Manual Transmission Diagnosis and Repair

1. Manual Transmission Diagnosis and Repair Chapter 72

2. 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 Diagnose and service synchronizers Reassemble and install a transmission in a vehicle

3. Introduction 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

12. 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

13. 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

14. Replace Worn Bearings Use a press and support inside of bearing with bearing separator Reassembling: apply pressure on inside of bearing only

15. 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

16. 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

17. Reassemble the Mainshaft Major steps Install gears Lubricate parts liberally Install synchro hub Check end play of assembled parts

18. 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

19. 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

20. 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

21. Complete the Transmission Reassembly Install shift mechanism Replace extension housing bushing and seal Use a seal installer to replace the seal without distorting it

22. 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

23. Add Lubricant Important considerations Add recommended lubricant before driving the vehicle Lubricant level should come to bottom of fill hole

24. 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