Important: When you service the synchronizers, retain in order the components that you remove.

1. Clean all the parts in a suitable cleaning solvent. Air dry all the parts.
2. Inspect the synchronizer hubs for a force fit on the mainshaft. All of the hubs except for reverse gear synchronizer have a force fit.
3. Replace synchronizer hubs that due not require a force fit.
4. Inspect the synchronizer hub for wear on the external splines. A stepped effect on the teeth due to wear may cause shift problems.
5. Replace a worn hub.
6. Correct the cause such as but not limited to the following:

•	Engine related vibrations

•	Driving at a low speed in a high gear

•	Defective vibration damper or crankshaft

•	Incorrectly set injector pump




7. Measure the block to hub clearance.

•	The standard clearance between the block and the hub (2) is 0.1-0.35 mm (0.00393-0.01377 in).

•	The minimum clearance between the block and the hub is 0.5 mm (0.0196 in).

8. Inspect the shift block plungers (3) for wear or damage.
9. Inspect the shift block plunger springs for distortion.



10. Inspect the synchronizer sleeve teeth (1) for the following which may cause shift problems:

•	Grated teeth

•	Chipped off teeth

•	Blunted teeth

11. Inspect the synchronizer sleeve detent stops (2) for wear or being chipped off.
12. Replace the synchronizer assembly if the teeth or stops show the above conditions.



13. Inspect the synchronizer blocker rings for worn away grooves.
14. Replace the blocker ring assembly if the blocker ring grooves are worn away.



15. Inspect the synchronizer blocker rings for worn shift teeth.
16. Inspect the center ring for being warped or damaged.
17. Inspect the inner ring for worn grooves.
18. Inspect the 5th/6th synchronizer later plunger springs for distortion or wear.
19. Replace the synchronizer ring assembly for any of the above conditions.



20. Measure the blocker ring to gear clearance.

20.1.

Assemble the correct blocker ring to the correct gear.

20.2.

Apply pressure to the blocker ring to fully seat the ring.

20.3.

Using a feeler gage measure between the blocker ring teeth and the teeth on the gear.

•	The standard clearance between the 5th and 6th blocker and the gear is 2.0 mm (0.0787 in).

•	The minimum clearance between the 5th and 6th blocker and the gear is 0.0 mm (0.0 in).

•	The standard clearance between thew 2nd, 3rd, and 4th gear blocker ring and the gear is 2.0 mm (0.0787 in).

•	The minimum clearance between thew 2nd, 3rd, and 4th gear blocker ring and the gear is 0.0 mm (0.0 in).

21. If using a NEW blocker ring and the standard clearance can not be obtained replace the gear.