chapter 7 diffs and axles
clutch based units (electrohydraulic application units)
Uses a computer-controlled pump
drive axle shafts and bearings (ball-type axle bearings)
are designed to absorb radial and axial end thrust loads
The adjustment of the ring and pinion gear set on a shim-style carrier is being discussed. Technician A says that increasing the size of both shims an equal amount will result in a reduction in carrier bearing preload. Technician B says that placing a thinner shim on one side of the carrier and a thicker shim on the other side of the carrier will affect the ring and pinion gear contact pattern. Who is correct?
b only
When discussing pinion flange inspection, Technician A says that a groove on the flange sealing surface requires replacement of the flange. Technician B says that excessive runout of the pinion flange could cause a vibration. Who is correct?
b only
diff operation
drive pinion drives the ring gear which is attached to the diff case, when going straight ahead: diff housing and its components rotate as an assembly and power is transferred equally to both wheels.
common sources of leaks
pinion seal axle housing axle seal abs sensor
ring and pinion gears
provide final gear reduction, transfer power 90 degrees to the wheels
drive pinion bearing preload (collapsible spacer method)
the pinion nut is tightened until the spacer collapses and applies a specific preload to the bearings
methods used in determining final drive ratio
using vehicle service manual, decipher the code on the tag attached to or stamped on the axle housing, compare the number of revolutions of the drive wheels with those of the drive shaft, count the number of teeth on the drive pinion gear and the ring gear
diff operation when turning a corner
wheels must travel at different speeds to prevent tire scrubbing, diff pinion gears "walk" around slower side gear and cause other side gear to turn faster, percentage of speed that is removed from one wheel is given to the other
When discussion rear axle operation, Technician A says that when a car is moving straight ahead, all differential gears rotate as a unit. Technician B says that when a car is turning a corner, the inside differential side gear is locked to the differential case, causing the outside side gear to rotate faster. Who is correct?
A only
When discussing the mounting of the drive pinion shaft, Technician A says that drive pinion shafts may be mounted in a long bushing. Technician B says that drive pinion shafts are held by two tapered roller bearings. Who is correct?
B only
When discussing the procedure for removing a differential unit, Technician A says that the same procedure should be followed on both a removable and integral carrier housing. Technician B says that the axle shafts must be removed before removing the differential case. Who is correct?
B only
When discussing the torque multiplication factor of the differential, Technician A says that all of the gears in a differential affect torque multiplication. Technician B says that there is a gear reduction as the power flows from the pinion to the ring gear. Who is correct?
B only
When discussing differential action, Technician A says that when a car is making a turn, the outside wheel must turn faster than the inside wheel. Technician B says that a locked differential may cause the car to slide around a turn. Who is correct?
Both A and B
When discussing differential lubricants, Technician A says that limited-slip differentials require a special lubricant. Technician B says that all RWD differential units require a special hypoid-compatible lubricant. Who is correct?
Both A and B
When discussing electrohydraulic limited-slip differentials, Technician A says that these differentials improve handling on slippery surfaces. Technician B says that these differentials limit the amount of differential action between the side gears. Who is correct?
Both A and B
When discussing gear ratios, Technician A says that they express the number of turns the driven gear makes compared to one turn of the drive gear. Technician B says that the gear ratio of a differential unit expresses the number of teeth on the ring gear divided by the number of teeth on the pinion gear. Who is correct?
Both A and B
When discussing the retention of axle shafts, Technician A says that some axle shafts are retained in the housing by a plate and bolts. Technician B says that some axle shafts are retained in the housing by a C-washer or clip. Who is correct?
Both a and b
A differential is being assembled. Technician A says that carrier bearing preload must be adjusted prior to making the pinion gear depth adjustment. Technician B says that if the pinion bearing preload is excessive, the pinion nut will need to be backed off until the correct preload is reached. Who is correct?
Neither A nor B
When discussing numerical final drive gear ratios, Technician A says that lower gear ratios allow for better acceleration. Technician B says that higher gear ratios allow for improved fuel economy but lower top speeds. Who is correct?
Neither A nor B
When discussing the different designs of rear axles, Technician A says that the bearings for full-floating shafts are located within the axle tubes of the rear axle housing. Technician B says that C-type retainer axles are held in place by a pressed retainer ring against the axle bearing. Who is correct?
Neither A nor B
When discussing different types of ring and pinion gear sets, Technician A says that with a hunting gear set, each tooth of the pinion will always return to the same few teeth on the ring gear each time the pinion rotates. Technician B says that when a nonhunting gear set rotates, any pinion gear tooth is likely to contact each and every tooth on the ring gear. Who is correct?
Neither A nor b
The differential's _______ gear meshes with the ______ gear, which is fastened to the differential case, which houses the _______ shafts and gears, which are in mesh with the ______ gears, which are splined to the drive axles.
Pinion / Ring / Pinion / Side
The types of gears currently used as differential gears are the ________ , and ________ gears.
