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Drivetrains Test > 15 Speed Power Shift Transmission > Flashcards

15 Speed Power Shift Transmission Flashcards

1
Q

What is the focus of the material regarding the 55 Series John Deere?

A

The material deals with the 15 speed powershift transmission found on a 55 series John Deere tractor.

50 & 60 series transmissions are virtually the same.

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2
Q

How is the control system of the 15 speed transmission operated?

A

The control system is manually operated, similar to the 8 speed transmission.

All shift valves and control of oil flow is done by mechanical means.

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3
Q

What component does the system incorporate to control oil flow?

A

The system incorporates a rotary shift valve which provides and controls pilot oil to and from a variety of shift valves.

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4
Q

What components are responsible for metering oil flow in the transmission?

A

A number of modulating & metering valves along with several accumulators are responsible for metering oil flow to the various clutch & brake packs.

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5
Q

What is the purpose of metering oil flow in the transmission?

A

The purpose is to provide satisfactory shifting during operation.

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6
Q

What will be studied in the material regarding the control systems?

A

Only a portion of the system will be studied to show some of the differences and similarities between the two control systems.

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7
Q

What components make up the John Deere 15 Speed PST transmission?

A

The transmission consists of two traction clutches, a single compound input planetary, and a multiple compound output planetary.

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8
Q

How many forward and reverse speeds does the John Deere 15 Speed PST transmission provide?

A

It provides 15 forward speeds and 4 reverse speeds.

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9
Q

What determines the number of speeds in the John Deere 15 Speed PST transmission?

A

The different combinations of brakes and clutches in the planetary packs, plus the engagement of one or both traction clutches.

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10
Q

What is the main difference between the 15 Speed Powershift Transmission and the 8 speed?

A

The 15 Speed Powershift Transmission has an input planetary added between the C2 clutch and the B1 sun gear of the planetary pack.

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11
Q

What are the two additional elements in the 15 Speed Powershift Transmission?

A

The two additional elements are CLo and BHi.

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12
Q

What happens when CLo is engaged in the 15 Speed Powershift Transmission?

A

When CLo is engaged, the sun gear and carrier are locked together, producing a direct drive ratio through the input planetary.

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13
Q

What is the result of engaging BHi in the 15 Speed Powershift Transmission?

A

With BHi engaged, the sun gear is held, the carrier is the input, and the ring gear is the output, producing an overdrive ratio through the input planetary.

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14
Q

How many possible input speeds are there to the output carrier in the 15 Speed Powershift Transmission?

A

There are a total of eight possible input speeds to the output carrier.

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15
Q

What is the output planetary used in the 15 Speed Powershift Transmission?

A

The output planetary is the same as that used with an 8 speed.

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16
Q

In theory, how many forward speeds are available in the 15 Speed Powershift Transmission?

A

In theory, there are now 16 forward speeds available.

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17
Q

What are the C1 and C2 traction clutch drums bolted to?

A

The C1 (A) and C2 (B) traction clutch drums are bolted directly to the engine flywheel.

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18
Q

How are the C1 and C2 separator plates attached?

A

C1 & C2 separator plates are tanged to each clutch drum.

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19
Q

How are the clutch disks connected to their respective clutch hubs?

A

Clutch disks (C) are splined to their respective clutch hubs.

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20
Q

What is the design purpose of the hollow C2 shaft?

A

The hollow C2 shaft is specially designed to act as a torsional damper to absorb power pulses from the engine.

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21
Q

What is the function of the PTO stub shaft with drive gear?

A

The PTO stub shaft with drive gear (G) is splined to the C2 clutch drum and also drives the transmission/charge pump.

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22
Q

Can C1 or C2 be used individually or together?

A

Either C1 or C2 may be used individually as an input, or they may be used together in the higher gear selections - transport gears - 12 to 15.

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23
Q

What is the input for the B2 planetary and C2 clutch?

A

Like the 8 speed, the C1 clutch is the input for the B2 planetary and the C2 clutch is the input for the B1 planetary.

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24
Q

How is the C1 shaft connected in relation to the B2 sun?

A

C1 shaft is connected to the B2 sun.

