Your FREE ASE T5 Flashcards 2026 – 200+ Cards

The pin on a solid front axle about which the steering knuckle and wheel pivot. Worn kingpins cause free play, wander, and shimmy.

The common heavy-truck steering gear in which balls circulate between the worm shaft and a ball nut to reduce friction and multiply effort.

A design that combines the steering gear and the hydraulic assist in one unit — the standard arrangement on most medium/heavy trucks.

Uses a separate hydraulic power cylinder mounted on the steering linkage to assist a conventional gear.

Engine-driven pump that supplies pressurized fluid for steering assist. A weak pump, low fluid, or air causes hard steering and noise.

The amount the steering wheel turns before the front wheels move. Excess comes from worn linkage, a worn gear, or loose bearings — causes wander.

The steering link connecting the pitman arm to the steering arm on the axle, transferring the gear's motion to the wheels.

The adjustable link connecting the two steered wheels so they turn together; the tie-rod sleeve is where toe is adjusted.

The arm splined to the steering-gear sector shaft that converts the gear's rotation into back-and-forth motion of the drag link.

An unwanted change in toe (wheels steer themselves) when the suspension moves over a bump — from worn parts or wrong ride height.

The truck wanting to keep turning the way it was last steered, usually from a binding ball joint, kingpin, or steering shaft.

Low fluid, weak pump, air in the system, worn gear, binding kingpins or linkage, low tire pressure, or a dry 5th-wheel plate.

Usually air trapped in the system — bleed/burp it and check fluid level. Often shows as foamy, aerated fluid in the reservoir.

Points to a fault in the steering-gear control valve, not the pump.

Insufficient positive caster, binding kingpins or column, a tight/dry gear, or low tire pressure.

A diagnostic that turns the steering wheel slightly while watching the linkage to feel which joint has free play or binds.

Universal joints in the steering column/shaft. Worn or binding joints cause free play, notchy steering, or poor return.

The on-center adjustment of the steering gear. Adjust only after linkage and mesh are good — over-adjusting binds the gear on center.

The hydraulic fluid for the assist system. Use the specified type; low or aerated fluid causes noise, hard steering, and pump wear.

The hydraulic cylinder that applies power assist to the steering linkage on a linkage-type system.

A shock-absorber-like damper on the steering linkage that controls shimmy and road shock. A worn damper allows wander or shimmy.

A pivoting joint allowing the suspension and steering to move. Worn ball joints cause looseness, noise, and unstable alignment.

The articulating end of a tie rod. A worn tie-rod end causes excessive toe change, free play, and rapid tire wear.

The ball-and-socket end of the drag link. Wear here adds free play and wander to the steering.

The pitman arm must be properly indexed/torqued to the sector shaft; looseness causes steering play and wander.

Limits maximum system pressure to protect components; a stuck or faulty relief valve can cause hard steering or noise at full lock.

Regulates fluid flow from the pump so assist stays consistent across engine speeds.

The full range of steering movement. Stops and steering-stop bolts limit cut to prevent tire-to-frame contact.

The truck drifts and requires constant correction. Caused by worn linkage, loose bearings, low caster, or a thrust-angle error.

A rapid side-to-side oscillation of the front wheels, from imbalance, worn parts, or a bad steering damper.

Drives the pump from the engine. A loose or glazed belt causes squeal and inconsistent assist (where belt-driven).

The casting that holds the wheel spindle and pivots on the kingpin (or ball joints) so the wheel can steer.

Worn kingpin bushings allow the knuckle to move, causing free play, shimmy, and unstable camber/caster.

The gear must be securely bolted to the frame. Loose mounting or cracked frame at the gear causes play and erratic steering.

Carries high-pressure fluid from pump to gear. A leaking or restricted hose causes assist loss, noise, and fluid loss.

Measuring the torque needed to turn the steering wheel to confirm correct assist; high effort indicates a hydraulic or binding fault.

Cycling the steering lock-to-lock (often with wheels raised) and topping up fluid to remove trapped air after a repair.

Internal wear adds lash and makes the gear loose on-center; causes free play and wander that adjustment can't fully fix.

Connects the steering wheel to the gear through the shaft and U-joints. Binding here hurts return and feel.

The arm on the knuckle that the drag link or tie rod attaches to; a bent steering arm changes turning radius and toe.

The truck's tie-rod cross tube connecting the two knuckles; bent or worn ends throw off toe and cause wander.

Low power-steering fluid causes hard steering, pump whine, and aerated fluid; check level and inspect for leaks first.

A heavy-truck assist arrangement using air pressure to boost hydraulic steering; diagnosed by checking both air supply and hydraulics.

Seals the gear's input shaft; a leak here loses fluid and can let air in, causing assist problems.

