401F a&b: Transmission Service Flashcards
what would damaged torsional springs in the clutch cause
vibration or gear rattle complaint
what would driveline vibrations cause in the transmission
they would show up as gear rattle and are transmitted to the driver through the shift lever
what would driveline vibrations also cause
leaking output shaft seal and worn output shaft bearings .
what would gear shifting components that are loose, binding or out of adjustment cause
gear clashing and hard shifting
what are the common transmission complaints
vibration - slip out or jump out - hard shifting - gear clashing - excessive heat or noise
what is slip out or jump out
when the transmission moves to neutral on its own
when does slip out or jump out tend to occur
when torque is being applied to the drive line
some conditions that lead to slip out are
.transmission mounted eccentrically with the fly wheel pilot bearing
.worn mainshaft and out put shaft bearings
.insufficient pressure on the detent ( weak springs )
.excessive wear on the detent notch/ shift rail
.incorrect adjustment or excessive wear in the remote shaft linkage
when is jump out likely to occur
during rough or normal road conditions when there is no load on the driveline
what are some conditions that will cause jump out
. extra heavy and long shift levers that swing during operating over uneven terrain
. excessive movement between the transmission and shift linkage forcing the transmission out of gear
. weak or broken detent springs
what would cause hard shifting
the external shift linkage or the internal transmission components
what are some external linkage problems
. worn connections or bushings
. binding or improperly adjusted linkage
. lack of lubrication on the joints
. anything that obstructs the free movement of the shift lever
problems for hard shifting that occur inside the transmission are
. a twisted mainshaft . bowed or broken mainshaft key . cracked housing . overtorqued shift block lock screws . sprung yoke bar . swelled areas of the yoke bar
what might cause hard shifting in first gear and reverse ONLY
that the first reverse spring-loaded plunger is not adjusted properly or is burred resulting in restricted movement
what will no properly double clutching between gears cause
gear clashing
what would be the problem if gear clashing occurs during shifting into first or reverse
incorrect clutch adjustment
what damage would be caused by a damaged/maladjusted clutch brake that is not working properly
the input shaft will not stop rotating and cause gear clashing
what are whine or squeal noises caused by
insufficient gear clearance or backlash
what would a growling noise be caused by in the transmission
damaged gear teeth or improper timing and improper installation of the countershaft gears
what would operating the transmission on a more than 12 degree slope cause
excessive heat due to lack pf lubrication
why should you never let the transmission hang by the input shaft
clutch disc damage will occur
why should you check the service manual before removing the cover during the shift tower removal
to see if the detent balls and springs will fly out at you
why should you change the oil in a transmission 24 to 100 hours after installation
because the components lap together and will cause excessive wear particles
what is Frosting
micro-pitting that appears as a band of off white discoloration formed in the middle of the tooth
what is off set frosting
micro-pitting that forms on one side of the gear tooth
what is healing
when mating teeth wear into each other and polish out the frosting . at this time no further wear will take place
what causes spalling in gear teeth
when the gear is subject to an extreme overload condition
scoring and galling is caused by
insufficient oil film between mating teeth resulting in very high surface temperatures causing welding and tearing of the gear teeth surface
what damage would sever shock loading or foreign object passing through the gear mesh cause
impact fractures
fatigue fractures are caused by
high stress over a period of time . can be identified by beach marks on the fractured area
what are stringers or gas pockets
weak points in the gear itself
when ever its determined that a gear must be replaced you must also
replace its mating gear
premature input shaft bearing failure or slip out in direct gear is often an indication of a problem with
engine and transmission mounts
leaking output shaft seals, worn output shaft bearings and broken synchronizer pins are often an indication of a problem with the
driveline
worn input shaft splines that do not let the clutch fully release, cause gear clashing in which gears
first and reverse
a power take off with mismatched gear sets or insufficient gear back lash will cause
whine or squeal
why must the mating driveline parts be carefully marked before you disconnect the driveline
this will ensure that the driveline phasing and balancing will not be changed
on a selective main shaft assembly, improper shimming could result in which two failures
too little running clearance do not provide proper lubrication
too much clearance causes excessive rattling due to vibrations
what will improper installation of the dowels between the mainshaft housing and auxiliary housing will lead to
a misalignment problem and accelerated wear on components
When could a shift lever slip out from gear?
