Transmission Fundamentals

Question 1

what are the three functions of a transmission

Answer 1

. to multiply torque from the engine through a series of gear options
. to provide a means of reversing the direction of torque delivery from the engine
. to provide an interruption in torque ( neutral ) while the clutch is still engaged

Question 2

transmission classifications

Answer 2

. synchronized or non-synchronized 
. single or multiple countershaft 
. number of forward  gear ratio 
. manual or automatic
. final gear ratio ( direct or overdrive )

Question 3

how do you calculate output torque on a transmission

Answer 3

input torque must be multiplied by the final gear ratio

Question 4

how do you calculate output speed on a transmission

Answer 4

input speed must be divided by the final gear ratio

Question 5

what are the main components in a heavy duty transmission

Answer 5

. Transmission input shaft and drive gear 
. Mainshaft and mainshaft gears 
. Synchronizers 
. a shift lever 
. shift rails and forks 
. detents 
. interlocks

Question 6

what is the initial component to receive power from the engine

Answer 6

transmission input shaft also called the clutch shaft

Question 7

what happens when the clutch is engaged

Answer 7

it is trapped between the flywheel and the pressure plate friction surface

Question 8

what is the purpose of the tapered roller bearing located in the casting ahead of the input shaft gear

Answer 8

to center the shaft in the front of the transmission case and provides a means of adjusting mainshaft endplay

Question 9

how is the input shaft bearing retainer cover adjusted to have the proper endplay on the bearing cup and cone

Answer 9

shims

Question 10

what is the mainshaft and gear assembly is different from the countershaft how ?

Answer 10

the main shaft is a sperate shaft that operates independently of the main shaft gears

Question 11

how are the helical gears on a mainshaft held in place

Answer 11

with thrust washers, snap rings and lock pins

Question 12

why are more thrust washers needed on a mainshaft than a countershaft

Answer 12

because the gears are not connected to the mainshaft so each individual gear requires thrust washers

Question 13

what is the tang on a thrust washer used for

Answer 13

as a locating device

Question 14

what is a synchronizer

Answer 14

a type of clutch or brake that is used to match the speed of the mainshaft with a mainshaft gear during the shifting process

Question 15

what are the three types of synchronizers

Answer 15

block type
plate and disc type
pin type

Question 16

what is used to transmit the actions of the operator to the shift fork and rails

Answer 16

the shift lever

Question 17

what is used to reduce transmission noise up into the cab in a shift lever assembly

Answer 17

an isolator

Question 18

what is the purpose if the shift rails and fork

Answer 18

to take the operators input from the gear shift lever and move the sliding clutches to engage the desired mainshaft gear

Question 19

what allows proper gear selection without clashing gears

Answer 19

by only allowing one sliding clutch to be moved at one time

Question 20

what is the purpose of the detents in a heavy duty transmission

Answer 20

to hold a shift rail in the selected position whether in a neutral or engaged position

Question 21

how many recesses are there in a shift rail

Answer 21

there are usually three recesses in each shift rail

Question 22

why must the operator overcome a definite amount of force to shift into first or reverse

Answer 22

to prevent accidental shifting during operation

Question 23

in order to prevent the operator from selecting more than one gear at a time

Answer 23

interlocks

Question 24

what are some advantages of multiple countershaft transmissions

Answer 24

. smaller and lighter countershafts, Bearings and housings
. Floating design of mainshaft gear
. Narrower gear teeth width required

Question 25

what type of synchronizer is a multi piece unit composed of a central hub, two soft metal blocker rings, a shift collar. a set of inserts and two insert springs

Answer 25

block type synchronizer

Question 26

what is the first reduction device used to increase the available engine torque

Answer 26

the transmission

Question 27

how is torque divided in a twin countershaft design

Answer 27

it is split evenly between both countershafts 180 degrees apart

Question 28

how is torque divided in a triple countershaft design

Answer 28

between all three countershafts 120 degrees apart

Question 29

what are some advantages of multiple countershaft transmissions

Answer 29

. smaller and lighter countershafts, bearings and housings
. floating design of mainshaft gear
. Narrower gear teeth width required

Question 30

how many reverse idler gears are needed in a multi countershaft design

Answer 30

one for each countershaft

Question 31

the mainshaft gears are located in place by

Answer 31

a set of double washers

Question 32

the shift lever directly moves what in the shift bar housing

Answer 32

shift rail

Question 33

multiple countershaft transmissions use several housings , these housings are kept in alignment through the use of .

Answer 33

precise dowelling