190303d Flashcards
What is the purpose of the transmission scavenging pump and the torque converter scavenging pump?
To remove leakage oil from transmission/torque converter therefore removing built up oil that has become hot, preventing over heating.
What is the purpose of the priority valve?
It is to ensure that oil pressure is available for steering clutch and brake functions before transmission functions.
What exactly is a priority valve?
A normally closed pressure control valve.
Why is there an inlet relief valve on a transmission charge system?
This is for cold weather starts until the torque converter oil warms up.
Transmission and hydraulic oil are very similar. What is the difference?
Transmission oils are specifically formulated to provide maximum life of the friction material of the clutch discs.
What is commonly used to control clutch release rates?
An orfice
Controlling the rate of clutch application is often called what?
Clutch modulation
A desirable feature in most heavy equipment applications is the ability to prevent automatic shifting from occurring during certain phases of the machine’s operating cycle.
T/F
True
The three (3) hydraulic circuits in a basic shift control system are:
a) the clutch application circuit
b) the converter charging circuit
c) the transmission lubrication circuit
In a basic hydraulic shift control system, transmission speed and direction changes
are made by the:
shift selector valve.
The function of the clutch pressure regulator valve is to
limit the application pressure
applied to the transmission clutch pistons
The circuit that receives oil flow after the clutch application circuit has been satisfied,
is the:
converter charging circuit.
Maximum oil pressure within the torque converter is controlled by
the torque converter relief valve.
Torque converter outlet oil flow is cooled and filtered before it is directed into the
transmission lubrication circuit.
Some transmissions are equipped with a scavenging pump whose function is to:
remove leakage oil from the transmission case.
The term clutch modulation refers to
controlling the buildup of pressure in the clutch piston allowing controlled slippage of the clutch discs.
Oil flow for transmission control system operation is supplied by
a charging pump
that is driven at engine speed.
The purpose of modulating the application of transmission clutches is to prevent shift shock.
true
The two (2) factors that influence the point at which an automatic transmission will shift are:
a) machine ground speed
b) the operator’s demand for power.
The function of the governor circuit in and automatic transmission is to:
provide a hydraulic signal that is proportional to machine ground speed.
The hydraulic governor in an automatic transmission operates by balancing the
centrifugal force of the governor flyweights against:
governor pressure.
Some automatic transmissions allow the adjustment of automatic shift points. This is
normally accomplished by replacing the shift signal valves with ones of differing areas.
false;
The function of the modulator circuit is to
provide a hydraulic signal pressure that is
proportional to the position of the engine throttle. This pressure is used to delay
transmission shift points during wide open throttle operation.
If a clutch releases much more quickly than the next clutch is applied during a shift,
the result is
a flare up of engine rpm and a momentary freewheeling of the machine
until the next clutch is fully applied.
Momentary engine lugging and slowing of machine speed during shifting indicates
that
this condition is a result of a releasing clutch that does not fully release before
the next clutch is applied.
The shift selector of an electronically shifted automatic transmission consists of a
number of switches that sends __ signals to the ECU that indicate .
voltage signals to the ECU that indicate the speed and
direction desired by the operator
What component of an electronic automatic shift control system performs the same function as the governor in hydraulically controlled systems?
a speed sensor
List four (4) functions of the ECU in an electronically controlled shift system.
a) control upshifts and downshifts
b) control clutch modulation
c) provide diagnostic information
d) provide a warning to the operator when a malfunction occurs
Electronic transmission shift control system can be group into what three groups
1)input 2)processing 3) output
Two types of shift selector
1) push button
2) lever
The output devices that are responsible for causing speed and direction changes are
shift solenoids.
Solenoids are the output components that are responsible for what on the transmission?
Speed , direction and torque converter lock-up clutch
Energizing the solenoid shifts the valve spool to what position?
Spool moves to closed position blocking sump port so clutch application can occur
Wiring harness and connectors are used to connect each individual component to?
The ECU
The shift controls of an automatic transmission provide more efficient machine operation than the shift control on a power shift transmission because?
The transmission automatically shifts speed ranges at the optimum time in the machines operating cycle
Automatic transmissions have the same three basic circuits as a powershift transmission… what are they?
Clutch application circuit
Converter charging circuit
Transmission lubrication circuit
Why must the control system be able to reference machine ground speed? (Automatic transmission)
To provide effective up shifts and downshifts
The governor is a device that does what?
Converts the rotational speed of the transmission output shaft which is directly proportional to the ground speed of the machine to a hydraulic pressure signal that is used to control shift operations
Increasing output shaft speed will result in what?
Higher governor pressure before balance is achieved
Governor pressure acting on the valves within the transmission valve body are responsible for what?
Applying and releasing clutches at the appropriate vehicle speed
The throttle position sensor (TPS) indicates the operators demand for what?
For power. The information provided goes through the electronic management system which is connected to the throttle.
Give the basic and advanced voltage range for a potentiometer
0-5 volts is basic answer, but, 0.5-4.5 v is the correct working range
0 volts would indicate an open electrical circuit. 5 volts and over would indicate a short.
0-5 are faults
Where are pressure switches installed in the transmission ( what circuit) ?
In the hydraulic circuit of the transmission, to inform the ECU what circuits are pressurized and if pressure measured is within spec
What is a common sensor to measure oil temperature?
It’s commonly sensed by a thermistor( first year review)
The machine/engine communication link is a data link that allows what communication between the transmission ECU and other electronic control systems on the machine
It allows two way communication. Not only sending information but receiving it.
What’s the purpose of output components?
They respond to the electrical signal sent to them by the ECU and create an output action or provide information regarding transmission performance.
What typically drives the transmission charging pump?
An engine accessory drive or torque converter impeller.
What is the shift system in a powershift or automatic transmission responsible for?
Applying the appropriate transmission clutches so that the machine operates in the proper gear for efficient machine operation.
What two inputs must an automatic transmission monitor to make effective shifts?
Machine ground speed and the operator’s demand for engine power.
All powershift and automatic transmission gearing components are pressure lubricated. (T/F)
True.
Transmission clutches are made up of?
Steel discs
Friction discs
Piston
Return springs
What limits working pressure in the torque converter?
T/Q outlet relief valve
Oil from the transmission oil cooler is sent where?
Back to the transmission to be used for cooling and lubricating transmission components
