronnie.

Hello Ronnie, the slight jolt during gear engagement on your Audi’s automatic transmission means something is faulty. You need a mechanic to inspect the car or carry out a computer diagnosis. Action to remedy the jolt should be taken before it develops into a more severe rough gear engagement or shifts.

There are a couple of potential causes of this problem including low or dirty automatic gearbox fluids, faulty or leaking torque convertor or faulty valve body and solenoids. If your car’s mileage is above or close to 100,000kms, consider replacing the gearbox oil and gearbox filter.

Since your Audi uses special transmission fluid, establish the correct oil grade and where to find it. A gearbox with dirty transmission fluid will suffer damage of the torque convertor, valve body and clutches. Restricted fluid movement due to a dirty filter causes rough gear engagement. Often aged leaking seals can reduce the transmission fluid levels and cause rough shifting.


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