During normal acceleration or deceleration
Operator Complaint: Apply clutch pedal to shift and its hard to shift, grinding gears. What could be the fault?
Seized Pilot Bearing
If a pilot bearing is seized what will happen when the clutch pedal is depressed?
No break in path of power, shaft continues to spin, cannot shift
Why is end play important?
Allows for expansion
Does the countershaft or mainshaft need more thrust washers?
Mainshaft needs more
What type of bearings are used to support the mainshaft?
Anti-Friction bearings
What is the main purpose of the thrust washers? (wear)
Reduce gear wear
A blocker ring is usually made of what material?
Brass/Bronze
Operator complains about grinding gears when shifting quickly. What could be the fault?
Damaged/Failed synchronizer
Operator complains that shifting is becoming difficult. The technician finds the boot is torn on the shift lever assembly, what could be the fault?
Contamination around moving parts in the lower lever
If a transmission breather clogs, what could be a result?
Input/Output seals fail - leak
Jump out can be caused by worn detents or?
Long shifter
Slip out can be caused by worn detents, worn linkage or?
Clutching teeth are worn out or a worn fork/collar
What are the two types of gear teeth on sliding clutches?
Dove tail or straight cut
What gears usually use a dove tail gear tooth on the sliding clutch?
4th and 5th
Do auxiliary transmissions use helical cut gears or straight cut gear?
Helical gears to handle torque
Operator complains of a whine/squeal, what could be the cause?
Insufficient clearances
PTO w/out backlash
mix matched gears
What could cause a transmission to get stuck in gear?
twisted mainshaft worn shift tower housing worn input shaft splines misadjusted clutch/clutch brake counter shaft brake
What are some things that should be visually inspected when there is a transmission fault?
Engine and Transmission mounts
Clutch system condition
driveline condition
shift mechanism operation
If an operator regularly coasts down hill with the clutch pedal depressed, what could be the fault they are causing?
Over heating
True or False
A vehicle being driven under 32km/h constantly will have no faults?
False - unless adequate coolers are used
What are three things that can cause a transmission to growl?
Broken gear teeth
Incorrect timing - will show up immediately after rebuild
Bad Bearings
What type of bearing(s) support a mainshaft?
1 friction and 1 anti-friction
What causes spalling on transmission gear teeth?
Overloading over a short period of time
What can cause gear clash?
Improperly adjusted clutch
damaged clutch brake
seized pilot bearing
damaged splines on shaft
A gear rattle can be cause by?
A rough running engine
True or False.
Frosted gears should be replaced immediately?
False - normal wear
True or False
Initial pitting is mild, usually 0.030” depth?
True
What is used to measure clearance between gears on a selective mainshaft?
feeler blades
Where would a selective washer be found on a NON-selective mainshaft assembly?
For reverse gear
Chassis air supply pressure is at a minimum of?
90 PSI
What is the final check on a transmission overhaul?
Road test - Leak check
A green or blue plugs might be an indication of what in the transmission?
Synthetic oil
After refiling a transmission with oil, when should oil level be rechecked?
After letting the engine run for a short period to fill the cooler and after the road test
How large should a buffer zone be around a diesel electric hybrid?
1 m all around
Who can repair hybrid vehicles?
Trained/certified personnel
A “00” glove class is good to what voltage rating?
0.5kV
A “4” glove class is good to what voltage rating?
36.0kV
What must be worn over insulated rubber gloves when working with high voltage?
Leather protectors
How often should protective gloves be checked?
Every use
What air pressure is needed to activate the splitter cylinder?
58-63 PSI
Upstream from the air filter/regulator, what should air pressure be (minimum)?
90 PSI
How low does the voltage need to be before working on High voltage system?
Below 30 volts
How is gas charge from an accumulator vented?
Connect a proper venting tool
How many groves are on a non-selective main shaft?
3 groves
