- Clutch
- The assembly that connects and disconnects engine power to a manual transmission; a pressure plate clamps a friction disc to the flywheel to transmit torque.
- Flywheel
- A heavy disc bolted to the crankshaft; its machined face is the friction surface the clutch disc clamps against, and it stores rotational energy to smooth power pulses.
- Clutch (friction) disc
- The plate splined to the transmission input shaft, clamped between the flywheel and pressure plate, that transmits engine torque when engaged.
- Pressure plate
- A spring-loaded cover assembly bolted to the flywheel; its diaphragm spring clamps the clutch disc, and pressing the release fingers unclamps it.
- Diaphragm spring
- The cone-shaped spring in a pressure plate; its fingers are pushed by the release bearing to unclamp the disc, and it sets the clamping load.
- Release (throwout) bearing
- Rides on the input-shaft hub and pushes the pressure plate's spring fingers when the pedal is pressed, disengaging the clutch; rattles in neutral with the pedal down when worn.
- Pilot bearing
- A small bearing or bushing in the crankshaft (or flywheel) that supports the front of the input shaft; makes noise only with the clutch released and the transmission in gear.
- Clutch fork
- The lever that moves the release bearing toward the pressure plate, actuated by a cable or a hydraulic slave cylinder.
- Clutch master cylinder
- In a hydraulic clutch, the pedal-operated cylinder that generates hydraulic pressure and sends it to the slave cylinder.
- Clutch slave cylinder
- Receives pressure from the master cylinder and converts it to mechanical force on the clutch fork or release bearing to disengage the clutch.
- Mechanical (cable) clutch
- A clutch actuated by a cable from the pedal to the fork, rather than by hydraulic master and slave cylinders.
- Pedal free play
- The small amount of pedal travel before the release bearing contacts the spring fingers; too little keeps the bearing loaded and causes slip and bearing wear.
- Clutch slipping
- Engine rpm rises but the vehicle doesn't accelerate to match; caused by worn or oil-soaked facings, a weak pressure plate, a glazed flywheel, or no free play.
- Clutch chatter (shudder)
- A vibration felt during clutch take-up; caused by a glazed or oil-contaminated disc, a warped flywheel, or worn engine/transmission mounts.
- Clutch drag
- Failure of the clutch to fully release, so the disc keeps spinning; causes grinding into several gears and hard shifting from a stop.
- Dual mass flywheel (DMF)
- A two-piece flywheel with internal springs that damp drivetrain vibration; worn springs cause an idle rattle and a rocking sensation on start-up and shutdown.
- Flywheel runout
- The face (lateral) wobble of the flywheel measured with a dial indicator; excessive runout causes clutch chatter and may prevent full release, so resurface or replace.
- Oil-contaminated clutch disc
- Friction facings soaked with oil (often from a leaking rear main seal); the disc can't grip, so it must be replaced and the leak repaired before reassembly.
- Pilot-bearing noise test
- Noise present with the clutch released and the transmission in gear at a stop indicates the pilot bearing, because the input shaft and crankshaft turn at different speeds.
- Release-bearing noise test
- Noise in neutral with the pedal fully down indicates the release bearing, which is still spinning against the diaphragm-spring fingers.
- Clutch alignment tool
- A splined tool used to center the clutch disc on the flywheel pilot before tightening the pressure plate, so the input shaft can enter the disc and pilot bearing.
- Self-adjusting clutch
- A clutch with a mechanism that automatically compensates for disc wear, keeping pedal free play and release point consistent.
- Glazed clutch disc
- A hardened, shiny friction surface caused by excess heat and slipping; reduces grip and causes shudder and slipping.
- Clutch linkage adjustment
- Setting cable or hydraulic free play so the clutch fully engages (no slip) and fully releases (no drag) within pedal travel.
- Bleeding a hydraulic clutch
- Removing air from the master/slave system; air causes a soft pedal and incomplete release, so the system is bled until the pedal is firm.
- Throwout bearing free travel
- Clearance that keeps the release bearing off the spring fingers when the pedal is up; loss of it loads the bearing and causes slip and premature wear.