Spiral bevel / ?
IRS axle shafts
Use two U or CV joints per axle to connect the axle to the differential and the wheels are equipped with linkages and control arms to limit camber changes outer portion is supposed by an upright or locating member that is also part of the suspension
types of noises (bearing whine)
a high pitched sound normally caused by a faulty pinion bearings
types of noises (gear noise)
a howling or whining of the ring and pinion gears caused by an improperly set gear pattern, gear damage, or improper bearing preload
types of noises (clunk)
a metallic noise heard when the throttle is quickly opened or closed while the vehicle is moving
types of noises (chatter)
a noise that is evident when the vehicle is making a turn and is accompanied by a vibration
A knocking noise is coming from a differential only when the vehicle is cornering. Technician A says that the differential side gears could be damaged. Technician B says that the noise could be due to damage on the ring gear teeth. Who is correct?
a only
When reviewing the procedure for setting backlash, Technician A says that backlash can be adjusted along with side bearing preload by loosening or tightening side bearing adjusting nuts. Technician B says that to decrease the amount of backlash, a thinner shim is normally installed on the ring gear side of the case and a thicker shim installed on the other side. Who is correct?
a only
While servicing a differential, Technician A says a special additive should be used in clutch-type limited-slip differentials. Technician B says to fill the differential approximately one inch below the opening to avoid foaming. Who is correct?
a only
types of noises (chuckle)
a rattling noise that sounds like a stick rubbing against the spokes of a bicycle wheel
types of noises (BEARING rumble)
a sound that is like marbles tumbling in a container
planetary and hypoid final drive assembly (planetary final drive assembly)
allows for a very compact transaxle design
hunting gear set
any given tooth on the pinion gear contacts all of the teeth on the ring gear before it meets the same tooth again, an example is 3.89:1, does not need to be aligned - any tooth on the pinion may mesh with any tooth on the ring gear
partial nonhunting gear set
any one tooth of the pinion gear will come in contact with some of the teeth on the ring gear each revolution, the gear set must be assembled with its index marks aligned, an exmaple is 3.5:1
differential bearings
at least four bearings are found in all differentials, the drive pinion and case bearings are typically tapered roller bearings, different forces are generated in the diff due to the action of the pinion gear
drive axle shafts and bearings (tapered roller axle bearings)
axle end thrust can be adjusted
When discussing the proper timing of a ring and pinion gear set, Technician A says that if the gear set does not have timing marks, it is a nonhunting gear set. Technician B says that if that there are timing marks, one tooth of the pinion gear may be grooved or painted and there will be a notch between two ring gear teeth. Who is correct?
b only
independent rear suspension
bolted to the chassis and does not move with suspension
While checking ring gear runout, Technician A says excessive runout requires the ring gear to be removed and a separate runout check must be made on the case. Technician B says if case runout is within specifications, the ring and pinion must be replaced. Who is correct?
both a and b
differential bearings (differential case)
can be adjusted side to side to provide proper backlash and side bearing preload, some designs use threaded bearing adjusted; others use selective shims and spacers for adjustments
Most limited-slip differentials use either a clutch pack , a ? , or a ? to limit the action of the differential.
clutch pack / ? / ?
differential assembly
contains the diff case which attaches to the ring gear, includes the side gears and diff pinion gear that allow wheels to turn at different speeds, axles transmit power from diff to the wheels
The drive side of a hypoid gear tooth is curved in a ________ shape, and the coast side of the tooth is ________ . The inner end of the teeth on a hypoid ring gear is known as the ________ and the outer end of the teeth as the ________ .
convex / concave / toe / heel
axle housing (integral carrier type)
diff assembly is mounted in and supported by the axle housing, it is sometimes called a Salisbury-type diff
nonhunting gear set
each tooth of the pinion gear will come in contact with the same teeth on the ring gear each revolution, the gear set must be assembled with its index marks aligned, an example ratio is 3.00:1
__________ differentials are speed-sensitive slip-limiting differential units that contain a clutch pack and a hydraulic pump.
gerodisc
pinion mountings (overhung-mounted pinion)
has two opposing tapered-roller bearings
pinion mountings (straddle-mounted pinion)
has two opposing tapered-roller bearings with a spacer between them, has a straight-roller bearing supporting it
clutch-based units (clutch pack type)
has two sets of clutches, each consisting of steel plates and friction plates the steel plates are splined to the diff case and fricition plates are splined to the side gears during cornering, the plates slip, allowing the wheels to turn at different speeds
rear axle housing
holds all other components and attaches to the vehicles suspension
Ring and pinion gear sets are usually classified as _______ , ________ , or _________ gears.
hunting / nonhunting / partial nonhunting
Rear axle housings can be divided into two groups: ________ carrier and _________ carrier.
