Transmission Fundamentals "A - Main Box"

Question 1

What are the 3 functions of a transmission?

Answer 1

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

Question 2

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

Answer 2

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

Question 3

Output torque =

Answer 3

Input torque x Final gear ratio

Question 4

Output speed =

Answer 4

Input speed / Gear ratio

Question 5

Tag nomenclature

Answer 5

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

Question 6

Trans input shaft and gear

Answer 6

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

Question 7

How are countershaft gears usually held in place?

Answer 7

Splines, a long key or individual keys

Question 8

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

Answer 8

In Mesh (constant mesh)

Question 9

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

Answer 9

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

Question 10

The mainshaft and mainshaft gears operate _________ of each other

Answer 10

Independently

Question 11

Synchromesh mainshaft gears

Answer 11

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

Question 12

What are the 3 types of synchronizers?

Answer 12

Block type
Pin type
Plate and disc

Question 13

What are the 3 stages of synchronization?

Answer 13

Energization
Synchronization
Engagement

Question 14

Basic function of a synchro

Answer 14

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.

Question 15

Synchro hub

Answer 15

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

Question 16

Synchro shift collar

Answer 16

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

Question 17

Block type synchro

Answer 17

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.

Question 18

PIn type synchro

Answer 18

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

Question 19

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

Answer 19

Dog teeth

Question 20

Plate and disc synchro

Answer 20

Similar to a clutch pack in a automatic trans.

Question 21

What is the function of the shift lever?

Answer 21

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

Question 22

Shift lever isolator

Answer 22

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

Question 23

Shift rails and forks

Answer 23

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

Question 24

Shift bar housing holds:

Answer 24

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

Question 25

What are the 3 main functions of the detents?

Answer 25

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

Question 26

Twin countershaft torque

Answer 26

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

Question 27

What is main advantage of a multiple countershaft trans?

Answer 27

Allows for the same torque capacity from a more compact unit

Question 28

Floating design mainshaft

Answer 28

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

Question 29

multiple countershaft smaller gears

Answer 29

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

Question 30

The main section of a multiple countershaft trans is generally...

Answer 30

A non-synchro, constant mesh, sliding clutch design

Question 31

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

Answer 31

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

Question 32

What are trans housing's commonly made from?

Answer 32

Eaton - Cast iron | Mack - Forged aluminum

Question 33

Input shaft bearings and seal

Answer 33

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

Question 34

What is the difference between the upper and lower countershafts?

Answer 34

The PTO gear 47 teeth on lower 45 teeth on upper

Question 35

The reverse idler runs on what?

Answer 35

Roller bearing between the gear and the shaft

Question 36

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

Answer 36

1 for each countershaft

Question 37

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

Answer 37

The gears are offset

Question 38

4 speed AUX gear positions

Answer 38

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

Question 39

What are 2 functions of a synchro assembly?

Answer 39

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

Question 40

What are 3 advantages of a multiple countershaft trans?

Answer 40

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

Question 41

The Input shaft and gear are driven by?

Answer 41

The clutch discs

Question 42

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

Answer 42

A set of double washers

Question 43

What is the function of the spring loaded plunger?

Answer 43

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