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Lotus Eleven/Elise/Exige. Manual - part 53

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Lotus Service Notes

Section FJ

C64 Gear Clusters (other variants similar)

The input shaft includes integral drive pinions for 1st, 2nd and reverse gears, and carries the clutch driven

plate, the 3rd/4th synchroniser and the 5th/6th synchroniser. The output shaft features an integral final drive

gear, spline fixed 3rd/4th/5th/6th driven pinions, and carries the 1st/2nd gear synchroniser. All forward gears

are constant mesh with inertia lock type synchromesh, with reverse gear attained by sliding a spur idler pinion

into engagement with both a gear on the periphery of the 1st/2nd synchroniser and a drive gear integral with

the input shaft. All gears, with the exception of reverse, use a helical tooth form for quiet running.

Sychromesh: For each gear ratio, one of the shafts has a fixed gear, and meshes with a freely revolving pinion

on the other shaft. To engage a particular gear, the freely revolving pinion must be connected to its shaft via the

sychroniser hub. This connection is made by sliding a sleeve splined to the outside of the synchroniser hub,

to engage the sleeve's internal teeth with a ring of external teeth integral with the adjacent drive pinion.

As an example, third gear selection operates as follows: Under normal road driving, when the clutch is

depressed as a precurser to a gear change, the input shaft with the third gear synchroniser are de-coupled from

the engine, but will continue to turn under decaying inertia, clutch windage, and oil drag from the drive pinions

(which are being driven from the roadwheels via the output shaft). Before the outer sleeve of the synchroniser

may be slid on its axial splines to engage with the spline ring integral with 3rd drive gear, the speeds of the two

parts must be commonised. For this purpose, a baulk (or synchroniser) ring is fitted between the two parts,

being rotationally driven by the synchroniser hub, and equipped with a female conical surface to mate with a

male cone integral with the gear. Teeth on the outside of the baulk ring, over which the synchro sleeve must

slide before engaging the third gear splines, perform a baulking function described below:

When the gear lever is operated, the outer sleeve of the synchroniser is moved towards third gear, and

pushes three spring detent plates which press the baulk ring onto the gear cone. As the input shaft train is

turning faster than third gear, the baulk ring is dragged to one end of its rotational constraint slots in the syn-

chroniser hub, in which position the internal spline teeth of the synchroniser sleeve are mis-aligned with the

teeth on the baulk ring. When further pressure is applied via the gearlever, the detent plates are overidden, and

the synchroniser sleeve splines are pressed against the ends of the baulk ring teeth, increasing the pressure

on the conical surfaces. The bevelled ends of the sleeve splines and baulk ring teeth tend to turn the ring into

alignment, but whilst a speed differential between the ring and the gear remains, the cone drag force (caused

6th gear 5th gear 4th gear 3rd gear

2nd gear 1st gear

Reverse Input shaft

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Output shaft Double cone 2nd Final drive gear

gear synchromesh

Lotus Service Notes

Section FJ

Page 6

by gear inertia) is dominant and maintains spline mis-alignment. This is the 'baulk' function.

When the speed of the input train becomes synchronised to that of third gear, there ceases to be a force

dragging the baulk ring to the end of its slots, so that the force at the bevelled ends of the splines is now domi-

nant, allowing the baulk ring to move back in its slots to align the splines and for the synchroniser sleeve to be

slid over the ring teeth towards the spline teeth on third gear. These spline teeth, whose position in relation to

those on the baulk ring is entirely random when speed synchronisation occurs, are unlikely to align, but once

the synchroniser sleeve has slid over the baulk ring teeth, there is no longer any pressure applied to the cones,

so the bevelled ends of the teeth may now complete the alignment process. Gear engagement occurs when

the sleeve completes its mating with the gear spline teeth.

On 6-speed C64 transmissions, in order to cater for the heavy demands made on the second gear syn-

chroniser, and provide high durability, this gear is fitted with a double cone mechanism to increase the conical

surface area within a small space. This process is carried further on the EC60 transmission to provide triple

cone synchromesh for 1st and 2nd speeds.

The selector mechanism cross shaft uses Teflon bushes to minimise friction, and a mass damper to improve

gearchange feel. An interlock mechanism allows the selector finger to operate only one selector shaft at a time.

In order to inhibit the unintended selection of reverse gear, a spring detent mechanism is arranged to act on the

cross-shaft, in conjunction with, on 6-speed versions, a lift collar below the gear lever knob, and on 5-speeders,

a mechanism allowing selection of reverse gear only on approach from the central neutral position.

Differential

Standard cars use a conventional 'open' two bevel gear differential contained in a carrier to which is bolted

the final drive output gear, and which is supported in two taper roller bearings. Optional on some C64 equipped

models, in conjunction with electronic Lotus Traction Control (LTC), is a Torsen type limited slip differential (LSD)

in an otherwise unchanged transmission housing (Character 3 of 7 digit code on bar code label: 'O' = open; 'L'

= LSD). The LSD uses worm wheels to interconnect the two output shafts and uses the poor torque reversal

efficiency of this type of gearing to ensure that both wheels are always supplied with driving torque.

