Isuzu M-150 (77.5 mm) 4-Speed

1. Disconnect retaining springs from bearing side and remove bearing, boot, and clutch fork.





2. Drain transmission, then remove bearing retainer bolts, retainer, gasket, and ball stud.

3. Remove speedometer driven gear, back-up light switch, shift cover retaining bolts, shift cover, and gasket.

4. Remove rear extension retaining bolts, rear extension, and gasket.





5. Remove speedometer driven gear from mainshaft.

6. Using suitable tool, drive pin from reverse shift block while supporting shaft end with bar or block of wood.





7. Remove reverse block retaining bolts and remove reverse shifter shaft, shift block, shift fork, and reverse gear as an assembly.





8. Remove retaining ring from drive gear shaft bearing outer race, then remove retaining ring from countershaft front bearing outer race.

9. Remove center support assembly from transmission case, being careful not to hit front end of drive gear shaft while removing transmission case.





10. Using suitable tool, drive pins from 1st/2nd & 3rd/4th shift forks while supporting ends of shafts with bar or block of wood.

11. Loosen retaining bolts and remove plate, gasket, and springs.

12. Place the three shifter shafts in neutral position and remove reverse shifter shaft, 1st/2nd shifter shaft, and 3rd/4th shifter shaft in that order, being careful not to lose interlock pins or detent balls.

13. Remove three detent balls, two interlock pins, and shift forks.

14. Engage synchronizers to prevent rotation of mainshaft and temporarily install transmission case to center support.





15. Using suitable tool, raise staking on mainshaft rear nut and remove nut, then remove reverse gear from mainshaft.

16. Remove nut, spring washer, plain washer, and reverse gear from countershaft, then remove case from center support.





17. Place synchronizers in neutral positions, then remove rear bearing retainer from center support.





18. Slide rear bearing outer race rearward by moving countershaft fore and aft and, using suitable tool, remove outer race.

19. Remove countershaft and drive gear shaft, then remove 4th blocker ring and needle roller bearing.