Automatic Transmission
Ch 39
• 3 spd, 4 spd OD, 5, & 6 spd automatic.
• 4L60E - 4T60E
Torque Converter
• Operates by hydraulic force created by
transmission oil
• Between engine & trans. (filled w/ fluid)
• 3 Main parts
– Impeller
– stator
– turbine
• Converter multiplies twisting motion of
crank shaft
T/C operation
• Impeller-input member, receives power
from engine
• Turbine-output member, splined to
transmission
• Stator-reaction member or torque multiplier
– redirects fluid to enable torque multipication
• Pump drive hub-notches on converter shaft,
ground 180deg. apart
TCC valve reverses
fluid flow & causes the
piston to push against the
turbine and cover
Planetary gear sets are the way different gears rations are
achieved
Automatic transmission hold and input different combination
of these gear sets to achieve ratios
Rule to remember: external to external=direction change
external to internal =no direction change
T-39-1
pg1001
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Types of planetary gear sets
• Simpson gear set
– two gearsets share a common sun gear
– most commonly used (simpson gear train)
• Ravigneaux set
– two gear sets share a common ring gear
– more compact
– carries more load due to more tooth contact
Transmission Bands
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Band-braking assembly around a drum
takes up minimum space
creates self energizing action
paper (high speed) or metallic (low speed)
Single wrap or double wrap
Flexible (more self energized or Rigid (can
hold more)
Trans Clutch Discs
-Can hold or apply components
-Clutch hub holds all components; cylinder, piston,
piston return springs, seals, pressure plate, friction
linings, steel plates, & return springs.
-Friction linings are cellular paper,
graphite, & ceramic.
Bearings, Bushings, & thrust washers
Thrust washer - sliding bearing, made from copper,
bronze, teflon, or nylon. Used with low speeds & low
loads. Can be selective
Torrington bearing - has small rollers, used at high
speeds, & heavy loads. Can be selective
Seals
Static, dynamic, positive, non-positive
Lip Seals
-seals around moving parts
-spring & lip allow .0001 clearance
-rubber seals used for non moving parts
Ring Seals
-seal in excessive heat range
-when positive seal is not needed
-can be made from metal, teflon, or nylon
Hydraulics
• Pressure Regulating valves
– Changes fluid pressure
– changes shift feel & quality
• Flow directing valves
– direct fluid to appropriate apply devices
• Trans Cooler
– when fluid reaches 175 deg it varnishes
– fluid will break down & oxidize (hard on seals)
– cooler should be replaced or at least flushed
when rebuilding transmission
Hydraulics
Spool Valve