HET 4 DRIVE AXLE Flashcards
DRIVE AXLE ASSEMBLY FUNDAMENTALS ON-ROAD 190401h
What are the four functions of a drive axle assembly?
Support the weight
Last gear reduction
Change path of power 90°
Handle wheel speed differences
Type, size and number of drive axles depend on what?
Weight of vehicle and cargo
Amount of traction required
Final drive ratio
An axle code is D S 40 4 - P, what is the GAWR?
40 x 1000lbs = 40 000lbs is GAWR
GAWR stands for?
Gross axle weight rating per tandem x 1000 lbs
Axle code is DP581-P, what does the P stand for?
Standard lube pump
GVWR stands for?
Gross vehicle weight rating
-the total weight of the vehicle and its load
Axle codes second digit is a letter, what are the options that can be seen?
S - Single Reduction
P - Planetary double reduction
T - Dual Range
C - Single reduction with controlled traction differential
D - single reduction with wheel differential lock
A - single reduction with in axle speed sensing
GCWR stands for?
Gross combination weight rating
If more traction is needed what kind of axle is added to the vehicle?
another DRIVE axle
Does adding a second non-driving axle help increase traction?
No, helps increase weight that can be carried
Describe startability?
Percentage of grade at which a drivetrain system can start a loaded vehicle moving at an idle?
If the startability is at too high of the ration what would be the complaint?
continually down shifting, not utilizing top gear, sacrificing fuel economy
If the startability ratio is too low what is the complaint?
poor fuel economy
Does straddle mount or overhunt mount drive pinions handle the most torque load?
Straddle mount
Pinion drives are usually mounted in what drive axle component?
Carrier hoursing
Can full floating axle be removed with weight still going to the wheels of the vehicle?
Yes the wheels will carry the weight
Thrust screw prevents the bevel or the pinion gear from moving away?
The bevel from moving away from the pinion
Where is the trust screw positioned in relation to the pinon gear?
Exact opposite location
Where will the maximum thrust load and deflections be found between the bevel and pinion gear?
The exact opposite of the pinion gear
What are the two case halves of a differential that are bolted together?
flanged and plain
Is the bevel gear bolted to the flanged or plain case half?
Flanged
True or False
Bevel gear and input pinion are a matched set and must be changed together?
True
If preload has already been set between the pinion drive and bevel gear can backlash still be adjusted without affecting preload?
Yes if LH and RH bearing adjustment rings are moved in and out at the same rates.
What components are INSIDE the differential assembly?
Cross shaft, spider(pinion) and side gears, thrust washers
Which side of the differential case does the cross shaft fit into?
Plain case half
The spider gears on the cross shaft inside the differential assembly face in or out to the center of the cross shaft? (toe in or heel in)?
The toes are facing in towards the center of the cross shaft
True or False
Both side gears need to move at the same speed?
False
Which is the most common differential carrier used today?
Single Speed Single Reduction
Why would a high speed clutch plate have a chamfered edge on the splines?
To help the sun engage
Where is the first reduction always found in a differential?
Pinion to Ring gear
The bevel gear are attached to what in a planetary differential?
Bevel gear is attached to Internal/Ring gears
What usually shifts a two speed planetary differential?
Air solenoid or actuator
In a two speed planetary, high speed is selected. What is the gear ratio created?
Direct Drive
What is the differential assembly in a two speed planetary differential?
Differential assembly - Carrier
When cornering, what wheel will have to go faster to cover the same distance as the other wheel?
Outside wheel
If wheels that are cornering cannot achieve a speed difference what is the result?
Tire scuffing, steering difficulties
Two speed means what in relation to path of power?
Two paths of power available
What component supports drive gears in a two speed differential?
Cross shaft
If speed is lost at one wheel, what happens to the other wheel on that axle?
Gets the lost speed
What is the bevel gear RPM?
Sum of both wheel assembly speeds
If you are given an input speed, what else do you need to figure out what speed is getting to the wheel hubs?
Gear ratio
Why is the first drive axle oil change usually done after a short period?
To remove break in debris
What type of oil should be used in a drive axle?
Manufacture spec
At what angle should a standpipe be added to a drive axle to correct the oil level?
12° or more
When does a standpipe most likely need to be added to a drive axle to correct oil level?
if the drive axle is 12° or more
OR
if the vehicle is operating on steep grades normally
Since oil from the drive axle goes to the wheel ends what should be done during services (fluid changes)?
Tilt the axle to get oil out from wheel ends
When is a static seal used?
Non-moving parts
Dynamic seals are used with what components?
Over a moving part
ei. drive axles
After a service and drive axle oil has been changed, what should be done before final level check?
Drive the vehicles for a few minutes and then let settle for 5 minutes. Recheck level
What is the purpose of a breather on a drive axle?
To allow built up pressure to release
What causes an o-ring to fail in a inter-axle differential lock cylinder?
high pressure in the housing
Why is input shaft and output shaft end play important?
If out of spec can cause vibration and damage
What should be done before a road test to find faults?