- Clutch cover assembly
- Another name for the pressure plate: the cover, diaphragm (or coil) springs, and release levers that clamp the disc to the flywheel.
- Resurfacing the flywheel
- Machining the flywheel face flat and true when installing a new clutch, to remove glazing, heat checks, and runout.
- Coil-spring vs. diaphragm pressure plate
- Coil-spring (Long/Borg & Beck) types use multiple coil springs and release levers; diaphragm types use one cone spring and are more common today.
- Symptom: vehicle creeps with pedal fully down
- Indicates the clutch is not releasing (drag) — often from a warped disc, no free play, air in the hydraulics, or a binding pilot bearing.
- Manual transmission
- A gearbox in which the driver selects gear ratios by hand, routing engine torque through pairs of meshing gears of different tooth counts.
- Input shaft
- Carries engine torque from the clutch into the transmission; it drives the countershaft and the constantly meshed speed gears.
- Countershaft (cluster gear)
- Carries power from the input shaft up to the mainshaft speed gears, providing the gear pairs that create each ratio.
- Mainshaft (output shaft)
- Carries the speed gears that the driver locks to it through synchronizers; delivers the selected ratio to the driveshaft or final drive.
- Synchronizer
- Uses a friction-cone blocker ring to match a gear's speed to the sliding sleeve before the dog teeth engage, preventing clash.
- Blocker (synchronizer) ring
- The friction cone that rubs a gear's cone to equalize speeds during a shift; wear causes grinding into that one gear.
- Synchronizer sleeve
- The sliding collar the shift fork moves; once speeds match, it slides over the gear's dog teeth to lock the gear to the shaft.
- Dog teeth (engagement teeth)
- The teeth on a speed gear that the synchronizer sleeve engages; rounded dog teeth let a gear pop out under load.
- Shift fork
- A pronged component on a shift rail that straddles a synchronizer sleeve and slides it along the shaft to engage or disengage a gear.
- Shift rail
- The rod that the shift fork is mounted on; moved by the shifter, it carries the fork to engage a gear and is held by a detent.
- Detent
- A spring-loaded ball that seats in a notch on the shift rail to hold the rail in its selected position; a weak detent lets the transmission jump out of gear.
- Interlock
- A mechanism that prevents two gears from engaging at once by locking the other shift rails when one is moved.
- Gear ratio
- Driven (output) tooth count divided by drive (input) tooth count; a ratio above 1 is a reduction, below 1 is overdrive.
- Reduction (underdrive)
- A gear ratio greater than 1:1 where the output turns slower than the input, multiplying torque (for example, first gear).
- Overdrive
- A gear ratio below 1:1 where the output turns faster than the input, lowering engine rpm for highway cruising.
- Combining stage ratios
- When power passes through more than one gear pair, the overall ratio is the product of the stage ratios (multiply, don't add).
- Reverse idler gear
- An extra gear inserted in the reverse power path to reverse output direction; many reverse gears are not synchronized, so a grind on reverse is common.
- Helical gears
- Gears with angled teeth that mesh gradually for quiet, strong operation; used for the constantly meshed speed gears in modern transmissions.
- Spur gears
- Gears with straight teeth; simpler and used for sliding reverse gears, but noisier than helical gears.
- Symptom: grinds into one gear
- Points to a worn or cracked blocker ring (synchronizer) for that specific gear.
- Symptom: grinds into several gears
- Points to a clutch that is not fully releasing (free-play, air, drag), keeping the input shaft spinning.
- Symptom: pops out of gear under load
- Points to a weak detent, worn shift forks, rounded dog teeth, excessive endplay, or worn engine/transmission mounts.
- Symptom: hard shifting from a stop
- Points to clutch drag, a dragging pilot bearing, binding shift linkage, worn synchronizers, or cold/wrong-viscosity gear oil.
- Symptom: whine in neutral, gone in gear
- Points to the input shaft or countershaft bearing — parts turning at engine speed in neutral.
