INTRODUCTION - 6 SPEED GEARBOX

1.4 16v

CONSTRUCTION SPECIFICATIONS

The structure of the gearbox consists of:

• a gearbox casing containing and supporting the main and layshafts, the gear engagement forks and rods and the gear selector/engagement device;
• the rear cover which contains the 5^th and 6^th speed gears and the bearing retaining plate for the main and layshafts;
• a casing joining the gearbox to the engine, containing the clutch, the thrust bearing and the control linkage.

1. Thrust bearing

2. Main shaft

3. Satellite gears

4. Planet gears

5. Toothed ring gear

6. 1^st speed driven gear

7. 2^nd speed driven gear

8. Gearbox casing

9. 3^rd speed driven gear

10. 4^th speed driven gear

11. Rear bearing retaining plate

12 - 5^th speed driven gear

13. 6^th speed driven gear

14. Layshaft

15. Rear cover

16. 6^th speed driven gear

17. Gearbox bell housing

Main shaft

The main shaft consists of:

• gears for 1^st and 2^nd speeds and reverse formed directly on the shaft;
• gears for 3^rd, 4^th and 5^th speeds fitted on the shaft.

The main shaft is supported by a front roller bearing and a rear ball bearing.

1. Reverse gear

2. Reverse shaft

3. Oil seal

4. Main shaft front mounting ball bearing

5. Main shaft

6. 1^st speed gear (formed on the shaft)

7. Reverse gear (formed on the shaft)

8. 2^nd speed gear (formed on the shaft)

9. 3^rd speed driven gear

10. 3^rd speed synchroniser ring

11. Presynchronisation block

12. 3^rd - 4^th speed synchronizer hub

13. 3^rd - 4^th speed synchronizer sleeve

14. 4^th speed synchroniser ring

15. 4^th speed driven gear

16. Main shaft rear mounting ball bearing

17. 5^th speed meshing bush

18. 5^th speed driven gear

19. 5^th speed synchroniser ring

20. 5^th speed synchroniser sleeve

21. 5^th - 6th speed synchroniser hub

22. 6^th speed synchroniser ring

23. 6^th speed driven gear

24. 6^th speed meshing bush

25. Roller bearing

26. Nut securing the gears

Layshaft

The layshaft consists of:

• 1^st, 2^nd, 3^rd, 4^th, 5^th and 6^th speed gears fitted on the shaft.

The layshaft mounting consists of:

• a front roller bearing
• a rear ball bearing.

1. Layshaft

2. Layshaft front mounting ball bearing

3. Needle cage

4. 1^st speed driven gear

5. 1^st speed synchroniser rings

6. Presynchronisation block

7. 1^st - 2^nd speed synchronizer hub

8. 1^st - 2^nd speed synchronizer sleeve

9. 2^nd speed synchroniser rings

10. 2^nd speed driven gear

11. 3^rd speed driven gear

12. Spacer

13. 4^th speed driven gear

14. Layshaft rear mounting ball bearing

15. 5^th speed driven gear

16. Spacer

17. 6^th speed driven gear

18. Ball bearing

19. Nut securing the gears

Gears

The gears are the following type:

• helical toothed for the forward gears
• straight toothed for reverse gear.

The teeth for all the gears are HCR (High Contact Ratio).

The 2^nd and 5^th speed and final drive gears are superfinished after the thermal treatment to guarantee absolute precision for the teeth, as well as quiet operation.

The gears and drive chain components inside the gearbox are lubricated dynamically, by means of the oil flowing along channels and through ports in the casings, the 3rd/4th speed rod and the main shaft. This allows:

• improved torque transmission and greater efficiency against the effects of wear
• manoeuvrability even at low temperatures thanks to the use of synthetic multigrade oil.

Synchronisers

The synchronisers for the forward speeds are Borg-Warner.

The layout for the synchronizers is known as the split type, where the synchronizers for 1^st and 2^nd speeds are fitted on the layshaft, whilst those for 3^rd, 4^th, 5^th and 6^th speeds are on the main shaft.

This solution reduces gearbox noise when parked in neutral because 3 of the 6 pairs of gears are not driven.

The engagement and synchronization loads are also reduced as a result of the corresponding reduction in the inert rotating masses downstream of the crankshaft.

The synchronizer on 1^st and 2^nd speeds, (the gears that are most used by the customer and thus subject to the most stress) is a double cone requiring far less engagement force than for a conventional single cone synchronizer of the same size (- 40%).

A new pre-synchronizer system comprising thrust bearing blocks is used on all the gears for smoother, more positive gear shifts: in 1^st and 2^nd speeds the sliding gears are supported by a needle cage. The geometry of the reverse gear teeth has been improved to guarantee excellent manoeuvrability and rapid and precise engagement.

Differential

The differential unit is located in the rear part of the gearbox casing.

It comprises:

• a reduction cylinder pair
• a differential housing in a single piece which incorporates the planet and satellite gears.

The differential is supported by two taper roller bearings.

The planet gears have a splined internal profile that mesh with the two joints connected to the two driveshafts that transmit the drive to the wheels.

1. Differential gear casing

2. Ring gear

3. Planet gear

4. Planet gear

5. Satellite gear

6. Satellite gear

7. Satellite carrier retaining pin

8. Satellite carrier pin

9. Ring gear retaining bolt