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25
Q

How is the C2 shaft connected in relation to the B1 sun gear?

A

C2 shaft is connected to the B1 sun gear through the two speed input planetary.

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26
Q

What are the two drive combinations of the input planetary assembly?

A

The two drive combinations are direct drive and overdrive.

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27
Q

What is the input shaft of the planetary assembly?

A

The input is always the C2 shaft (B).

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28
Q

How does the C1 shaft drive to the output planetary?

A

The C1 shaft drives directly through to the output planetary → B2 sun gear.

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29
Q

What components are splined to the C2 input shaft?

A

The Clo hub (D) and planetary carrier (E) are both splined to the C2 input shaft.

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30
Q

How are Clo and Bhi actuated?

A

Clo and Bhi are both hydraulically actuated elements.

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31
Q

What is the drive ratio when the Clo clutch is applied?

A

With the Clo clutch applied, the ratio is direct drive.

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32
Q

What is the drive ratio when the Bhi brake is applied?

A

With the Bhi brake applied, the ratio is overdrive.

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33
Q

When must either Clo or Bhi be used?

A

Either Clo or Bhi must be used when the C2 clutch is engaged.

34
Q

What is the effect of the overdrive ratio?

A

The overdrive ratio provides an approx 15% speed increase.

35
Q

What has changed in the 15 Speed PST engagement chart compared to the 8 speed powershift?

A

The engagement chart has changed somewhat.

Most notably, there are now four elements engaged for each selected gear - three input & one output.

36
Q

What are the three additional input speeds produced in the 15 Speed PST?

A

The three additional input speeds are produced with the following selections: C2 BHi & B1, C2 BHi & B2, and C1 C2 & BHi - which provides an overdrive input.

37
Q

How have the ratios in the planetary pack changed in the 15 speed compared to the 8 speed?

A

The ratios in the planetary pack of a 15 speed have changed to provide the desired overall ratio through the transmission.

38
Q

Which gears apply CLo & BHi in the 15 Speed PST?

A

CLo & BHi are applied in several gears even though they are not required in gears that do not use C2.

39
Q

What happens when both C1 and C2 are shifted up?

A

Engagement oil from the clutch valve (G) flows through both valves to the B1 - B2 shift valve (A).

40
Q

What occurs with C2 up and C1 down?

A

Oil from the clutch valve flows through the C2 & C1 shift valves to engage the C1 clutch (B).

41
Q

How is engagement oil routed from the fid - rev valve?

A

Engagement oil from the fid - rev valve (C) is routed through the shifted C1 valve to supply the B1 - B2 shift valve (A).

42
Q

What happens when both C1 and C2 are shifted down?

A

Oil from the clutch valve flows through the C2 shift valve, to the C1 shift valve, where it is blocked and forced to engage the C2 clutch (E).

43
Q

What is the connection of C1 at this point?

A

C1 is connected to sump, and engagement oil from the fwd - rev valve is routed through the shifted C1 valve to supply the B1 - B2 shift valve.

44
Q

What occurs with C2 shifted down and C1 up?

A

Oil from the clutch valve is sent to engage both C1 and C2 clutches.

45
Q

What is the connection of the B1 - B2 shift valve at this point?

A

The B1 - B2 shift valve is connected to sump.

46
Q

What does ‘G’ represent in the system?

A

System Pressure

47
Q

What does ‘I’ represent in the system?

A

Sump Oil

48
Q

What happens when the modulator valve is shifted to neutral?

A

Engagement oil (A) flows through the modulator valve (B), to the fwd/rev valve (D) and to an element if shifted to a gear.

49
Q

What effect does oil flowing through the modulator valve have?

A

It acts on the left end of the modulator valve.

50
Q

Where else does oil flow from the modulator valve?

A

Oil is orificed to the spring end, the accumulator piston (C), and the top end of the sump valve (F).

51
Q

What does pressure on the top side of the sump valve (F) do?

A

It forces the valve down, opening the passage to the sump and allowing flow through the modulator orifice.

52
Q

What is the balancing effect in the modulator valve?

A

Spring pressure on the right side opposes pilot oil pressure on the left side of the valve.

53
Q

What pressure is maintained as the modulator valve shuttles?

