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Transmissions > Transmission Fundamentals "A - Main Box" > Flashcards

Transmission Fundamentals "A - Main Box" Flashcards

1
Q

What are the 3 functions of a transmission?

A

Multiply torque from engine
Provide a means of reversing torque
Provide an interruption in flow of torque (neutral)

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2
Q

What are the common ways of classifying a transmission? (5)

A 
Synchronized or non
# of countershafts
Number of forward gears
Final gear ratio (direct or overdrive)
Shifting method
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3
Q

Output torque =

A

Input torque x Final gear ratio

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4
Q

Output speed =

A

Input speed / Gear ratio

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5
Q

Tag nomenclature

A

R= roadranger, T= twin countershaft, L= low inertia, O= overdrive
First 2 numbers= torque x 100, Number 4-5= speeds

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6
Q

Trans input shaft and gear

A

Sometimes called clutch shaft. Gear can also be called the trans drive gear or main gear

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7
Q

How are countershaft gears usually held in place?

A

Splines, a long key or individual keys

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8
Q

The main shaft and countershaft are said to be in what all the time?

A

In Mesh (constant mesh)

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9
Q

What is commonly used to control axial endplay in a trans with helical cut gears?

A

Opposed taper roller bearings, as well as a series of snap rings and thrust washers

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10
Q

The mainshaft and mainshaft gears operate _________ of each other

A

Independently

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11
Q

Synchromesh mainshaft gears

A

Rotate on a needle bearing and a thin film of lubrication. Commonly helical design using snap rings and thrust washers to control end thrust.

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12
Q

What are the 3 types of synchronizers?

A

Block type
Pin type
Plate and disc

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13
Q

What are the 3 stages of synchronization?

A

Energization
Synchronization
Engagement

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14
Q

Basic function of a synchro

A

Can think of as a clutch or brake that is used to match or synchronize the speed of the main shaft with the speed of the mainshaft during shifting.

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15
Q

Synchro hub

A

Is the piece that slides directly over the main shaft splines.

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16
Q

Synchro shift collar

A

Is mated with shift fork, becomes the piece that carriers torque from the main gear to the synchro hub

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17
Q

Block type synchro

A

The fork moves the shift collar carrying inserts toward gear to be selected. the inserts push against the blocker ring. The friction of blocker ring against gear slows gear until speed matches. Once the speeds match the collar slides onto gear and tension against the blocker ring is released.

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18
Q

PIn type synchro

A

Synchro cups are splined to the main gears at all times. The blocker rings and the shift collar are one assembly.

19
Q

What do the teeth on a synchro engage with on main shaft gear?

A

Dog teeth

20
Q

Plate and disc synchro

A

Similar to a clutch pack in a automatic trans.

21
Q

What is the function of the shift lever?

A

To transmit the actions of the operator to the shift forks and rails

22
Q

Shift lever isolator

A

Connects the upper level to the lower lever. Used to reduce the amount of noise transmitted into cab

23
Q

Shift rails and forks

A

The shift lever moves the shift blocks that are attached to the rails. Attached to the rails are the shift forks that move the sliding clutch on the mainshaft

24
Q

Shift bar housing holds:

A 
Detents
Interlock components
Air valve shaft/ pre select valve
Reverse light switch
Neutral indicator switch
25
Q

What are the 3 main functions of the detents?

A

Hold shift rail in selected position
Provide shift feel
Help control max travel

26
Q

Twin countershaft torque

A

Is split evenly between the 2 countershafts which are positioned 180 deg apart

27
Q

What is main advantage of a multiple countershaft trans?

A

Allows for the same torque capacity from a more compact unit

28
Q

Floating design mainshaft

A

Because the main shaft assm is positioned directly between each countershaft shafts the forces trying to move the main shaft are equal and offsetting.

29
Q

multiple countershaft smaller gears

A

Because of the doubled tooth contact area the gears can be narrower. As well a less expensive spur cut gear can be used which eliminates the need for thrust control washers. Makes for a shorter, more compact unit

30
Q

The main section of a multiple countershaft trans is generally…

A

A non-synchro, constant mesh, sliding clutch design

31
Q

How is torque transferred from the countershaft to the main shaft?

A

Countershaft gear, to the main gear, to the sliding clutch, to the main shaft

32
Q

What are trans housing’s commonly made from?

A

Eaton - Cast iron

Mack - Forged aluminum

33
Q

Input shaft bearings and seal

A

Uses a wind back seal
Supported at front by pilot bearing
Supported at back by input shaft bearing
Has a bushing in rear of shaft to support the front of the main shaft

34
Q

What is the difference between the upper and lower countershafts?

A

The PTO gear
47 teeth on lower
45 teeth on upper

35
Q

The reverse idler runs on what?

A

Roller bearing between the gear and the shaft

36
Q

How many P.O.P’s are there in a multiple countershaft trans.?

A

1 for each countershaft

37
Q

When looking at diagram how can you tell which gear is reverse?

A

The gears are offset

38
Q

4 speed AUX gear positions

A

The speed is the gear closest to the middle. H-H is direct drive, both collars are in mesh with centre gear

39
Q

What are 2 functions of a synchro assembly?

A

Match the speed of mainshaft gear with speed of mainshaft
To temporarily connect a selected mainshaft gear to the mainshaft once the speeds of the mating parts have been synchronized

40
Q

What are 3 advantages of a multiple countershaft trans?

A

Countershafts, bearings and housings can be lighter
Floating design eliminates need for bearings between the mainshaft and gears
Gear width can be half as wide, as well as spur cuts gears and no thrust washers

41
Q

The Input shaft and gear are driven by?

A

The clutch discs

42
Q

The mainshaft gears are located in place on the mainshaft by?

A

A set of double washers

43
Q

What is the function of the spring loaded plunger?

A

Prevents the operator from selecting first or reverse when the vehicle is moving forward at a great speed

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