303D: Powershift & Automatic Trans Control & Shifting

Question 1

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

Answer 1

Remove leakage oil from transmission/torque converter preventing overheating from excessive buildup of oil

303D Pg. 7

Question 2

What is the purpose of the transmission priority valve?

Answer 2

Ensures that oil pressure is available for steering clutch and brake functions before transmission functions.

303D Pg. 9

Question 3

What is commonly used to control clutch release rates?

Answer 3

An orfice

Question 4

Controlling the rate of clutch application is often called what?

Answer 4

Clutch modulation

Question 5

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

Answer 5

True

Question 6

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

Answer 6

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

Question 7

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

Answer 7

shift selector valve.

Question 8

The function of the clutch pressure regulator valve is to

Answer 8

limit the application pressure

applied to the transmission clutch pistons

Question 9

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

Answer 9

converter charging circuit.

Question 10

Maximum oil pressure within the torque converter is controlled by

Answer 10

the torque converter relief valve.

Question 11

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

Answer 11

transmission lubrication circuit.

Question 12

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

Answer 12

remove leakage oil from the transmission case.

Question 13

The term clutch modulation refers to

Answer 13

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

Question 14

Oil flow for transmission control system operation is supplied by

Answer 14

a charging pump

that is driven at engine speed.

Question 15

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

Answer 15

true

Question 16

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

Answer 16

a) machine ground speed

b) the operator’s demand for power.

Question 17

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

Answer 17

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

Question 18

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

Answer 18

governor pressure.

Question 19

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.

Answer 19

false;

Question 20

The function of the modulator circuit is to

Answer 20

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.

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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

Question 23

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

Answer 23

voltage signals to the ECU that indicate the speed and

direction desired by the operator

Question 24

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

Answer 24

a speed sensor

Question 25

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

Answer 25

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

Question 26

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

Answer 26

1)input 2)processing 3) output

Question 27

Two types of shift selector

Answer 27

1) push button

2) lever

Question 28

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

Answer 28

shift solenoids.

Question 29

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

Answer 29

Speed , direction and torque converter lock-up clutch

Question 30

Energizing the solenoid shifts the valve spool to what position?

Answer 30

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

Question 31

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

Answer 31

The ECU

Question 32

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

Answer 32

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

Question 33

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

Answer 33

Clutch application circuit

Converter charging circuit

Transmission lubrication circuit

Question 34

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

Answer 34

To provide effective up shifts and downshifts

Question 35

The governor is a device that does what?

Answer 35

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

Question 36

Increasing output shaft speed will result in what?

Answer 36

Higher governor pressure before balance is achieved

Question 37

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

Answer 37

Applying and releasing clutches at the appropriate vehicle speed

Question 38

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

Answer 38

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

Question 39

Give the basic and advanced voltage range for a potentiometer

Answer 39

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

Question 40

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

Answer 40

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

Question 41

What is a common sensor to measure oil temperature?

Answer 41

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

Question 42

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

Answer 42

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

Question 43

What’s the purpose of output components?

Answer 43

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

Question 44

What typically drives the transmission charging pump?

Answer 44

An engine accessory drive or torque converter impeller.

Question 45

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

Answer 45

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

Question 46

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

Answer 46

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

Question 47

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

Answer 47

True.

Question 48

Transmission clutches are made up of?

Answer 48

Steel discs
Friction discs
Piston
Return springs

Question 49

What limits working pressure in the torque converter?

Answer 49

T/Q outlet relief valve

Question 50

Oil from the transmission oil cooler is sent where?

Answer 50

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