Note: 4 and 5 speed gearboxes have many very similar components. Minor differences are not affected in the described procedure.
1. Remove the circlip from the end of the shaft (photo), remove the thrust washer (photo). Note that the thrust washer is not installed on later transmissions.
2. Raise the 4th gear with needle bearing (photo). If the bearing is removed from the gear, paint the bearing and gear so that they can be reassembled in their original form.
3. Remove the 4th gear synchronizer ring.
4. Remove the retaining ring securing the synchronizer hub, remove the hub from the shaft (photo).
5. Remove the 3rd gear synchronizer ring, 3rd gear and needle bearing (photo).
6. Mark the gear and bearing so that they can be assembled correctly.
7. Before assembly, make sure all parts are clean and check their condition. Gearbox components are very expensive, if any gears or shafts need to be replaced, it may be more cost effective to install a different gearbox.
8. Lubricate the needles. bearing 3rd gear, install it on the shaft.
9. Install the 3rd gear.
10. If the synchronizer has been disassembled, look for marks on the outer edge. If they are, the hub must be inserted according to these marks. Later models are unmarked and are not re-installed.
11. Install three locking keys in the hub before installing the bushing, secure the keys with springs, the location of the springs is shown in fig. 6.4, the springs are installed with the angled end into the hole of the blocking nut.
12. Install the 3rd gear synchronizer ring on the gear cone, measure the gap with a feeler gauge (A) (Pic. 6.5). This gap must not exceed the value given in the Specifications, otherwise a new synchronizer ring must be installed.
13. Notice that the grooves in the synchronizer hub bore are grooved at one end. The hub also has an extra groove on one end (Pic. 6.6) and these surfaces must face the 4th gear.
14. Place the synchronizer onto the shaft by turning the 3rd gear synchronizer ring so that the grooves on it are aligned with the synchronizer lock crackers.
15. Insert snap ring on top of synchronizer hub, press synchronizer back against snap ring. This increases the gap between the synchronizer and the 3rd gear, which guarantees better bearing lubrication.
16. Install the 4th gear synchronizer ring, aligning the grooves in it with the synchronizer lock crackers, check the play as described in paragraph 12.
17. Install the 4th gear and bearing, lubricate them with oil, install the thrust washer (early models) and finally the retaining ring.
18. On early models, measure the end clearance between the 4th gear and the thrust washer. It must be at least 0.10 mm but less than 0.40 mm. If the clearance exceeds the upper limit, install a thicker thrust washer, the washers are available in three thicknesses: 3.47mm, 3.57mm and 3.67mm.
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