- Endplay
- The axial (in-and-out) free movement of a shaft; excessive endplay lets gears partially disengage and causes noise and jump-out.
- Bearing preload
- A controlled amount of load applied to a bearing (often via shims) so it has no play; set to specification on shafts and pinions.
- Gear oil (GL rating)
- Lubricant for manual gearboxes; API GL ratings indicate the EP additive level — use the manufacturer-specified viscosity and rating.
- Shift linkage bushings
- Wear points in the external shifter linkage; worn bushings cause sloppy or hard shifting and missed gears.
- Bellhousing
- The housing that bolts the transmission to the engine and encloses the clutch and flywheel; misalignment causes release and noise problems.
- Power flow
- The path torque takes through the engaged gears for a given gear selection; tracing it explains which parts are loaded in each gear.
- Transaxle
- A unit that combines the transmission, final drive, and differential in one housing, used in transverse front-wheel-drive vehicles.
- Transaxle vs. transmission
- A transaxle includes the differential and final drive in its case and drives two half-shafts; a transmission drives one shaft to a remote axle.
- Final drive
- A fixed gear reduction between the transmission output and the differential; it multiplies torque and sets the overall ratio after the selected gear.
- Helical final-drive gears
- Parallel helical gears used in a transverse transaxle, since the engine and axles are already in line and power need not turn 90 degrees.
- Transaxle input shaft
- Transmits engine power from the clutch into the transaxle for gear selection.
- Transaxle differential
- The differential built into the transaxle case that splits drive to the two front half-shafts and lets the wheels turn at different speeds.
- Half-shaft (axle shaft)
- A drive shaft, fitted with CV joints, that delivers torque from the transaxle differential to a front wheel.
- Symptom: whine that tracks vehicle speed
- In a transaxle, points to the final-drive or differential gears, which turn with the axle shafts; the noise persists while coasting in neutral.
- Symptom: noise that tracks engine speed
- In a transaxle in neutral, points to the input shaft or its bearing.
- Symptom: vibration while driving (FWD)
- Often points to worn CV joints on the half-shafts; inspect the boots and joints.
- Transaxle case
- The housing that encloses and protects the gearsets, final drive, and differential of a transaxle.
- Differential pinion (spider) gears
- The small gears in the differential case that mesh with the side gears, allowing the two driven wheels to turn at different speeds.
- Differential side gears
- The gears splined to the axle shafts (or half-shafts); driven by the spider gears, they transmit torque to each wheel.
- Ring gear (transaxle)
- The large final-drive gear bolted to the differential case; driven by the final-drive pinion, it turns the whole differential assembly.
- Transaxle mounts
- Rubber mounts that locate the transaxle and damp vibration; worn mounts cause clunks and can lead to gear jump-out.
- Inner CV (tripod) joint
- The plunging inboard joint on a half-shaft that absorbs length change as the suspension moves while transmitting torque to the transaxle.
- Outer CV joint
- The fixed (Rzeppa, ball-type) joint at the wheel end of a half-shaft that allows steering angle while delivering constant-velocity torque.
- Transaxle fluid level check
- Verifying gear-oil level via the fill/check plug; low fluid causes whine, hard shifting, and premature gear and bearing wear.
- Harsh shifting in a transaxle
- Often a synchronizer issue; inspect the blocker rings and shift mechanism, and confirm clutch release and fluid condition.
- Transverse engine layout
- An engine mounted sideways so the crankshaft is parallel to the axles; pairs naturally with a transaxle in front-wheel drive.
- Driveshaft (propeller shaft)
- The shaft that carries torque from the transmission to the rear axle in a rear- or four-wheel-drive vehicle, fitted with universal joints.
- Universal (U) joint
- A cross-and-bearing (Cardan) joint that lets a driveshaft transmit torque through small angle changes; output speed fluctuates at angle, so joints are paired.
- Slip yoke
- A splined yoke at the front of a driveshaft that slides in and out of the transmission to accommodate length change from suspension movement.
