Automotive Drivetrains
Purpose:
• Connect/disconnect engines power to
the drive wheel(s)
• allow for different speed ratios
• provide for reverse
• power control for safe turning
• torque multiplication
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Automotive Drivetrains
Components:
• Transmission
• Axle assembly
• Transaxle (fwd)
• Drive Shaft(s)
• related components
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Automotive Drivetrains
Engine torque:
• The turning effort of the
crankshaft
• measured in foot-pounds
• maximum torque is produced
within a narrow RPM range
(torque curve)
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Engine Torque
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Automotive Drivetrains
Horsepower
= work performed at the rate
at which it is being done
= torque X RPM / 5252
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Engine Horsepower
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Automotive Drivetrains
Gears
• Used to apply torque to other
rotating parts of the
drivetrain
• used to multiply torque in
automobiles
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Automotive Drivetrains
Gear Types
• Spur gear (most basic)
• Helical gear (helix = form a curve)
• Herringbone gear = 1 gear w/2 helical
gears w/teeth angles reversed
• Bevel gear - cone w/top cutoff
• hypoid gear - similar to above
• planetary gear(set)
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Automotive Drivetrains
Spur gear
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Automotive Drivetrains
Helical Gear
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Automotive Drivetrains
Straight Bevel Gearset
Gears must be perpendicular to each other
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Automotive Drivetrains
Spiral Bevel vs. Hypoid
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Automotive Drivetrains
Planetary Gear
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Automotive Drivetrains
Gear Measurements
• Backlash - the clearance between two
meshed gears
– measured with a dial indicator
• end play - axial or end-to-end
movement of a gear
– also measured with a dial indicator
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Torque Multiplication
Torque is calculated by
multiplying force X distance
OR
the center of the shaft
times (X)
the point where the force is
exerted
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Automotive Drivetrains
Gears Continued:
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Automotive Drivetrains
Gears continued:
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Automotive Drivetrains
As torque is
multiplied power
remains unchanged
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Automotive Drivetrains
Gear Ratios:
• The mathematical relationship of one gear
to another
• expresses the amount of torque
multiplication between two gears
• ratio = # of teeth of DRIVEN gear / # of
teeth of drive gear
- OR • ratio = outside diameter of DRIVEN gear/
O.D. of drive gear
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Automotive Drivetrains
Gear Reduction
= a reduction in the driven gears
speed
= an increase in the driven gears
torque
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Automotive Drivetrains
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Automotive Drivetrains
If the DRIVING gear in the previous
example is producing 250 ft.-lb. of
torque how much torque is the
DRIVEN gear producing?
4 X 250 =
1000 ft.-lb. torque
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Automotive Drivetrains
Bearings
• Used to attach a shaft to a
common component AND allow
for movement or rotation
• friction reduction
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Automotive Drivetrains
Bearing Types
• Bushing (simplest type) also called a
plain type bearing
• ball bearing - balls used for friction
reduction
• roller bearing
• tapered roller
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Bushing (simplest type) also
called a plain type bearing
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Ball Bearing
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Roller Bearing
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Needle Roller Bearing
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Tapered Roller Bearing
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Automotive Drivetrains
Bearing Usage
• radial or journal bearing
• thrust bearing
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Automotive Drivetrains
Bearing Measurements
• Bearing preload - the
amount of torque- load on a
bearing
– measured with a torque
wrench
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Automotive Drivetrains
The engine
produces torque
Torque is transferred to
the drive wheels through a
series of gears and shafts
CLUTCH
How do we
disconnect engine
power from the
drive wheels?
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