Test your Knowledge (Select the Correct Response)
1.
A hydraulic type of clutch release mechanism is normally found on heavy
construction equipment for which of the following reasons?
A.
Low-release pressure is required to operate the clutch.
B.
A slow-release action is required to operate the clutch.
C.
Extreme pressure is required to operate the clutch.
D.
Extreme release action is required to operate the clutch.
2.1.1 AUTOMATIC TRANSMISSIONS
Automatic transmissions (
Figure 7-7
) are found in all types of automotive and
construction equipment. The purpose of the automatic transmission is the same as
standard transmissions-to match the load requirements of a vehicle to the power and
speed of the engine. Changing the gear ratio automatically is controlled by throttle
position, shift control lever position, and vehicle speed. It relieves the operator of the
responsibility of selecting the best possible gear ratio for each condition and makes
driving easier and safer.
Figure 7-7 - Automatic transmission.
Many different models of automatic transmissions are manufactured today. Automotive
applications usually have three speeds forward and one reverse. More recently the
automotive industry has added a lockup clutch to the torque converter, and on some
models, an overdrive gear. Automatic transmissions for material handling and
construction equipment will normally have a lower gear ratio, be considerably larger,
and may have over six speeds forward and more than one reverse gear.
Whatever the case and regardless of design or construction, all automatic transmissions
have the following six basic systems that enable them to function:
1. A torque converter or fluid coupling
2. A hydraulic system
3. A planetary gearset (usually more than one)
NAVEDTRA 14050A
7-8