- CV (constant-velocity) joint
- A joint that delivers a constant output speed through large, changing angles, used on FWD and independent-rear half-shafts.
- Rzeppa joint
- A ball-and-cage outer CV joint that allows large steering angles while transmitting torque at constant velocity.
- Tripod (tripot) joint
- A plunging inner CV joint using three rollers on a spider, allowing the half-shaft to change length as the suspension moves.
- CV boot
- The flexible rubber cover that retains grease and keeps dirt out of a CV joint; a torn boot is the leading cause of CV-joint failure.
- Symptom: clicking on sharp turns
- The classic sign of a worn outer CV joint on a front-wheel-drive vehicle.
- Symptom: clunk on acceleration/deceleration
- Often a worn inner (plunging) CV joint, or a worn U-joint on a rear-wheel-drive driveshaft.
- Symptom: vibration that rises with speed (RWD)
- Points to a worn or binding U-joint, a bent or unbalanced driveshaft, or an incorrect driveline angle.
- Driveshaft balance
- Balance weights keep a spinning driveshaft from vibrating; lost weights or built-up undercoating cause a speed-related vibration.
- Driveline (pinion) angle
- The working angle of the U-joints set by the transmission and pinion positions; an incorrect angle causes vibration and accelerated U-joint wear.
- Center support bearing
- A rubber-mounted bearing supporting a two-piece driveshaft at its midpoint; when worn it causes vibration and a clunk.
- Constant velocity vs. universal joint
- A CV joint keeps output speed constant through large angles; a U-joint's output fluctuates at angle, so U-joints are paired to cancel it.
- Yoke
- The forked driveshaft end that holds a U-joint cross; a slip yoke also allows length change, while a flange yoke bolts to a companion flange.
- Companion flange
- The flange on the differential pinion (or transmission) that the driveshaft yoke bolts to.
- Phasing (U-joint)
- Aligning the two U-joint yokes on a driveshaft in the same plane so their speed fluctuations cancel; out-of-phase joints cause vibration.
- Half-shaft removal
- Service step to replace a CV joint or boot; the hub nut and joints are freed so the shaft can be pulled from the transaxle.
- U-joint replacement
- Pressing out the old cross and bearing caps and installing new ones; checked for binding so the joint moves freely after assembly.
- Grease (CV/U-joint)
- Special joint grease packed into CV joints and serviceable U-joints; loss of grease through a torn boot leads to wear and noise.
- Drive axle
- The assembly that delivers torque to the wheels through the ring-and-pinion final drive and the differential.
- Differential
- A gear set that splits torque between two drive wheels while allowing them to rotate at different speeds, as needed when cornering.
- Ring and pinion
- The final-drive gear set in a drive axle: the pinion drives the larger ring gear, setting the axle ratio and turning power to the axle shafts.
- Hypoid gear set
- A bevel ring-and-pinion with the pinion offset below the ring-gear centerline; turns driveshaft power 90 degrees and needs extreme-pressure (EP) gear lube.
- Axle ratio
- The ring-gear teeth divided by the pinion teeth (for example, 3.73:1); a numerically higher ratio gives more torque but higher engine rpm.
- Backlash
- The clearance between the meshing teeth of the ring and pinion; set to specification, it prevents binding and gear noise.
- Pinion depth
- How far the pinion is set into mesh with the ring gear, adjusted by shims; wrong depth produces an incorrect contact pattern and gear howl.
- Gear-tooth contact pattern
- The marking compound pattern on the ring-gear teeth used to verify correct pinion depth and backlash during a differential setup.
- Pinion bearing preload
- The controlled load on the pinion bearings, set by a crush sleeve or shims; too little allows play and noise, too much overheats the bearings.
- Crush sleeve (collapsible spacer)
- A spacer between the pinion bearings that is crushed to set pinion bearing preload; replaced whenever the pinion nut is loosened.
- Open differential
- A standard differential that sends equal torque to both wheels but spins the wheel with the least traction.
- Limited-slip differential (LSD)
- Uses clutches, cones, or gears to resist a large wheel-speed difference, biasing torque to the wheel with traction.
