198002766 - INTRODUCTON - MANUAL GEARBOX WITH DIFFERENTIAL
SPECIFICATIONS
Transverse five/six speed gearbox with two shafts supported by roller bearings and additional shaft for reverse with double idler gears and synchromesh.The external controls have a twin cable.The structure of the gearbox consists of:- a "closed end" gearbox casing configuration, the rear cover having been eliminated. This contains and supports the main and lay shafts, the gear engagement forks and rods and the gear selector/engagement device;- clutch bell housing which contains the clutch and associated coaxial control device (CSC).Gears are splash lubricated and also lubricated by means of ducts inside the following components:- clutch casing and gearbox casing;- 3rd and 4th speed control rod;- main shaft.The excellent lubrication of the ducts makes it possible to:- improve the efficiency of the lubrication;- reduce the amount of oil used thanks to the lubrication aimed at the main couplings.
The main shaft is supported by two high precision taper bearings.The main shaft rear bearing (1) has a Viton ring device (2), which compensates for axial thermal expansion of the gearbox casing and the main shaft.This ring makes it possible to:- reduce synchroniser wear;- improve the matching of the gears;- reduce noise from the bearings;- improve the manoeuvrability of the gearbox.
The main shaft consists of:- 1st speed, reverse and 2nd speed gears formed out of one piece;- gears for 3rd, 4th and 5th/6th speeds, fitted on needle bearings with synchronisers.
Layshaft
The layshaft consists of:- gears for 1st and 2nd speeds, fitted on needle bearings with synchronisers;- 3rd, 4th and 5th/6th speed gears fitted on the shaft.The layshaft is supported by two high precision taper bearings.
Gears
All the gears are designed with high contact factor teeth, i.e. when one of the teeth in the coupling is in contact, the next one has already begun meshing. This has the advantage of:- reducing transmission irregularities;- reducing operating noise.The gears for 2nd and 5th/6th speeds and the final drive gears have undergone a "super-finish" treatment on the teeth after the thermal treatment.The gears are the following type:- helical toothed for the forward gears;- straight toothed for reverse gear.
Synchronisers
The synchronisers for all the gears are Borg Warner, with the following brass baulk rings:- triple cone (1) for 1st and 2nd speeds;- single cone (2) for the 3rd, 4th and 5th/6th speeds.Multiple cone synchronisers make it possible to:- distribute the lever engagement load over several cones;- facilitate the engagement of the gears.
GEAR ENGAGEMENT/SELECTION SYSTEM
The gear engagement/selection system has four selection planes with the gear positioner fitted with a bearing.The system ensures that it is impossible to engage reverse gear accidentally because it is on a separate plane.Bushes with a Permaglide (6) facing are used to reduce wear on:- the couplings between the gear engagement/selector control shaft and the gearbox casing;- the couplings between the fork rods and the gearbox casing.The bushes make it possible to:- achieve improved sliding;- produce more accurate gear engagement.
