Manual Transmission and Transaxle Service

1. Manual Transmission and Transaxle Service Walla Walla Community College Automotive Technology

2. Lubricant • Lubricants fulfill these requirements: • Lubrication of the gears • Reduction of friction and power loss • Protection against rust and corrosion • Cooling Bearings and Gears • Carrying away metal particles • Reduction of noise from gear box

3. 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)

4. Lubricant Inspection • Check at recommended intervals • 7500 to 30,000 miles • Some manufacturers recommend fluid life of transmission • Some units have dip sticks • Some use fill plug • Clean area around plug before check • Lubricant Level must not be more than ½” below fill hole

5. Lubricant Replacement Drive vehicle to warm fluid • Drain lubricant • Inspect fluid for metal particles • Replace fill plug washer • Tighten plug to specified torque • Some drain plugs are magnetized • Inspect for metal chips, bronze chips, etc.

6. TRANSMISSION & TRANSAXLE SERVICE

7. 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

8. 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

9. Seals and Gaskets • Inspect for wear at the lip • Loss of flexibility • Shaft Oil Seals • Can wear a groove in shaft • Extension housing seal Good to just replace during service

10. Speedometer Drive Gear • Inspect for worn or stripped teeth • Inspect gear shaft o-rings • Gears are color coded for application

11. 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

12. Gear Condition • Inspect wear marks on gear teeth faces • Polished surfaces are normal • Chipped, cracked or broken teeth means replace

13. Gear Tooth Inspection • Shiny Surface in center of tooth • Minor imperfections acceptable • Coast side wear less important • Can file imperfections sometimes

14. Inspect Gears for Wear and Clearances

15. Gear Removal

16. Bearings and Thrust Washers • Ball Bearings must rotate smoothly • Account for all bearings • Some are not caged • Thrust Washers • Mark them on disassembly • Measure for thickness and record • Check Specifications for thickness

17. Thrust Bearing • Inspect for wear • Roll bearing and check for smoothness • Inpsect roller bearings for pits, scoring, etc. • Inspect race for wear

18. Synchronizers • Synchronizers hubs and sleeves are matched set • Index parts before disassembly • Inspect bronze synchronizers rings for wear • Breaks • Broken Teeth • Worn grooves • Broken or missing keys • Slide sleeve back and forth and check for smoothness

19. Synchronizer Components

20. Synchronizer Assembly • Inspect Blocking ring for sharp teeth • Measure wear of assembly

21. Snap Rings • Many different sizes • Special Snap Ring pliers • Don’t overstretch

22. Hidden Snap Rings

23. Assembling The Transmission • Use Shop manual for correct procedure • Sequence • Use micrometer, dial indicator or feeler gauge for clearances • Use chassis grease to hold bearings • Multiple thickness thrust washers • Selective fit snap rings • Observe Torque specifications carefully

24. TRANSMISSION AND TRANSAXLE DIAGNOSIS

25. Transmission Noise Verify noise is coming from transmission Test Drive with customer Process of elimination Noises Bearings – Will show up worse under load Gear teeth Synchronizers – Gear clash Noise specific to a certain gear

26. Rough Growling Noise Several possible problems Neutral with engine running Input shaft roller bearings Vehicle moving Input and output shaft rotating If forward or reverse but not neutral, possible output shaft bearings

27. Rough Growling Noises Engine Running, clutch engaged, trans in neutral Front input shaft bearing at fault If moving in all gear range noise Faulty counter gear bearings If all gears except direct drive Rear input shaft bearing

28. Clicking or Knocking Noise Possible Helical gear broken teeth Chipped or broken teeth my cause other problems

29. 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

30. Hard Shifting Difficult to move from gear to gear (especially under load) Check Clutch Adjustment Check hydraulic system operation Damage inside the trans Excessive wear on gear locking or clutching teeth gear Badly worn bearings Damaged shift linkage

31. Jumping out of Gear If when decelerating Shift lever and internal gearshift linkage wear or misalignment Excessive clearance between gears and input shaft Badly worn bearings Internal components Clutch pilot bearing Gear teeth Shift forks Shift rails Springs or detents

32. Locked in Gear Gearshift linkage damaged or misadjusted Low lubricant level Worn support bearings

33. Using Service Manuals Disassembly procedure Specifications Torque Specs Special Tools