Manual Transmission and Transaxle Service

Walla Walla Community College

Automotive Technology

Lubricant

Lubricants fulfill these requirements:Lubrication of the gears

Reduction of friction and power loss

Protection against rust and corrosionCooling Bearings and Gears

Carrying away metal particles

Reduction of noise from gear box

Lubricant Types

Refined or synthetic oils

Chemical additive are added with base oil to produce extreme pressure (EP) lubricant.

High Viscosity (thickness)

SAE 75W to SAE 140

Multi-viscosity oil such as: 75W-90

Some use Synchromesh Transmission Fluid (STF)

Other specify Auto Trans Fluid (ATF)

Lubricant InspectionCheck at recommended intervals7500 to 30,000 milesSome manufacturers recommend fluid life of transmissionSome units have dip sticksSome use fill plugClean area around plug before checkLubricant Level must not be more than ½” below fill hole

Lubricant ReplacementDrive vehicle to warm fluid

Drain lubricantInspect fluid for metal particlesReplace fill plug washerTighten plug to specified torque

Some drain plugs are magnetizedInspect for metal chips, bronze chips, etc.

TRANSMISSION & TRANSAXLE

SERVICE

Diagnosing Problems

Service Manuals

Must locate exact source of problem

Some problems seem trans related but are caused by other area of the car

Verify customer concern – Always road test with customer if possible

Don’t guess at diagnosis with customer

Visual Inspection of Case

Check lubricant

Check gaskets and seals

Check case for porosity

Inspect mounts dynamically

Move clutch and shift linkages

Transaxle boots

CV Joints

Seals and Gaskets

Inspect for wear at the lip

Loss of flexibility

Shaft Oil SealsCan wear a groove in shaft

Extension housing seal

Good to just replace during service

Speedometer Drive Gear

Inspect for worn or stripped teeth

Inspect gear shaft o-rings

Gears are color coded for application

Shafts Inspect inside bearing races of main shaft and countershaft.

Some have needle bearings or bronze bushings

Shaft spline wear, Inspect for shoulders worn

Pilot Bushing wear

Output Shaft wear, especially the front

Gear Condition

Inspect wear marks on gear teeth facesPolished surfaces are normal

Chipped, cracked or broken teeth means replace

Gear Tooth Inspection

Shiny Surface in center of tooth

Minor imperfections acceptable

Coast side wear less important

Can file imperfections sometimes

Inspect Gears for Wear and Clearances

Gear Removal

Bearings and Thrust WashersBall Bearings must rotate smoothly

Account for all bearingsSome are not caged

Thrust WashersMark them on disassembly

Measure for thickness and record

Check Specifications for thickness

Thrust Bearing

Inspect for wear

Roll bearing and check for smoothness

Inpsect roller bearings for pits, scoring, etc.

Inspect race for wear

Synchronizers

Synchronizers hubs and sleeves are matched setIndex parts before disassemblyInspect bronze synchronizers rings for wear

BreaksBroken TeethWorn groovesBroken or missing keysSlide sleeve back and forth and check for smoothness

Synchronizer Components

Synchronizer Assembly

Inspect Blocking ring for sharp teeth

Measure wear of assembly

Snap Rings

Many different sizes

Special Snap Ring pliers

Don’t overstretch

Hidden Snap Rings

Assembling The Transmission

Use Shop manual for correct procedureSequence

Use micrometer, dial indicator or feeler gauge for clearancesUse chassis grease to hold bearingsMultiple thickness thrust washersSelective fit snap ringsObserve Torque specifications carefully

TRANSMISSION AND TRANSAXLE DIAGNOSIS

Transmission Noise

Verify noise is coming from transmissionTest Drive with customerProcess of eliminationNoises

Bearings – Will show up worse under loadGear teethSynchronizers – Gear clashNoise specific to a certain gear

Rough Growling Noise

Several possible problems

Neutral with engine runningInput shaft roller bearings

Vehicle movingInput and output shaft rotating

If forward or reverse but not neutral, possible output shaft bearings

Rough Growling Noises

Engine Running, clutch engaged, trans in neutralFront input shaft bearing at fault

If moving in all gear range noiseFaulty counter gear bearings

If all gears except direct driveRear input shaft bearing

Clicking or Knocking Noise

Possible Helical gear broken teeth

Chipped or broken teeth my cause other problems

Gear Clash

Grinding noise during shifting

Caused by one gear set remaining partly engaged while another gear set attempts to turn the main shaft

Incorrect Clutch Adjustment

Damaged, worn synchronizers

Improper lubricant

Hard ShiftingDifficult to move from gear to gear (especially under

load)Check Clutch AdjustmentCheck hydraulic system operationDamage inside the transExcessive wear on gear locking or clutching teeth

gearBadly worn bearingsDamaged shift linkage

Jumping out of GearIf when decelerating

Shift lever and internal gearshift linkage wear or misalignment

Excessive clearance between gears and input shaftBadly worn bearingsInternal components

Clutch pilot bearingGear teethShift forksShift railsSprings or detents

Locked in Gear

Gearshift linkage damaged or misadjusted

Low lubricant level

Worn support bearings

Using Service Manuals

Disassembly procedure

Specifications

Torque Specs

Special Tools