12 Questions
What is the purpose of automatic transmission fluid (ATF)?
To lubricate bearings in the transmission
How many basic types of ATF are there?
Three
Why is it important to use the specified fluid for a transmission?
Different transmissions require different formulations of ATF
What is the function of an automatic transmission fluid cooler?
To prevent ATF from reaching high temperatures
How do automatic transmissions circulate ATF?
By using a pump
What is the purpose of a pressure regulator valve in a transmission?
To control hydraulic pressure
What is a variable displacement pump used for in newer automatic transmissions?
To reduce the power needed to achieve fluid pressure
What is the purpose of electronic pressure regulation in a transmission?
To control hydraulic system pressure regulation
What are apply devices or holding devices in a transmission?
Mechanical or hydraulic assemblies that provide the force to hold or drive members of a planetary gear set
What are transmission bands made of?
Cast iron or steel with friction material lining on the inside surface
What is the purpose of a hydraulic servo in a transmission?
To apply the band by using a hydraulically operated piston that travels inside a machined cylinder bore
How do multiple-plate hydraulic clutches differ from bands?
They can handle more torque than a band
Study Notes
- Automatic transmission fluid (ATF) is a refined oil designed for use in automatic transmissions.
- ATF transfers power in the torque converter, provides hydraulic pressure, lubricates bearings, and transfers heat to cool transmission parts.
- There are three basic types of ATF: non-friction modified, friction modified, and highly friction modified.
- Using the specified fluid is key to proper operation, as different transmissions require different formulations of ATF.
- The torque converter generates a lot of heat, which can cause ATF to reach high temperatures quickly, necessitating the use of an automatic transmission fluid cooler.
- Automatic transmissions use a pump to circulate ATF and provide necessary hydraulic flow.
- Transmission oil pumps are capable of creating excessive pressure, so a pressure regulator valve is used to control hydraulic pressure.
- Newer automatic transmissions use a variable displacement pump to reduce the power needed to achieve fluid pressure.
- Electronic pressure regulation allows for precise hydraulic system pressure regulation and can modify the timing and feel of transmission shifting.
- Apply devices or holding devices are mechanical or hydraulic assemblies that provide the force to hold or drive members of a planetary gear set, and include transmission bands, multiple-plate clutches, and one-way clutches.
- Transmission bands are holding devices, not capable of driving any member of the planetary gear set.
- Bands are made of cast iron or steel with friction material lining on the inside surface.
- There are two types of bands: single-wrap and double-wrap.
- Bands can be classified as either flexible or fixed.
- A hydraulic servo applies the band by using a hydraulically operated piston that travels inside a machined cylinder bore.
- A multiple-plate hydraulic clutch is a type of apply device that can handle more torque than a band.
- The plates of a multiple-plate clutch assembly consist of a friction plate alternated with steel plates.
- Clutches have more friction area so they can develop more force than a band, and they are self-adjusting.
- To apply the clutch, pressurized fluid enters the drum through an internal passage in the input shaft.
- To release the clutch, hydraulic fluid to the apply side of the piston is cut off and exhausted through an exhaust port.
Test your knowledge on the inner workings of automatic transmissions with our quiz! From the different types of automatic transmission fluid to the mechanics of apply devices like transmission bands and multiple-plate clutches, this quiz will challenge your understanding of the complex system that keeps your car moving smoothly. Keywords: automatic transmission, ATF, torque converter, hydraulic pressure, friction, apply devices, transmission bands, multiple-plate clutch.
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