Main Components and Functions

Main Components and Functions

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Transmission Main Components-Sectional View

Torque Converter
The torque converter transmits and multiplies torque. The torque converter is a four-element device:
^ impeller assembly
^ turbine assembly
^ reactor assembly
^ clutch and damper assembly





The standard torque converter components operate as follows:
^ Rotation of the converter housing and impeller set the fluid in motion.
^ The turbine reacts to the fluid motion from the impeller, transferring rotation to the geartrain through the input shaft.
^ The reactor redirects fluid going back into the impeller, allowing for torque multiplication.
^ The clutch and damper assembly dampens powertrain torsional vibration and provides a direct mechanical connection for improved efficiency.
^ Power is transmitted from the torque converter to the planetary gearsets and other components through the input shaft,

Geartrain
Power is transmitted from the torque converter to the Ravigneaux geartrain components through the input shaft and forward clutch cylinder.
^ The geartrain contains a Ravigneaux planetary set connected by dual pinion gears.
^ By holding or driving certain components of the gearset, four forward ratios and one reverse ratio are obtained and transmitted to the output shaft. The ratios are as follows:





^ Components of the geartrain can be held by bands or clutches and driven by clutches only.

The 4R70W uses:
^ two bands.
^ two one-way clutches (one roller, one mechanical diode).
^ tour friction clutches.

Planetary Gearset
The planetary gearset in the transmission is a Ravigneaux-type set consisting of the following components:
^ forward clutch sun gear
^ reverse clutch sun gear
^ a pinion carrier
^ long and short pinions
^ output ring gear

Components are held or driven to produce forward and reverse gear ratios.

Input Shaft
The forward clutch cylinder and shaft transfers speed and torque from the converter turbine to the geartrain. This shaft is splined to the turbine on one end and to the forward clutch sun gear and stub shaft on the other end.

Stub Shaft
The stub shaft transfers power from the input shaft to the planet carrier (through the direct clutch) during third and fourth gear operation.

Output Shaft
The output shaft provides torque to the driveshaft and rear axle assembly. It is driven by the ring gear of the planetary gearset.

Apply Components
There are eight apply components used to drive or hold the planetary gearset components.





Band-Overdrive
The overdrive band holds the reverse clutch drum stationary in fourth gear and manual 2. This action causes the reverse sun gear to be held in these ranges.





Band-Low and Reverse
The low and reverse band holds the pinion carrier in reverse. The reverse band also applies in manual 1 position to provide engine braking.

Clutch-Intermediate





Intermediate Clutch Disassembled View
The intermediate clutch works with the intermediate one-way clutch to hold the reverse sun gear stationary in second gear. The intermediate clutch remains applied in third and fourth gears, but does not transmit power.

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Clutch-Forward
The forward clutch couples the forward clutch cylinder and input shaft to the forward sun gear in first, second, and third gears. The forward clutch is not applied in fourth gear.

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Clutch-Direct
The direct clutch couples the input shaft to the planet carrier through the stub shaft in third and fourth gears.

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Clutch-Reverse
The reverse clutch couples the input shaft to the reverse sun gear, applied in reverse range only.





One-Way Clutch-Planetary (Low)
The planetary (low) one-way clutch is a roller clutch that holds the planetary gearset in first gear, (D) and D ranges. During automatic coasting downshifts into first gear ((D) and D ranges), the planetary one-way clutch freewheels so there is no engine braking.





One-Way Clutch-Intermediate
The intermediate one-way clutch works with the intermediate friction clutch to hold the reverse clutch drum and reverse sun gear stationary in second gear during acceleration. The intermediate one-way clutch freewheels in third gear and during coasting in second gear, (D) and D ranges.

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Hydraulic System





Fluid Pump
The transmission uses a gerotor-type design front pump support and gear. The pump provides the volume of fluid needed to charge the torque converter, main control assembly, cooling system and lube system. Pump pressure is regulated by the main regulator valve. The pump has an internal boost circuit which is more efficient at lower engine speeds.

Filter
All fluid drawn from the transmission pan by the pump passes through the filter. The filter and its accompanying seal are part of the fluid path from the sump (pan) to the fluid pump.





Main Control
The main control valve body houses three electronic solenoids:
^ two shift solenoids
^ one Torque Converter Clutch Solenoid (TCC solenoid)

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Accumulators
The transmission uses two accumulators:
^ 1-2 Accumulator-The 1-2 accumulator is used to soften the 1-2 shift by absorbing some of the pressure directed to the intermediate clutch. Constant line pressure is applied to the middle section of the 1-2 accumulator piston, opposing the intermediate clutch pressure, until the pressure is high enough to overcome line pressure. The top of the piston is exhausted to the sump.
^ 2-3 Accumulator-The 2-3 accumulator is used to soften the 2-3 shift by absorbing some of the direct clutch pressure. Forward clutch pressure is applied to the top side of the 2-3 accumulator piston, holding the piston down until clutch pressure is high enough to overcome it. The middle section of the piston is exhausted to the sump.