Visual Inspection
Why should a technician be cautious when doing a plug swap on a drive axle?
High temp - Burns
What components need to be inspected to find a drive axle fault?
Wheels, Tires, Hubs
Driveline
Suspension
On a driver controlled differential lock how is it applied and released?
Air applied and spring released
When differential action is eliminated what happens to speed to the wheels?
Speed is evenly distributed to each drive wheel
Why would a steer axle be a drive axle?
To give more traction without adding another axle
When does a no-spin traction control make a ratcheting noise?
Normal - during cornering
True or False
A non-spin traction control does NOT replace a standard differential?
False - it does replace it
Where do the driven clutch & holdout rings spline to in a no-spin traction control?
To the drive axle side gear
What force holds the driven clutch & holdout ring to the spider & center cam?
Spring force
Where do the stub shafts on the spider in a no-spin traction control fit into?
The diff case
When cornering which wheel can overrun and unlock the no-spin traction control on that side?
The wheel that needs to go faster
How is a differential usually lubricated?
Splash is common, but pressure with a pump is possible
What throws the oil in a differential?
The bevel gear
What is most likely to fail first when the oil level is too low?
The bearings and seals
Where is an oil pump usually located on a drive axle?
usually on the inter-axle
Why is a lube pump needed on a inter-axle?
High location in the front carrier housing - poor lube
What is the normal filter system in a drive axle?
Magnetic plugs
What drives a lube pump in a drive axle?
Input shaft - always turning
Spinning a bearing with compressed air is totally okay?
NO
What should be used to clean internal components of a differential carrier and drive axle housing?
a) petroleum-based cleaning solution
b) steam cleaning/soapy water
c) varsol
a and c
When should bearings be replaced?
When they show excessive wear
Gear nest is?
Pinions, Side gears and cross shafts
True or False
Pinion bearings need to be pre-loaded
TRUE
How is pinion bearing pre-load measured?
Rotating Torque
What tool is used to find pinion bearing preload?
a) micrometer
b) spring scale
c) torque wrench
d) multimeter
b) spring scale and cord
Before removing a full floating axle, what should a technician do?
lock the lock collar
How is a full floating axle removed?
Loosen axle flange nuts, strike raised lugs with hammer
What are two ways to apply wheel lock assembly before servicing a drive axle?
Special bolt or shop air 80-120PSI to the shift cylinder at all time
At what temperature does drive axle oil start to oxidize?
104°C
What is the normal operating temperature of a drive axle?
71-104°C (160-220°F)
What temperature of drive axle oil is showing signs of a larger problem?
121°C
Does low level of oil or high level of oil cause over heating in a drive axle?
Both
What are some causing of overheating in a drive axle?
Low oil level
High oil level - foaming
Improper lube type
Failing oil pump
What can cause drive axle noise on turns?
Worn: diff side gears/pinions diff spiders diff thrust washers axle shaft splines
What can cause noise during cost in the drive line?
Usually noise is heard on drive, but quieter on cost
Pinion and ring gear is too tight - ADJUST to fix
Constant noise in a drive axle could be from?
Flat spot on pinion or ring gear Flat spot on bearings worn pinion splines worn axle shaft dowel holes worn hub stubs bent axle shaft
Why would mismatched tires cause a differential to have premature wear/failure?
The differential action is always working
Operator is complaining about a noise in the drive axle but the technician cannot find any faults in the drive axle, what could be causing the noise?
suspension
pg 9 190401i
Bearings in a drive axle should be installed dry and clean?
No, they should be lightly oiled
A technician during a driveline service find the pinon teeth are pitted on the drive side, what could be the cause?
Extreme/Severe service
or
Insufficient Lube
A customer complains about a constant noise when driving (on accelerator), tech finds a bent axle housing. What could be the cause?
Vehicle has been overloaded
Vehicle was in an accident
or Shock loaded
On an integral pinion: the new pinion etch mark says +4 but the old pinon had a -3 etch mark, how many shims would have to be added or taken away?
remove 0.007” of shims
On a removable pinion bearing retainer, the etch mark on the pinion says +4, how many shims would have to be added or taken away?
0.004” in shims will have to be added
Where is the pinon position spacer located on an integral drive pinion mounting?
Between the pinion gear and the bearing
Where is the pinion position shims located on a removable pinion bearing retainer?
Between the cage and the carrier housing
What is the direct indicator of backlash between the pinion and bevel?
Wear pattern
What would cause a excessive toe wear pattern?
Ring gear too far in
What would cause an excessive face wear pattern?
Pinion out too far
What would cause an excessive flank wear pattern?
Pinion to far in
What would cause an excessive heel wear pattern?
Ring gear out too far
How would you correct a wear pattern that has too much toe?
Move ring gear away from pinion
or
Increase backlash
How would a technician correct a wear pattern that is showing too much face?
Move the pinion IN and re-adjust ring gear for backlash
What would a technician do to correct a wear pattern that is showing too much flank contact?
Move the pinion out and re-adjust ring gear for backlash
If a pinion position is moved, what has to be done after?
