Limited Slip Differential

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Limited Slip Differential

• MAE442
• Dr. Klang
• David Starnes Technical Specialist
• Matt Barbeau Design Specialist
• William Morrison Team Management Specialist

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Outline

• Introduction
• History
• Types of Differentials
• -Conventional/Open Differential
• -Clutch Type Limited Slip Differential
• -Viscous Type Limited Slip Differential
• -Double Reduction Differential
• -Automatic and Manual Locking
• Dissassembled Differential Pictures

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Introduction

• Limited Slip Differentials (LSD) can be found on
  most modern cars and trucks.
• Helps prevent the wind up phenomenon.
• Varying types of differentials depending on the
  application.

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History

• Early use of the differential was to track the
  phase of the moon.
• 1st century BC- The Antikythera mechanism
  contains a planer differential. This device was
  found in a shipwreck just outside of the city of
  Crete.
• 1827- Watchmaker Onésiphore Pecqueur patented the
  modern automobile differential.

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History cont.

• 1832 - Richard Roberts of England patents gear
  of compensation for road locomotives.
• 1876 - James Starley invents the chain driven
  differential for bicycles.
• 1897 David Shearer uses the first automotive
  differential on an Australian steam car.

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History cont

• 1950-1960 Many manufactures began to apply
  brand names to their limited slip differential
  units. The most famous was Chevrolets
  Positraction.
• 1997- The first active differential was used in a
  production car it was found in the Honda Prelude
  SH and was called the Active Torque System.
• 2005 A fully integrated active differential is
  used on the MR Farri F430.
  A similar system is also used on the
  Acura RL.

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Conventional/Open Differential

• Consists of two side gears inside of the
  differential case.
• Found standard on most cars and SUVs
• All of the gears found inside of the differential
  case are directly connected to a shaft which is
  pinned into the case.

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Conventional/Open Differential cont

• Advantages
• Great on paved roads
• Predictable power distribution on dry surfaces
• Easy to drive and handle
• Simplicity of design
• Lower maintenance costs

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Conventional/Open Differential cont

• Disadvantages
• Poor off-road handling
• Unpredictable power distribution on lower
  friction surfaces, such as sand or mud
• Does not work if one of the wheels in the set is
  suspended in the air.

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Clutch Type LSD
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Clutch Type LSD cont.

• In this clutch type, there is a built in clutch
  preload
• The amount of preload determines how much
  tractive force will be transferred to the
  opposite tire during low speed operation.
• As load the applied increases, the separation
  forces between the spider gears and the side
  gears increase the clutch loading.
• Therefore, the amount of preload is a critical
  design factor in low speed operation.

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Viscous Type Limited Slip

• Advantages
• Smooth torque transfer
• Limited wind up at low speed
• More proportional response due to slip
• Easy to drive

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Viscous Type Limited Slip cont.

• Disadvantages
• Fluid can break down with time
• Less efficient than a conventional differential
• Higher associated maintenance

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Double Reduction Differentials

• Advantages
• Great for industrial purposes
• High output torque
• Relatively non-complex

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Double Reduction Differentials cont

• Disadvantages
• Lower mechanical efficiency
• Not good for lightweight vehicles
• Not the most adaptive design

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Automatic and Manual Locking

• Advantages
• Good for off road purposes
• Can be turned on and off according to driver
  preference
• Can save a driver the expense of always using
  four-wheel drive
• Higher efficiency compared to a viscous
  differential

• Disadvantages
• Either on or off, no in between
• The manual locking differential may only be
  turned on when the car is at rest
• Not good for unpredictable road conditions

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Pictures of Differential Disassembly

• Taken from a 1995 Dodge Stealth VR4.
• Car was used for drag racing with heavy loads on
  the differential.
• No damage to differential, showing ruggedness of
  design

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Reference Web Sites

• http//media.popularmechanics.com/images/vcoupling
  -sm.jpg
• www.autozine.org/technical_school/traction/tech_pi
  c_traction_diff_lock.jpg
• http//www.4wdonline.com/A/PiCs37/diff.jpg
• http//chevy.tocmp.com/1942_47shop/files/4247csm42
  2c.jpg
• http//www.autozine.org/technical_school/traction/
  tech_pic_traction_viscous_2.jpg