integral / removable
clutch based units (clutch-based electronic limited-slip systems)
involve speed sensors, antilock brakes, and microcomputers to monitor slipping can be tuned for specific applications on and off road and at different speeds
planetary and hypoid final drive assembly (hypoid final drive assembly)
is quieter and stronger than other designs
final drive
located in the rear axle housing on RWD cars, located within the transaxle on FWD cars
The diagnosis of a limited-slip differential is being discussed. Technician A says a chattering sound while the vehicle is going straight indicates that the clutches are slipping. Technician B says that an inch-pound torque wrench can be used to check breakaway torque. Who is correct?
neither a nor b
When checking the pattern of a gear set, Technician A says that the markings on the coast side of the tooth are the most important. Technician B says that if the marking is toward the outside diameter of the ring gear, it is referred to as being toward the toe of the gear. Who is correct?
neither a nor b
When discussing drive axle inspection, Technician A says that axle flange runout can be measured with a dial indicator. Technician B says a damaged wheel stud can often be repaired by using a thread chasing tool. Who is correct?
neither a nor b
When examining a pinion gear, a marking "+2" is found on the small end of the gear, Technician A says that this indicates that the gear has been remanufactured. Technician B says that this indicates that 0.002 inches should be added to the measured nominal pinion depth shim. Who is correct?
neither a nor b
While discussing the cause of an oil leak in an axle housing, Technician A says if the fluid leaks past the threads of the drive pinion nut, the leak can be corrected by installing a copper washer under the nut. Technician B says fluid leakage past the stud nuts that hold the carrier assembly to the axle housing can be corrected by applying thread or gasket sealer on the threads and tightening the nuts to specifications. Who is correct?
neither a nor b
driver axle shafts and bearings (straight roller axle bearings)
only absorbs radial loads, the axle housing bears the end thrust
Gear ratios express the number of turns the _______ gear makes compared to one turn of the _______ gear it mates with.
pinion / ring
The three common configurations used as the final drives on FWD vehicles are ______ , ______ , and ______ .
planetary / helical / hypoid
driveline inspection
position a dial indicator against outer surface of the flange apply slight pressure to the center of the axle to remove axle end play, zero the indicator slowly rotate the axle one complete turn and observe the readings on the indicator compare the reading with specs inspect wheel studs in the flange and threads
limited slip differentials
provide more driving force to the wheel with traction when one wheel begins to slip, allow the wheels to rotate at different speeds when turning a corner, are sometimes called posi-traction, traction-lok, and posi-units
locked differentials
provides very limited differential action designed to provide both drive axles with same amount of torque, regardless of torque Detroit locker (most commonly used / ratcheting-type differential) Eaton automatic locking differential (MLocker is the most recent version) Spool (utilized by cars built for drag racing and drifting, features ring gear mounted to an empty diff case)
helical final drive assembly
requires the centerline of the pinion gear to be aligned with the centerline of the ring gear
types of noises (knock)
similar to chuckle, but louder and can occur in all driving modes
drive axle shafts and bearings (three-quarter and semi-floating axles)
the bearings are located inside the housing, this design is found on passenger cars and light trucks.
drive axle shafts and bearings (full floating)
the bearings are located outside the axle housing, they are usually found on heavy-duty applications
hypoid gears
the centerline of the drive pinion gear intersects the ring gear at a point lower than the centerline, they are commonly used in cars and light-duty trucks, their design allows for a lower vehicle height and more passenger room inside the vehicle
axle housing (removable carrier type)
the diff assembly can be removed from the axle housing as a unit / it is sometimes called a pumpkin-type
transaxle final drive gears and differntial
the diff operates basically the same as in a RWD axle (there is no 90-degree change in direction), the drive pinion is connected to the transmissions output shaft, the ring gear is attached to the diff case
gear ratios
the number of turns the drive gear makes compared to one turn of the driven gear it mates with. "Low" gears refer to high numerical gear ratios. "High" gear refers to low numerical gear ratios. gear ratios are usually selected to provide the best combination of performance and economy.
A straddle-mounted pinion gear is usually mounted on ________ bearings, whereas an overhung-mounted pinion is mounted on ________
three / two
gear-based units
use worm gears - react to change in torque at one of two shafts three different designs (torsen units / QUAIFE automatic biasing differential (ATB) / Detroit truetrac)
clutch based units (gerodisc (gerotor) differentials
uses a clutch pack and hydraulic pump pump is driven by the left axle shaft pumps output determines how much pressure is applied to the clutch pack the amount of tire slip determines the pressure delivered by the pump
drive pinion bearing preload (non-collapsible spacer method)
uses selective shims to set the proper preload
clutch based units (viscous clutch-type)
uses steel and friction clutch plates (relies on the resistance of high-viscosity silicone fluid for application) a difference in rotational speed causes the fluid to shear and allows one wheel to turn at a different speeds than the other one
clutch based units (cone type)
uses two cone clutches - one cone that has frictional material on its outer surface; the other one with a grooved inside surface, cones allow wheels to turn at different speeds during cornering (provides torque to both wheels during straight-ahead driving)
