Chapter 14 Automatic Transmission Fundamentals

hypoid gears

Pinion type, instead of spiral bevel gears, allows lower contact point with ring gear, therefore lower car height. Also changes the axis of the input gear to the output gear 90 degrees.

sun gear

The central large gear in a planetary gear set

ring gear

The outer gear in a planetary gearset.

dual-clutch transmission

type of automatically shifting manual transmission in which two separate input shafts are connected to their own clutch. Shifting of the gears alternates between the two input shafts.

power-splitting transmission PST

type of hybrid transmission that splits the power flow going to the wheels from one or more sources.

fluid coupler

type of hydraulic coupling used on vintage vehicles to connect and transfer power from the engine to the transmission

coefficient of friction

value assigned to materials that describe the amount of friction when two objects slide against each other.

Thrust washer

A bronze or a hardened steel washer placed between two moving parts.

gasket

A compressible material placed between two surfaces to prevent leakage.

thrust bearing

Also called a torrington bearing, small flat roller bearing that almost resembles a flat washer.

gear ratio

The ratio of the speed of the driving member of a gear train to that of the driven member.

automatic transmission

Transmission that shifts automatically through the gears as the vehicle's speed increases

Continuously Variable Transmission

Transmission that uses a steel belt and sheaves to provide an endless amount of gear ratios.

Lock up converter

Type of torque converter that "becomes one" when the PCM energizes the TCC solenoid. During this state, there is no slipage between the engine rpm and the transmission input shaft.

Band

a metal device that wraps around a drum with friction material bonded to one side. This device squeezes the drum from rotating when the appropriate gear is selected.

extension housing

aluminum or cast iron enclosure for the transmission output shaft and bearings.

Overdrive

any gear ratio that results in torque reduction with increase in speed.

differential

component that allows power to flow to both wheels while allowing each wheel to go at different speeds such as during a cornering event.

planet carrier

device that holds planet gears in place keeping them equally spaced.

spur gear

gear that has straight cut gears

standard torque converter

hydraulic coupling device consisting of an impeller, turbine, stator, and housing. Connects the engine's power to the transmission

planetary gears

small gears that revolve around the sun gear.

Flex plate

steel plate that is thin and bolts to the crankshaft flywheel. Typically has a ring gear for the starter as part of its construction.

helical-cut gear

type of gear in which the teeth are cut in a spiral down the axis of the gear. This allows for one or more teeth to be in contact at all times and makes the gear stronger.

One-way Clutch (overrunning clutch)

type of holding device that stops the rotation of a component one way but allows for it to over run the other direction.

multi-disc clutch

type of holding device used by automatic transmissions to stop the movement of one component of a planetary gear set. It uses several thin friction discs and flat steel discs. When applied, all of these discs are squeezed into one solid unit.

series-parallel hybrid drive train

type of hybrid drive train that can function as both a series hybrid and a parallel hybrid

Parellel hybrid drive train

type of hybrid transmission in which power can flow from either a gasoline engine or an electric motor.

series hybrid drive train

type of hybrid transmission in which power flows from the engine through an electric motor. The electric motor supplements the power from the engine to the wheels.