Manual Transmission Repair

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Manual Transmission Repair
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General Disassembly Procedures

• Refer to the appropriate service manuals for
  detailed disassembly procedures
• Check end play and clearances before disassembly
• Check detent springs and balls as they are
  removed
• They MUST be replaced correctly
• If force is required for disassembly use a soft
  faced hammer
• Mark and remove all synchronizers as an assembly
  and keep the together
• Including blocking rings
• Be careful not to loose parts
• Snap rings
• Needle bearings
• Thrust washers
• Spacers
• Detent balls
• springs

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Gear Failure Analysis

• Look for the following failure modes when
  inspecting gears
• Cracking
• Galling
• Spalling
• Pitting
• Wear

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Cracking
Elecon Engineering

• Causes
• Excessive loads
• Excessive backlash

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Galling

• Definition
• Galling is a condition in which two surfaces cold
  weld themselves together under high loads, then
  are torn apart transferring bits of metal from
  one surface to another

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Pitting
Generally caused by overload conditions
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Spalling

• Next step after pitting

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Wear

• Metal is worn away from the normal contact area
  of the gear
• Different levels of wear
• Polishing
• Moderate wear
• Extreme wear
• Abrasive wear

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Moderate Wear
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Abrasive Wear

• Caused by abrasive particles in the lubricant

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Inspection

• Input shaft
• Examine splines for smoothness and rust
• Inspect input gear for excessive wear, galling,
  pitting or chipping
• Check clutch teeth for wear
• Shift cone must be smooth and not scored
• Replace front seal
• Check pocket bearing surface

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Inspection

• Extension housing
• Check bushings for wear
• Replace seal
• Inspecting main shaft and gears
• Inspect bearing surfaces
• Check all teeth for chipping, galling or wear
• Check pocket bearing surface
• All snap ring grooves must have sharp square
  shoulders
• Thrust washers must be smooth and OEM specs for
  thickness
• Check driveshaft yoke splines for wear
• Check shaft for runout
• Use V-blocks and a dial indicator
• Check against OEM specs Normally not to exceed
  .002

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Inspection

• Countershaft and gears
• Check teeth for wear, pits, or cracks
• Check needle bearings
• Check thrust washers or spacers for wear or
  damage
• Reverse idler gear
• Check idler gear bushing or needle bearings
• Check thrust washers
• Check gear teeth

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Inspection

• Synchronizers
• Mark blocking ring and hub and return to the
  original position
• Check spings and inserts for wear
• Inspect hub inner splines
• Sleeve clutch teeth must not be battered or
  tapered
• Inspect blocking rings
• Inner teeth must be sharp
• Paper type must not show excessive wear

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Inspection

• Case
• Check for cracks and porosity (aluminum)
• Check all mating surfaces for burrs, dents, or
  warpage

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General Reassembly

• Always compare replacement parts to original for
  design, size and shape
• Make sure it fits properly
• Use new snap rings, thrust washers, seals, and
  gaskets
• Apply sealer to pins or shafts which pass through
  the case to prevent leaks
• Prelube all bushings shafts and gears with the
  appropriate lubricant
• Any assembly lube/grease must be compatible with
  and dissolve in the oil being used in the
  transmission
• Dummy shaft may be require to hold needle
  bearings in place during assembly
• Ensure shift forks are properly engaged into the
  synchronizer clutch sleeves
• Check transmission for ease of shaft rotation and
  shifting action