Description; Description - Torsen Differential - Lotus Elise S1 Service Notes

MANUAL GEARBOX
DESCRIPTION
The 5 speed constant mesh gearbox employs single
helical gears for speed transmission and final drive.
The input shaft carries the primary input gear,
reverse pinion, 2nd gear and 3rd, 4th and 5th gear
synchromesh hubs and idler gears. It is supported
by two ballraces. End float is controlled by selective
circlips and a Belleville washer. Its short input end
eliminates the need for support in the engine
crankshaft. The output shaft carries the final drive
pinion, 1st idler gear, 1st and 2nd synchromesh
hubs, 2nd speed idler gears and 3rd, 4th and 5th
gears. The shaft is supported in the differential
housing by a parallel roller bearing and depending
on application, is supported in the gearcase by
either a double ballrace or a single ballrace and
roller bearing. Pinion location is controlled by a
selective washer. The rear end of the shaft is
secured by a circlip which retains the bearings in the
gear case. Synchromesh is by spring rings and
spline extensions in the inner faces of the
synchromesh sleeves. Gear selection is via an
interlock and gearshift holder assembly which
transmits movement of the main selector shaft to the
selector forks. Later specification gearboxes employ
a reverse brake mechanism. Lubrication is by
splash. An oil gutter located on the upper side of the
gear case collects splashed oil and directs it to oil
guide plates which distribute it to the hollow input
and output shafts.
DESCRIPTION - TORSEN DIFFERENTIAL
Gearboxes fitted to certain models incorporate a
Torsen' limited slip differential. The word Torsen' is
derived from torque sensing which describes the
principle of operation.
Two types of differential are fitted, type A is fitted to
gearboxes having serial number prefixes K4BX and
K7BSUT. Type B is fitted to gearboxes having serial
number prefixes C6FTUT; W4DTUT; C6DTUT and
C6DTUTH.
mesh with the helical gears and the spur gears
mesh with those of the adjoining element gear
assembly. Axial thrust of the helical gears is
controlled by a combination of thrust washers and
needle roller bearings located at each end of and
between the two gears.
Type B
The assembly comprises a final drive gear bolted to
the differential casing two helical side gears splined
to the drive shafts and four pairs of element gear
assemblies arranged at ninety degree intervals
within the differential casing and running parallel to
the side gears. Each of the element gear assemblies
comprises two helical gears of unequal length, the
long gears are in constant mesh with the helical side
gears splined to the drive shafts and also with the
short gears of the adjoining element. Axial thrust of
the helical side gears is controlled by thrust washers
located between the end of each gear and the
differential casing and by a thrust washer and friction
washer located between the two gears.
OPERATION
With the exception of reverse all gears are in
constant mesh. Forward ratios are obtained by
locking a gear to its shaft using its individual
synchronizer hub and sleeve. Reverse gear is
obtained by engaging reverse idler gear with the
reverse gears changing the direction of rotation of
the output shaft. When a forward gear is selected
the synchronizer sleeve presses the synchromesh
female cone into contact with a corresponding male
cone in the gear chosen. This synchronizes the
speeds of the synchronizer hub and gear. The
synchronizer sleeve then engages the gear and by
means of a spring ring, teeth extensions on the
synchronizer sleeve and detents in the selector shaft
holds the selected gear in engagement. Torque is
transmitted from the input shaft through the selected
gear to the output shaft pinion and final drive gear to
the drive shafts.
Type A
The assembly comprises a final drive gear bolted to
the differential casing; two helical gears splined to
the drive shafts and three pairs of element gear
assemblies arranged at 120°intervals within the
differential casing and running at right angles to the
helical gears. Each of the element gear assemblies
comprises a worm gear and two spur gears running
on a journal pin. The worm gears are in constant
REVISED: 12/97
DESCRIPTION AND OPERATION 5