manual transmission diagnosis and repair
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Manual Transmission Diagnosis and Repair

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Manual Transmission Diagnosis and Repair. Chapter 72. Objectives. Diagnose transmission-related problems Remove a transmission safely in a professional manner Disassemble transmissions correctly Use presses and pullers competently to disassemble and reassemble transmissions

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Presentation Transcript
  • Diagnose transmission-related problems
  • Remove a transmission safely in a professional manner
  • Disassemble transmissions correctly
  • Use presses and pullers competently to disassemble and reassemble transmissions
  • Diagnose and service synchronizers
  • Reassemble and install a transmission in a vehicle
    • Important considerations in transmission repair
    • Proper press and puller use
    • Locating service information
  • Disassembling transmissions
    • Requires controlled force
    • Each transmission has its own peculiarities
    • Synchronizers are mostly of the same design
transmission diagnosis
Transmission Diagnosis
  • Clutch problem
    • Transmission doesn\'t go into gear
  • Transmission failure
    • Results from abuse or misapplication
    • Determine cause before removal
  • Some typical symptoms:
    • Gear clashing during shifting
    • Hard shifting and jumping out of gear
    • Unusual noise
lubricant checks
Lubricant Checks
  • Lubricant level
    • Checked by removing the fill plug and inserting your little finger inside the hole
  • Check for leaks
    • Front and rear seals
    • Any switches
    • Plug or vents
    • Gaskets
  • Oil leakage can result in transmission failure
transmission removal
Transmission Removal
  • Major steps
    • Removing a transmission can be dangerous
      • Drain gear oil before installing jack
      • May be necessary to remove exhaust pipes
    • Disconnect battery
    • Remove speedometer cable
    • Disconnect external shift linkage
    • Remove and clean transmission
      • Identify transmission before ordering parts
transmission disassembly
Transmission Disassembly
  • Major steps
    • Check service manual before disassembling
    • Look for damage
      • Gears develop normal wear pattern with use
    • Remove front bearing retainer and snap rings
    • Remove countershaft and mainshaft
      • Mainshaft removed from rear or top of transmission
    • Remove the input shaft
      • Be careful not to damage gears
disassemble the mainshaft assembly
Disassemble the Mainshaft Assembly
  • Major steps
    • Lay parts out as they are disassembled
      • Keep parts in order
    • High-gear synchro clutch hub
      • Held on mainshaft with a snap ring
      • Remove snap ring with snap ring pliers
    • Press or puller pulls synchronizer clutch hub
synchronizer service
Synchronizer Service
  • Synchronizer will be reused
    • Scribe line on outside to reassemble in same position
      • Some are marked from factory
  • Look for wear
    • Gears and shift sleeves
synchronizer inspection
Synchronizer Inspection
  • Best way to tell if synchro is not working
    • Test-drive the vehicle
  • Worn synchro
    • Causes gear clashing
  • Inspect synchronized gears
    • Rarely experience excessive wear
  • Inspect synchro sleeve
    • Even width across length
inspect blocker rings
Inspect Blocker Rings
  • Inspect brass blocker rings if they are to be reused
    • Inside surface should have sharp edges
  • Push blocker ring against polished tapered surface on gear that it rides on
    • Should grab against chrome surface
inspect input shaft and mainshaft
Inspect Input Shaft and Mainshaft
  • Inspect mainshaft splines
    • May be twisted from abusive driving
    • Twisted spline prevents drive shaft slip yoke from sliding in and out of transmission
  • Inspect drive gear for VSS or speedometer
    • Located on the output shaft
    • Rarely suffers damage
    • A special puller is available to pull these gears
replace worn bearings
Replace Worn Bearings
  • Use a press and support inside of bearing with bearing separator
    • Reassembling: apply pressure on inside of bearing only
reassemble the transmission
Reassemble the Transmission
  • Before assembling
    • Locate and assemble any new replacement parts
  • Two gears operating in mesh
    • Create wear pattern
  • Gear is replaced
    • Corresponding gear also replaced
    • Using an old gear with a new gear can result in unacceptable gear noise
reassemble the synchronizers
Reassemble the Synchronizers
  • Reassemble synchronizer hub parts
    • Three inserts are held in place with a round spring
  • Install springs so they rotate in opposite directions
reassemble the mainshaft
Reassemble the Mainshaft
  • Major steps
    • Install gears
    • Lubricate parts liberally
    • Install synchro hub
    • Check end play of assembled parts
end play
End Play
  • Thrust washers
    • Control end clearance
    • Determine where gear will be positioned
  • Check gear clearance after all gears are assembled
    • Adjust clearance by changing thickness of snap ring
needle bearing installation
Needle Bearing Installation
  • Needle bearings are sometimes caged
    • Can also be loose and installed one at a time
    • Count needle bearings during disassembly
  • Service manual
    • Specifies number of needle bearings
install new gaskets
Install New Gaskets
  • Purchase a new transmission gasket set
    • Gaskets are not reusable
  • Gasket working fine previously could leak after reassembly
    • Replacing this gasket would be a complicated repair
      • Would be done at no charge to the customer
complete the transmission reassembly
Complete the Transmission Reassembly
  • Install shift mechanism
  • Replace extension housing bushing and seal
    • Use a seal installer to replace the seal without distorting it
install the transmission
Install the Transmission
  • Major steps
    • Be sure clutch fork is properly seated on its pivot
    • Align transmission with engine
    • Shake transmission while rotating it back and forth
    • Install bolts in transmission
    • Torque to specifications
add lubricant
Add Lubricant
  • Important considerations
    • Add recommended lubricant before driving the vehicle
    • Lubricant level should come to bottom of fill hole
test drive
Test Drive
  • Important considerations
    • Be sure shifts are smooth in all gears
    • Neutral gate should be accurately aligned
    • Check outside of transmission for leaks after returning to shop