Driveshafts

On C64 models, an output extension shaft supported in a ball bearing mounted on the cylinder block, is

used on the right hand side to allow equal length drive shafts to be used. The driveshafts use Rzeppa type

joints on their outboard ends and plunging joints at the inboard ends to accommodate the driveshaft length

variation concomitant with suspension travel.

FJ.2 - GEARCHANGE MECHANISM

6-Speed

The gear lever is spring biased towards

the 3rd/4th gear plane, and must be moved

against light spring pressure to the left before

selecting first or second gear, or against similar

pressure to the right before selecting 5th or

6th speed.

Engaging Reverse Gear:

With the vehicle at a

complete standstill, pause for a moment with the clutch pedal fully depressed be-

fore moving the lever to the left, raising the lift collar beneath the knob, and then further to the left over a spring

detent before finally pushing forwards to engage the gear.

LIFT

COLLAR

6-SPEED CHANGE PATTERN

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Lotus Service Notes

Section FJ

Crossgate Gearchange Cable Schematic (prior May '07)

Shift

Reverse gate lift collar

Reverse

gate Crossgate Crossgate cable

release bellcrank lever

cable Shift cable

Gear lever

ball pivot Reverse gate Abutment

stop arm block

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5-Speed

The gear lever is spring biased towards

the 3rd/4th gear plane, and must be moved

against light spring pressure to the left before

selecting first or second gear, or against similar

pressure to the right before selecting 5th.

Engaging Reverse Gear:

With the vehicle at a

complete stand-

still, pause for a moment with the clutch

pedal fully depressed before moving the lever

against spring pressure fully to the right, and

then rearwards to engage the gear. Note that

an inhibit mechanism requires that the lever

approaches reverse gear only from the central

neutral position. Direct access from 5th gear

is blocked.

A two cable mechanism is used to connect the gearchange lever with the transmission, one cable ('shift')

to transmit the fore/aft movement of the lever, and a second ('crossgate') cable for the sideways movement.

The gearchange lever is pivotted at its base and operates the shift cable directly via a ball joint half way up the

lever. The base of the lever has an extended ball pin on the right hand side which engages with a crossgate

bellcrank lever, the other leg of which operates the crossgate cable. An inhibit mechanism prevents the gear

lever being moved into the reverse gear plane unless a collar beneath the gear knob is lifted. Prior to May '07,

the collar is connected by control cable to a pivotted stop arm sprung to an 'up' position. In this position, a stop

pin on the crossgate bellcrank lever abuts against the end of the stop arm and prevents gearlever movement

into the reverse gear plane. When the collar is lifted, the stop arm is pulled down against its spring, to clear the

stop pin and allow reverse gate selection. From May '07 on 6-speed cars , lifting the collar raises a boss at the

base of the lever above a curved inhibitor block, allowing the lever full leftward movement.

5-SPEED CHANGE PATTERN

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Lotus Service Notes

Section FJ

Page 8

The front end of both inner cables are equipped with socket joints which may be clipped on and off the ball

pins provided on the gearchange mechanism. The outer cables are retained by a forked plastic block bolted

into the gearlever/handbrake mounting frame.

The gear cables are routed along the centre of the cabin floor, beneath the fuel tank bay, and loop under

the engine to an abutment bracket on the top of the transmission housing. Both cables are retained in the

abutment bracket by spring 'C' clips. The shift cable is fitted on the left, and uses a bellcrank lever and ball

jointed link to connect with the transmission cross-shaft lever, in order to rotate the shaft. The cross-shaft lever

incorporates an inertia weight to smooth the gearchange action and improve feel. The crossgate cable is fitted

on the right and uses a centre pivotted lever arm to impart an axial motion to the transmission cross-shaft. The

ends of both inner cables threaded into alloy eyes which are retained on the lever pins by 'R' clips.

Gearchange Cable Adjustment

Prior May '07:

Under normal circumstances, no adjustment to the gear cables should be required. If a cable is replaced

in service, it may be necessary to make minor adjustments via the threaded ball joint at the front of the cable

in order to accommodate lever movement within the shroud aperture.

From May '07: 6-speed:

In order to ensure smooth selection of 1st/2nd gears, it is important to set the crossgate cable adjustment in

relation to the reverse inhibitor block.

Push the lever to the left to abut against the reverse inhibitor block, and check selection of 1st and 2nd

gears. There should be no obstruction to fore/aft movement of the lever.

If fore/aft baulking occurs, remove the gear lever shroud. Release the ball pin from the crossgate bellcrank

lever, release the locknut and screw the ball joint socket one turn up or down the cable end before re-

attaching to the bellcrank and testing. Once a setting is found which allows smooth fore/aft lever movement

whilst abuting against the inhibitor block, secure the ball joint socket with the locknut.

Raise the reverse inhibit gear lever collar and check that reverse gear can be engaged.

Refit the shroud and check that all gears can be selected without the lever fouling the shroud aperture. If

necessary, fit shim washers behind the reverse inhibitor block to move the lever away from the LH side of

C56/C64 Transmission 'R' clip 'C' clip

External Levers

Shift bellcrank lever

Crossgate cable

Crossgate

Inertia lever Shift cable

weight

Transmission

cross-shaft

housing

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