A

A pressure of approximately 12 psi will be maintained to the forward/reverse valve.

54
Q

What happens when the lever is shifted to a gear?

A

The rotary valve (E) sends 175 psi pilot oil to the bottom of the sump valve (F), causing it to close.

55
Q

How does oil flow through the modulator valve?

A

Oil continues to flow through the orifice in the modulator valve (B) and builds pressure against the spring end of the valve.

56
Q

What controls the rate at which pressure builds in the modulator valve?

A

The resistance of the accumulator spring controls the rate at which pressure builds, and the accumulator begins to fill.

57
Q

What happens as pressure increases in the modulator valve?

A

Increasing pressure causes the modulator valve to move left, allowing increased flow to the oncoming element.

58
Q

What occurs as the element fills with pressure?

A

As the element fills, pressure in the circuit increases, allowing more pilot pressure to the left side of the modulator valve, smoothly engaging the oncoming element.

59
Q

What happens when approximately 90 psi is reached?

A

The accumulator piston will bottom out, and pressure to the element will immediately increase to 175 psi, providing full engagement.

60
Q

How long does the modulation cycle take?

A

The modulation cycle takes about 2 - 2.5 seconds.

61
Q

What happens when the gearshift lever is moved back to neutral?

A

The rotary valve routes pilot oil at the bottom end of the sump valve back to sump.

62
Q

What causes the sump valve to move down?

A

Pressure oil on the top side of the sump valve.

63
Q

What does the sump valve do after moving down?

A

Routes the oil from the accumulator and spring end of the modulator valve back to sump.

64
Q

What happens to the modulator valve when engagement pressure is applied?

A

It momentarily forces the valve to the right, dumping oil from the engagement circuit back to sump.

65
Q

What occurs after pressure is relieved in the modulator valve?

A

The modulator valve will shuttle between the centre and right envelopes, maintaining 12 psi to the forward/reverse valve.

66
Q

What is required when shuttle shifting between forward and reverse gears?

A

The gearshift lever must spend enough time in neutral for the accumulator to get totally discharged (0.5 - 1 sec).

67
Q

What is Clutch Modulation?

A

Clutch Modulation involves controlling the application time of clutches using metering valves.

68
Q

How does the metering valve work in the C3 clutch system?

A

The metering valve controls oil flow to the C3 clutch and operates similarly for the B4 clutch.

69
Q

Where is the metering valve connected?

A

The metering valve is connected in parallel to the main clutch actuating circuit for C3 and B4.

70
Q

What happens in speeds 1-11F, 1-4R, NN, NF, and NR?

A

Pilot pressure oil (B) is routed to the backside of the accumulator pistons, preventing modulation.

71
Q

What effect does the pilot pressure oil have on the accumulator pistons?

A

It forces the accumulator pistons to remain stationary, preventing modulation.

72
Q

Does engagement oil flow through the metering valves?

A

Yes, engagement oil (A or C) still flows through the orifice in the metering valves.

73
Q

What is the effect of the metering valve when accumulator pistons are stationary?

A

The metering valve has no effect since the accumulator pistons are held stationary.

74
Q

What happens when the gearshift lever is placed in 12F?

A

Pilot oil (B) between the accumulators is routed to sump.

75
Q

What is routed to the C3 clutch when engagement oil is activated?

A

Engagement oil from the C3 shift valve (A) is routed to the C3 clutch as well as the C3 metering valve.

76
Q

Why does the metering valve shift to the left?

A

Because oil is metered to the spring end of the valve, pressure is greater on the head end.

77
Q

What happens as the accumulator is charged?

A

Pressure increases on the spring end of the metering valve, causing the valve to gradually shift to the right.

78
Q

What effect does the shifting of the metering valve have on oil flow?

A

It slows down the flow of oil to sump and increases element engagement pressure.

79
Q

At what pressure does the accumulator bottom out?

A

The accumulator bottoms out at approximately 58 psi.

80
Q

What happens to engagement oil (D) when the accumulator bottoms out?

A

Engagement oil (D) immediately increases to system pressure and the element is fully engaged.

Drivetrains Test (4 decks)

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