Re-adjust ring gear backlash
What must a technician do to correct a wear pattern that is showing too much heel wear?
Move ring gear toward pinion
or
Decrease back lash
What can be considered the last adjustment?
Thrust Screw Adjustment
What is the purpose of the thrust screw behind the bevel gear?
To prevent the bevel gear from deflecting away from the pinion under head shock loads
Generally how much should a thrust screw be backed off after it seats on the bevel?
180° turn, 1/2 turn
At what speed does a bevel gear turn?
The average speed between the two wheels
When an inter axle is locked, what happens to torque and speed?
Unequal torque
Equal speed
What are the drive axles splined too?
Bevel Gears
What could be the cause of noise when driving?
Broken Teeth
How is nominal dimension figured out?
Crown centreline to pinon back edge
What could a spur cut bevel gear be in a differential?
Side gear
In a two speed planetary what speed is it in when the sun is held from rotation?
Low speed
When is the differential action of the inter-axle differential stopped?
When clutch teeth are engaged -Locked
What does the inter-axle differential allow between forward and rearward drive axle input pinions?
A difference in speed
When do the differential pinions STOP ROTATING in an inter-axle differential?
When there is NO speed difference between drive and side gear
When differential action is allowed to operate in an inter-axle what happens to torque?
Its divided equally between two axles
If a rearward axle on an inter-axle truck hits a patch of ice, what will happen to the forward axle?
The truck will be struck - due to the low friction on the rearward axle
How much torque is applied to each axle when the lock is applied in the inter-axle?
Half the torque to the front, half the torque to the rear in non slippery condition
Where is the internal ring in an outboard planetary held too?
Spindle
What is the output member on an outboard planetary?
Carrier
Where is the lube pump usually located in a drive axle?
ON the front diff carrier assembly
At what speed does a no-spin spider rotate?
Same speed as bevel gear
Does the operator have any control of lock or release of no-spin traction control?
No, automatic from springs
When is power transmitted through diff pinion gears?
All times
Name the 3 versions of a wheel lock?
Shift collar, Spring, Clutch disc
What is the last check done on a differential?
Backlash or Thrust bolt clearance
Why is root clearance important?
Space for lube
Describe backlash?
The clearance between two tooth profiles that are in mesh
One piece axle housing is also known as?
Banjo housing
How many gears are in a single speed, double reduction carrier?
4 gears
What should be checked after pinion bearing preload?
Carrier bearing preload
Should oil be added to the inter-axle differential after a overhaul?
YES
Does nominal dimensions measure from the front of the pinion gear or the back edge of the pinion gear?
Back edge
If an oil leak is found on a differential but the seals do not appear to be the cause, where could the oil be from?
Housing leak - from fatigue - overloading
A plug breather will cause?
Blown seals - leaking
When removing a full floating axle, the retaining nuts should be removed before hitting the axle flange?
No, just loosened
Before disassembly of a diff what should be measured?
backlash
Which is set first preload or end play in assembly?
End play must be removed
How is pinion preload created?
Crush Sleeve, Spacer, Shim
Describe side gear?
Spur cut bevel gear
If a thinner crush sleeve is used does the pinion have more preload or less preload?
More preload
Before removal of diff carrier, what should a tech do?
Secure Vehicle
Apply diff lock - air or mechanically
disconnect drive shaft
mark housings
What is important when deciding gear oil?
Ambient temp
Do housings use gaskets or RTV?
RTV sealant
What would be the operator complaint if differential thrust washers were worn?
Noise ONLY when cornering
True or False
A vehicle should be shut down and inspected if the temperature in the diff is less than 104°C?
FALSE
121°C or more
Shop air is considered what PSI?
80-120PSI
When removing a case half, what should a technician be aware of on a no-spin set up?
It is spring loaded, large bolts should be used to release pressure safely
A fractured tooth on the crown gear could be caused by?
Shock impact loading
True or False
The pinion gear tries to move away from the crown gear when under load?
False bevel tries to deflect
Not all carrier houses are identical, what can be done along with etch marks to find nominal distance of a pinion?
Special pinion depth measuring tools
Dial indicator, arbor, plunger, gauge plate
At what PSI should air be applied to the inter-axle differential shift collar to adjust shift fork and collar travel?
60PSI
On an integral drive pinion mounting, the old pinion mark is +2, the new pinion marking it -2, what size spacer/shim is needed?
+0.004
When checking pinion bearing preload with a spring scale, what must be done to the bearing cage?
while applying press force
What gear oils should not be used at temps below -40?
a) 0-76A
b) 0-76D
c) 0-76E
d) 0-76M
a and b
Should petroleum oil or synthetic oil changes be done more often?
Petroleum (conventional) will be done more often
What might be needed to remove a yoke?
a specific puller to prevent damaging the yoke
When should a inter axle differential be locked out?
slow speed
poor traction surface
On a vehicle with a differential and a outboard planetary final drive, how many reductions are being used?
two reductions
pinion to bevel
sun to carrier
The gear shift knob is called what when a transmission has an auxiliary transmission?
Master Air Control Valve