- Locking differential (locker)
- A differential that can lock both axle shafts to turn together for maximum traction in low-grip conditions.
- Friction-modifier additive
- An additive required by many clutch-type limited-slip differentials to prevent chatter and clunk during slow turns.
- Differential side (axle) gears
- The gears splined to the axle shafts; driven by the spider gears, they deliver torque to each wheel.
- Spider (pinion) gears
- The small gears on the cross shaft inside the differential case that mesh with the side gears to allow different wheel speeds.
- Axle shaft
- The shaft that carries torque from the differential side gear to a drive wheel; supported by bearings in the axle housing.
- C-clip axle
- A rear axle retained inside the differential by a C-shaped clip; the differential must be opened to remove the axle shaft.
- Bearing retainer (pressed-on) axle
- A rear axle held by a pressed-on bearing and retainer plate at the housing end, removed without opening the differential.
- Axle endplay
- The in-and-out free movement of the axle shaft; set to spec by shims or the bearing design to prevent noise and seal wear.
- Pinion seal
- The seal around the pinion at the companion flange; a leak shows as gear-oil at the front of the differential and can lower fluid level.
- Axle (wheel) seal
- The seal at the end of the axle housing that keeps gear oil in and contaminants out; a leak can soak the brakes.
- Symptom: whine that rises with vehicle speed
- Points to worn ring and pinion or incorrect backlash/preload in the drive axle.
- Symptom: clunk on take-up or direction change
- Points to excessive backlash or worn side/spider gears in the differential.
- Symptom: chatter on slow turns
- Points to the wrong fluid or a missing limited-slip friction-modifier additive.
- Symptom: howl that differs drive vs. coast
- Points to an incorrect pinion depth or gear-tooth contact pattern.
- Carrier (differential case)
- The housing that holds the spider and side gears and to which the ring gear bolts; it rotates with the ring gear.
- EP gear lubricant
- Extreme-pressure gear oil required for hypoid axles because of the high sliding tooth contact between ring and pinion.
- Setting backlash
- Adjusting side shims or bearing adjusters to move the ring gear, achieving the specified ring-and-pinion backlash.
- Drive vs. coast side of gear tooth
- The drive side carries torque under power, the coast side under deceleration; the contact pattern is read on both during setup.
- Four-wheel drive (4WD)
- A system, usually with a transfer case and high/low ranges, that drives all four wheels; often part-time and intended for low-traction use.
- All-wheel drive (AWD)
- A full-time system that drives all four wheels through a center differential or coupling, so it can stay engaged on dry pavement.
- Transfer case
- The gearbox in a 4WD vehicle that sends power to both front and rear axles and provides high and low gear ranges.
- Low range
- A transfer-case gear range that multiplies torque for off-road, towing, or steep grades at low speed.
- High range
- The normal transfer-case range used for everyday on-road driving in a 4WD vehicle.
- Part-time 4WD
- A system that locks the front and rear axles together with no center differential; must be used only on loose or slippery surfaces.
- Full-time AWD
- A system with a center differential or viscous coupling that allows a front-to-rear speed difference, so it can run on dry roads.
- Center differential
- A differential between the front and rear drivelines that lets the axles turn at different speeds, preventing driveline wind-up in AWD.
- Driveline (axle) wind-up
- The torque bind (crow-hop) when part-time 4WD is engaged on a high-traction surface, because the locked axles can't turn at different speeds in a turn.
- Viscous coupling
- A silicone-fluid clutch that transfers torque between front and rear when a speed difference develops; common in AWD systems.
- Locking hubs
- Front-hub devices on some part-time 4WD vehicles that connect or disconnect the front wheels from the axle shafts to save wear and fuel in 2WD.
- Transfer-case chain drive
- A chain inside many transfer cases that transfers power to the front output shaft; a worn chain causes noise and slack.
- Shift-on-the-fly
- A 4WD feature allowing engagement between 2WD and 4WD high while moving, via electric or vacuum actuation.
