Lotus Elise S1 Service Notes page 291

MANUAL GEARBOX
T o r s e n differential - T y p e B - Serial n u m b e r
prefixes C6FTUT; W4DTUT; C 6 D T U T a n d
C6DTUTH
1. Helical side gear
2. Element gear assembly - helical gears
3. Friction washers
4. Thrust washers
Unlike a conventional limited slip differential, the
torque sensing differential does not rely on the
locking value of friction discs but by the friction
produced by the teeth of the two helical side gears
splined to the drive shafts meshing with the gears of
the element gear assemblies. On Type A
differentials, additional locking values are generated
by the thrust washers and needle roller bearings
located at each end of and between the side gears;
whilst on Type B differentials, a combination of thrust
washers and friction washers is used.
When both front wheel speeds are equal, then the
frictional loads imposed by the element gears on the
side gears are also equal. However, when the drive
resistance on a road wheel is reduced through loss
of traction then a torque imbalance is created; less
torque being required to turn the wheel with the
highest speed. This torque imbalance is sensed by
the differential and results in a lowering of the friction
imposed by the element gears on the side gear
driving that particular wheel. This causes a reduction
in wheel speed until a point is reached where
traction is restored, the torque required to turn both
wheels is equal and both wheels are rotating at the
same speed.
DESCRIPTION AND OPERATION 7