190303d Flashcards

1
Q

What is the purpose of the transmission scavenging pump and the torque converter scavenging pump?

A

To remove leakage oil from transmission/torque converter therefore removing built up oil that has become hot, preventing over heating.

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2
Q

What is the purpose of the priority valve?

A

It is to ensure that oil pressure is available for steering clutch and brake functions before transmission functions.

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3
Q

What exactly is a priority valve?

A

A normally closed pressure control valve.

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4
Q

Why is there an inlet relief valve on a transmission charge system?

A

This is for cold weather starts until the torque converter oil warms up.

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5
Q

Transmission and hydraulic oil are very similar. What is the difference?

A

Transmission oils are specifically formulated to provide maximum life of the friction material of the clutch discs.

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6
Q

What is commonly used to control clutch release rates?

A

An orfice

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7
Q

Controlling the rate of clutch application is often called what?

A

Clutch modulation

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8
Q

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

A

True

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9
Q

The three (3) hydraulic circuits in a basic shift control system are:

A

a) the clutch application circuit
b) the converter charging circuit
c) the transmission lubrication circuit

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10
Q

In a basic hydraulic shift control system, transmission speed and direction changes
are made by the:

A

shift selector valve.

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11
Q

The function of the clutch pressure regulator valve is to

A

limit the application pressure

applied to the transmission clutch pistons

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12
Q

The circuit that receives oil flow after the clutch application circuit has been satisfied,
is the:

A

converter charging circuit.

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13
Q

Maximum oil pressure within the torque converter is controlled by

A

the torque converter relief valve.

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14
Q

Torque converter outlet oil flow is cooled and filtered before it is directed into the

A

transmission lubrication circuit.

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15
Q

Some transmissions are equipped with a scavenging pump whose function is to:

A

remove leakage oil from the transmission case.

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16
Q

The term clutch modulation refers to

A

controlling the buildup of pressure in the clutch piston allowing controlled slippage of the clutch discs.

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17
Q

Oil flow for transmission control system operation is supplied by

A

a charging pump

that is driven at engine speed.

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18
Q

The purpose of modulating the application of transmission clutches is to prevent shift shock.

A

true

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19
Q
The two (2) factors that influence the point at which an automatic transmission will
shift are:
A

a) machine ground speed

b) the operator’s demand for power.

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20
Q

The function of the governor circuit in and automatic transmission is to:

A

provide a hydraulic signal that is proportional to machine ground speed.

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21
Q

The hydraulic governor in an automatic transmission operates by balancing the
centrifugal force of the governor flyweights against:

A

governor pressure.

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22
Q

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.

A

false;

23
Q

The function of the modulator circuit is to

A

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.

24
Q

If a clutch releases much more quickly than the next clutch is applied during a shift,
the result is

A

a flare up of engine rpm and a momentary freewheeling of the machine
until the next clutch is fully applied.

25
Q

Momentary engine lugging and slowing of machine speed during shifting indicates
that

A

this condition is a result of a releasing clutch that does not fully release before
the next clutch is applied.

26
Q

The shift selector of an electronically shifted automatic transmission consists of a
number of switches that sends __ signals to the ECU that indicate .

A

voltage signals to the ECU that indicate the speed and

direction desired by the operator

27
Q
What component of an electronic automatic shift control system performs the same
function as the governor in hydraulically controlled systems?
A

a speed sensor

28
Q

List four (4) functions of the ECU in an electronically controlled shift system.

A

a) control upshifts and downshifts
b) control clutch modulation
c) provide diagnostic information
d) provide a warning to the operator when a malfunction occurs

29
Q

Electronic transmission shift control system can be group into what three groups

A

1)input 2)processing 3) output

30
Q

Two types of shift selector

A

1) push button

2) lever

31
Q

The output devices that are responsible for causing speed and direction changes are

A

shift solenoids.

32
Q

Solenoids are the output components that are responsible for what on the transmission?

A

Speed , direction and torque converter lock-up clutch

33
Q

Energizing the solenoid shifts the valve spool to what position?

A

Spool moves to closed position blocking sump port so clutch application can occur

34
Q

Wiring harness and connectors are used to connect each individual component to?

A

The ECU

35
Q

The shift controls of an automatic transmission provide more efficient machine operation than the shift control on a power shift transmission because?

A

The transmission automatically shifts speed ranges at the optimum time in the machines operating cycle

36
Q

Automatic transmissions have the same three basic circuits as a powershift transmission… what are they?

A

Clutch application circuit

Converter charging circuit

Transmission lubrication circuit

37
Q

Why must the control system be able to reference machine ground speed? (Automatic transmission)

A

To provide effective up shifts and downshifts

38
Q

The governor is a device that does what?

A

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

39
Q

Increasing output shaft speed will result in what?

A

Higher governor pressure before balance is achieved

40
Q

Governor pressure acting on the valves within the transmission valve body are responsible for what?

A

Applying and releasing clutches at the appropriate vehicle speed

41
Q

The throttle position sensor (TPS) indicates the operators demand for what?

A

For power. The information provided goes through the electronic management system which is connected to the throttle.

42
Q

Give the basic and advanced voltage range for a potentiometer

A

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

43
Q

Where are pressure switches installed in the transmission ( what circuit) ?

A

In the hydraulic circuit of the transmission, to inform the ECU what circuits are pressurized and if pressure measured is within spec

44
Q

What is a common sensor to measure oil temperature?

A

It’s commonly sensed by a thermistor( first year review)

45
Q

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

A

It allows two way communication. Not only sending information but receiving it.

46
Q

What’s the purpose of output components?

A

They respond to the electrical signal sent to them by the ECU and create an output action or provide information regarding transmission performance.

47
Q

What typically drives the transmission charging pump?

A

An engine accessory drive or torque converter impeller.

48
Q

What is the shift system in a powershift or automatic transmission responsible for?

A

Applying the appropriate transmission clutches so that the machine operates in the proper gear for efficient machine operation.

49
Q

What two inputs must an automatic transmission monitor to make effective shifts?

A

Machine ground speed and the operator’s demand for engine power.

50
Q

All powershift and automatic transmission gearing components are pressure lubricated. (T/F)

A

True.

51
Q

Transmission clutches are made up of?

A

Steel discs
Friction discs
Piston
Return springs

52
Q

What limits working pressure in the torque converter?

A

T/Q outlet relief valve

53
Q

Oil from the transmission oil cooler is sent where?

A

Back to the transmission to be used for cooling and lubricating transmission components