- Front differential (4WD)
- The differential in the front axle of a 4WD/AWD vehicle that splits torque to the front wheels and allows them different speeds.
- Front driveshaft
- The shaft that carries power from the transfer case to the front differential in a 4WD vehicle.
- Symptom: clunk/bind turning on dry pavement (4WD)
- Normal driveline wind-up when part-time 4WD is engaged on high-traction surfaces — disengage 4WD, not a component failure.
- Symptom: 4WD won't engage
- Check the shift actuator (vacuum/electric), the transfer-case linkage, the front-axle disconnect or locking hubs, and the control module.
- Transfer-case fluid
- The lubricant specified for the transfer case (gear oil or ATF, per the maker); low or wrong fluid causes noise and chain/gear wear.
- Limited-slip vs. locking differential
- A limited-slip biases torque smoothly to the wheel with grip; a locking differential rigidly locks both wheels to turn together for maximum traction.
- Front-axle disconnect
- A mechanism that disconnects the front axle shaft in 2WD on some 4WD vehicles to reduce drag and wear, reconnecting when 4WD is selected.
- Torque-on-demand (active) AWD
- An AWD system that uses an electronically controlled clutch to send torque to the secondary axle only when wheel slip is detected.
- Wet vs. dry clutch (clutch-type LSD)
- Limited-slip clutch packs run in gear oil (wet); the friction-modifier additive in that oil controls their engagement and prevents chatter.
- Posi-traction
- A common trade name for a clutch-type limited-slip differential that drives both wheels for added traction.
- Spline
- The grooved coupling on a shaft (input shaft, axle, slip yoke) that transmits torque while allowing axial movement.
- Throw-out fork pivot
- The ball stud or pivot the clutch fork rocks on; a worn pivot causes erratic release and noise.
- Clutch pedal position sensor
- A switch/sensor that tells the engine controller the clutch is pressed (for starting and cruise control), and can affect start permission.
- Concentric slave cylinder (CSC)
- A hydraulic slave cylinder built around the input shaft that also serves as the release bearing; replaced as a unit when leaking.
- Input shaft bearing
- Supports the input shaft in the transmission case; when worn it whines in neutral with the engine running and clutch engaged.
- Snap ring
- A retaining ring that locates gears, bearings, or CV joints on a shaft or in a bore; used throughout drive-train assemblies.
- Thrust washer
- A flat bearing surface that controls axial play and carries thrust loads between rotating gears or the differential side gears.
- Cross shaft (differential)
- The shaft (pin) the spider gears ride on inside the differential case, retained by a pin or bolt.
- Marking compound (Prussian blue)
- Gear-marking paste applied to ring-gear teeth to reveal the contact pattern when setting up a differential.
- Driveshaft runout
- Radial wobble of the driveshaft measured with a dial indicator; excessive runout (bent shaft) causes a speed-related vibration.
- U-joint bind
- A stiff spot in a universal joint from worn or dry needle bearings; causes vibration and accelerates failure.
- Needle bearings (U-joint)
- The small roller bearings in each U-joint bearing cap that let the cross pivot; loss of grease leads to wear and a clunk.
- Plunge (inboard CV)
- The in-and-out movement an inner tripod CV joint allows so the half-shaft length can change with suspension travel.
- Axle bearing noise
- A growl or rumble that changes with load (lifting on a curve loads the opposite bearing) and tracks vehicle speed; indicates a worn axle bearing.
- Sealed transmission
- A gearbox with no dipstick; fluid level is checked at a fill/check plug at the specified temperature and procedure.
- Shift detent spring
- The spring behind the detent ball; weakened, it lets the rail creep out of its notch so the transmission jumps out of gear.
- Reverse lockout
- A mechanism (ring or lift collar) that prevents accidental engagement of reverse while driving forward.
- Clutch safety (start) switch
- A switch that only allows the starter to crank when the clutch pedal is fully depressed.
- Bellhousing alignment (dowels)
- Locating dowels that center the transmission to the engine; misalignment causes input-shaft and release problems and bearing wear.
