Future Transmissions
Transmission technology is always advancing, and
some entirely new concepts are being developed. The fol-
lowing section discusses transmissions that may appear in
future vehicles.
Toroidal or Infinitely Variable
Transmission (IVT)
Figure 1-41 shows an infinitely variable transmission
(IVT), also known as a toroidal transmission, that is cur-
rently being used in Asia. This type of transmission may
eventually be installed in vehicles made for American and
European roads. The IVT consists of a set of movable discs
that rotate between drive and driven races. Varying the
angle of the discs varies the speed ratio between the drive
and driven races. Since sending power through the discs
reverses the direction of rotation, a second set of movable
discs are installed behind the driven race. The driven race
powers a final output race through the discs. This again
reverses power flow so that power exits the transmission in
the same direction as it entered. The combination of ratios
between the two sets of discs results in the final transmis-
sion ratio.
The angles of the movable discs are varied by servos
that are operated by the transmission’s hydraulic system.
An onboard computer monitors and adjusts the hydraulic
system outputs based on inputs from engine and road
speed sensors.
Chapter 1 Introduction to Automatic Transmissions and Transaxles 31
Automatic
transmission
Line
fittings
Line
clamp
Oil cooler
inside radiator
Upper oil cooler
feed line
Lower oil cooler
return line
Radiator
Figure 1-38. To cool the transmission fluid, an oil cooler is often installed in the vehicle’s radiator. Transmission oil pressure forces
fluid through the cooler, where it gives up heat to the engine coolant. The cooled fluid then returns to the transmission. Hot fluid
usually comes directly from the torque converter, where most transmission heat is generated. (General Motors)
Transmission
housing
Transmission
filter
Oil pan
Figure 1-39. The transmission filter is located at the lowest
point in the transmission, usually in the lower oil pan. This
allows it to pick up transmission fluid, even when the fluid level
is slightly low. (General Motors)
Note: The motor-generator in some mild
hybrids can move the vehicle if the engine
fails.This allows a vehicle with an inoperable
engine to be driven to a service facility.