Automatic transmission service is maintenance that is often ignored. Automatic transmission service intervals will vary across different makes and models and is also affected by how the vehicle is driven. If your car has a manual transmission, you need a clutch to smoothly engage a revving engine to a non-spinning transmission by controlling the slippage between them. A clutch works because of friction between a clutch plate and a flywheel and the clutch consists of several components that are all reliant on each other for smooth operation.
Automatic transmissions provide the level of precision needed to convert your engine’s power and torque to be redistributed for different purposes including reversing, towing trailers, highway driving and city driving. As your engine operates at various RPM (revolutions per minute) ranges, the transmission’s gear ratios are determined when certain gears are set in motion while other gears are made to remain stationary. Gears vary in size, positions and configuration to make the most of their interlocking teeth and allow the engine’s power to be directed to changing the direction the car moves in, synchronizing wheel rotations, the car’s weight distribution, and wheel-speed rotations.
Modern automatic transmissions are electronically controlled and have sensors within the transmission that monitor everything from vehicle speed to engine load and accelerator pedal position. The information these sensors provide is used by a computer to manage the gear shifting process.
Common symptoms of gearbox problems include:
– Hard to select gears
– Crunching noise when changing gears
– Stuck in gear
– Unable to select any or all gears
Manual transmissions and clutches are used to transmit energy from one mechanical device to another. The gearbox varies the speed of motion of the vehicle through increasing or decreasing torque through the utilisation of different size gears. This, in turn, changes the speed at the wheels through reducing or increasing the number of times the driveshafts turn in relation to engine speed.
A differential unit (commonly known as a ‘diff unit’ or just ‘diff’) has three main functions:
– Assist with transferring power to the wheels.
– Provide the final drive gear ratio of your car.
– Enable the wheels to turn at different speeds while cornering.
Common differential problems include:
– Whirring noise while decelerating at any or all speeds.
– Whining noise while accelerating between certain speed ranges, e.g. between 80kmph and 90 kmph.
– Rumbling noises as you increase speed which changes while turning
– A clunking or clanging noise every few metres. When cornering a clunking noise occurs.
There are different driveshaft configurations for front wheel drive, rear wheel drive and all wheel drive vehicles. A drive shafts primary purpose is to transmit torque and rotation between the transmission and the wheels.
CV joints or (constant velocity joints) are used on front wheel drive and vehicles with independent rear suspension whether they are rear wheel drive or all-wheel drive. CV joints allow a rotating shaft to transmit power through a variable angle, at a constant rotational speed.
Driveshafts in rear wheel drive vehicles are commonly known as tail shafts and connect the transmission to the differential unit. There are usually universal joints or rubber couplings at each end of the tail shaft that allows the tail shaft to change angles in line with suspension movement. Common CV joint and drive shaft problems: Clicking or knocking noise when cornering Clunking noise on deceleration and acceleration Vibrations through the car while driving.
Common clutch problems include:
– Gears grinding or crunching due to failure of the clutch to release properly when pressed.
– The Excessive force required to press the clutch pedal.
– The clutch slips which creates the sensation of the engine revving very high but the car failing to accelerate normally.
– The car shudders as the clutch pedal is released.
– Clutches also require an operating mechanism between the clutch pedal and the clutch fork which the release bearing is mounted to. This can either be done hydraulically or via a cable. Clutch hydraulic systems consist of a clutch master cylinder and a clutch slave cylinder and lines that carry fluid between them.
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