- A) Gear lever with multifunction switch. The position of the transmission control lever affects the activation of the reversing lights, the starter lock when the speed is on, as well as the operation of the speed control device (see illustration 4.0).
- b) Driving mode switch.
- V) Throttle angle potentiometer. The information from this sensor is used to calculate the gear ratio.
- G) The speed sensor mounted on the gearbox is also designed to determine the gear ratio. When this sensor fails, the control unit, as an emergency program, is guided by the number of engine revolutions received from the Hall sensor related to the ignition system.
- d) Cable kickdown switch «gas». It turns on when the accelerator pedal is pressed all the way down. The gearbox either stays longer in a lower gear position or shifts from a higher gear to a lower gear.
- and) The brake light switch releases the transmission control lever lock. Only when the brake pedal is depressed can the automatic transmission lever be moved from the position «R» or «N» into gear to continue driving.
- h) Automatic transmission fluid temperature sensor. A significant difference in speed between the engine and gearbox can lead to a strong increase in fluid temperature. When the electronic control unit receives information about an increase in fluid temperature, the upshift is performed with deceleration.
4.0 Scheme of operation of an automatic transmission
1 - gearshift unit
2 - automatic transmission control lever
3 - multifunction switch
4 - electronic control unit
5 - pusher
The electronic control unit recognizes and registers malfunctions and malfunctions in the automatic transmission. The self-diagnostic program monitors the input and output signals of almost all sensors or transmission components or their electrical circuits. Reading out and printing out faults is only possible in a workshop that has the appropriate instrument.
As soon as the electronic control unit has determined the presence of a malfunction that significantly affects the operation" automatic transmission, or if the unit itself fails, then the so-called emergency program is executed, consisting of two subroutines:
- A) An automatic upshift or downshift subroutine that ensures the gearbox operates in the same mode. When executing this program, jerks will be felt in the operation of the box.
- b) A subroutine that excludes automatic upshifting or downshifting of the gearbox. With this program, only 3rd gear will work when the control lever is in positions D, 3 and 2. And only in positions 1 or R will the gearbox still work.
When executing the emergency program, it is recommended to immediately contact the nearest workshop, where the self-diagnosis system will first be polled.
The range of work that the car owner is able to perform on an automatic transmission on their own is limited. However, targeted inspections can help in identifying faults, which is very important for used vehicles. With any transmission failure, the first thing to check is the fluid level in the transmission. If a burning smell is felt when removing the dipstick, then there is a very complex defect in the disc brake of an automatic transmission.
During a test drive, you can check the gearshift. When shifting to a higher gear with the accelerator pedal partially depressed, the gear change is almost not felt. When the pedal is in position «Full throttle» or when the mode is turned on «kickdown» gear changes are perceived more clearly, but the transition is smooth. A sharp increase in speed when changing from one gear to a higher one indicates the presence of a defect that should be established.
When shifting from higher gears to lower gears, the transition is practically not felt, especially if the speed was not very high. A jerk when pressing the accelerator pedal to increase speed is normal. Switching using the gearbox control lever occurs when the accelerator pedal is not pressed for 1-2 seconds, and when pressed, immediately.
Attention! An AUDI 80 with automatic transmission must not be towed under its own power for more than 50 km. It has to do with gearbox lubrication. The maximum towing speed must also not exceed 50 km/h. It is recommended to transport such vehicles by loading method.
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