- Differential preload (carrier bearings)
- The load on the carrier (side) bearings set by shims or adjusters; correct preload keeps the ring gear stable under load.
- Axle housing
- The casing that holds the differential, axle shafts, and bearings, and contains the gear oil in a solid drive axle.
- Vacuum-actuated 4WD
- A 4WD engagement system that uses engine vacuum to shift the transfer case or front-axle disconnect; vacuum leaks cause non-engagement.
- Electric-shift transfer case
- A transfer case shifted by an electric motor/encoder under control-module command; faults set codes and prevent range changes.
- Center viscous coupling vs. center diff
- A viscous coupling transfers torque on slip with no mechanical lock; a center differential always allows a controlled front-to-rear speed difference.
- Tire-size matching (4WD/AWD)
- All tires must be matched in size and wear; mismatched tires create constant speed differences that bind the driveline and damage couplings.
- Companion-flange runout
- Wobble at the pinion flange that contributes to driveshaft vibration; checked when diagnosing a speed-related rear-axle vibration.
- Clutch disc marcel (cushion) springs
- Wavy springs between the disc facings that cushion engagement; worn ones cause harsh, grabby take-up.
- Torsional (damper) springs in a clutch disc
- Coil springs in the disc hub that absorb torsional shock and reduce gear rattle; broken springs cause a rattling noise.
- Synchronizer hub and keys
- The hub splined to the shaft plus the spring-loaded keys (inserts) that push the blocker ring against the gear cone during a shift.
- Gear whine vs. bearing growl
- Whine usually rises and falls with the gears in mesh (load/speed), while a bearing produces a rougher growl that tracks the shaft's rotation.
- Magnetic drain plug
- A drain plug with a magnet that captures metal particles; heavy metal on it signals internal gear or bearing wear.
- Axle bearing preload (tapered)
- The set load on tapered axle/pinion bearings; correct preload prevents both looseness (noise) and overheating.
- Half-shaft length difference (FWD)
- Unequal-length half-shafts (or an intermediate shaft) used to balance the layout and reduce torque steer in front-wheel drive.
- Intermediate shaft (FWD)
- A short shaft and support bearing between the transaxle and one front half-shaft, used to equalize shaft lengths.
- Boot clamp
- The band that secures a CV boot to the shaft and joint; a loose or failed clamp lets grease escape and the joint fail.
- Transmission mount
- A rubber mount that supports the rear of the transmission; when collapsed it changes driveline angle and causes vibration and clunks.
- Crush vs. shim pinion preload
- Pinion bearing preload is set either by a collapsible crush sleeve or by selectable shims with a solid spacer, depending on axle design.
- Carrier break (axle)
- The point in an axle line where a different carrier case is needed to accommodate certain ratio ranges of ring gear.
- Clutch judder vs. slip
- Judder is a vibration during engagement (contamination, glazing, mounts); slip is lost drive with rising rpm (worn facings, weak plate, no free play).
- Cardan joint
- Another name for a conventional universal (U) joint, named for its cross-and-bearing design.
- Double-Cardan (CV) driveshaft joint
- Two U-joints with a centering ball at one end of a driveshaft, used at steep angles to give near-constant velocity.
- Gear oil viscosity
- The grade (for example, 75W-90) specified for a gearbox or axle; using the wrong viscosity causes hard cold shifting or excess wear.
- Differential ratio identification
- Found by counting ring and pinion teeth, by a tag/code, or by turning the input one revolution and counting wheel turns.
- Bearing cup and cone
- The two parts of a tapered roller bearing: the cup (outer race) pressed in the housing and the cone (rollers + inner race) on the shaft.
- Axle wind-up under torque (leaf spring)
- Spring wrap that lets the axle rotate slightly under hard acceleration; can cause hop and U-joint angle change.
- Clutch break-in
- Gradual, moderate use of a new clutch to seat the friction surfaces; harsh early use can glaze or shock-load the disc.
- Technician A / Technician B item
- An ASE question format where you judge whether Technician A is correct, B is correct, both, or neither — read each statement as a separate claim.