Limit wheel cut to prevent tire or linkage interference; set per spec after steering or alignment work.

A brake pulling to one side feels like a steering pull but is a brake fault (dragging caliper/shoe), not alignment.

Driving to confirm the complaint and note speed, braking, and road-crown effects before diagnosing steering or alignment.

Confirm and reproduce the complaint — pull, wander, hard steering, shimmy, bounce, or noise — before testing.

Using a pry bar to load joints and bushings while watching for movement to locate worn steering/suspension parts.

Aerated, foamy fluid means air is being drawn in — low fluid or a suction-side leak; bleed and repair the leak.

Sets the gear's tightest point on-center; over-tightening causes binding and poor return, too loose causes free play.

Grease zerk fittings on tie-rod and drag-link ends and kingpins per schedule; dry joints wear fast and bind.

Easier in one direction, harder in the other usually means a steering-gear control-valve or torsion-bar fault.

Excess play at the wheel beyond the manufacturer's spec indicates worn linkage, a worn gear, or loose bearings.

The plate-and-jaw coupling on the tractor that locks onto the trailer kingpin, carrying the trailer load and allowing it to pivot.

A rubber bellows filled with air that replaces a steel spring on an air-ride suspension. A leaking bag lowers that corner and leans the truck.

A tandem-axle design where a rigid equalizing beam pivots on a center saddle to share the load between two axles; common on heavy vocational trucks.

Senses ride height at the axle and adds or exhausts air from the air springs to hold the frame level as load changes.

Specified distance from a frame/axle reference to the ground. Must be set correctly before alignment, or the angles read wrong.

A hydraulic damper that controls spring or air-bag oscillation. Worn shocks let the truck keep bouncing, causing cupping and poor control.

A stack of curved steel leaves that supports the axle and carries the load. Sag or broken leaves change ride height and can shift the axle.

The bolt locating the leaf-spring stack on the axle. If it breaks, the axle can shift — causing a thrust-angle error and pull.

The jaws that grip the trailer kingpin. Worn jaws or excessive fore-and-aft play create an unsafe coupling — adjust or replace.

The truck's structural backbone. Twisting, cracks, or loose fasteners (often from overloading) misalign the axles and suspension.

Multi-leaf springs stack several leaves for load and damping; mono-leaf (tapered) springs use one variable-thickness leaf, often lighter.

The swinging link at one end of a leaf spring that allows the spring to change length as it flexes.

The frame bracket that anchors a leaf spring's fixed end; cracks or wear here cause axle shift and noise.

The bolts clamping the spring to the axle. Loose U-bolts let the axle shift and cause alignment and wear problems.

The pivoting beam between two springs on a tandem that equalizes load between the axles over uneven ground.

A rod that locates the axle fore-and-aft and controls pinion angle on heavy suspensions. Worn bushings cause axle movement and vibration.

A leaking air spring lowers that corner, leans the truck, and may cause low-air warnings; soap-test to find the leak.

Sets the wrong ride height (too high or low) on a corner/axle, throwing off alignment and ride; re-adjust to the spec dimension.

Removes moisture from the truck's air supply feeding the suspension and brakes; a failed dryer lets water foul valves and bags.

The arm connecting the axle to the height-control valve. A bent or disconnected linkage gives wrong ride height.

Bounce the corner or inspect for leaks; a corner that keeps oscillating or a wet shock body means a worn shock.

Excessive dip when braking points to worn shock absorbers (they control the load transfer), not the springs.

The pivot bushing in the beam's center saddle. Wear causes axle misalignment, tire wear, and clunk noise.

Bushings at the beam ends connecting to the axles; wear allows axle movement and uneven tandem loading.

A structural brace tying the two frame rails together; cracks or loose rivets reduce frame rigidity and cause flex.

Inspect frame rails and brackets for cracks, especially at holes and welds; stop-drill and repair per the manufacturer.

Heavy-truck frames use Grade-8 bolts or huck/rivet fasteners; replace with the correct grade — never downgrade frame hardware.

The 5th-wheel plate must be greased; a dry plate causes hard steering, chatter, and uneven plate wear.

Excessive kingpin-to-jaw play means worn jaws or pivot bushings; an unsafe coupling — adjust or replace the lock.

A movable 5th wheel that adjusts the kingpin position to distribute axle load; the locking plungers must fully engage.

The 5th wheel must be securely mounted to the frame; loose or cracked mounts are a serious safety defect.

A coupling that hooks a trailer's drawbar eye for towing; inspect for wear, cracks, and proper latch engagement.

A bar linking the two sides of an axle to resist body roll in turns; worn bushings or links cause clunk and lean.

Measure ride height side-to-side; a sagged or broken spring lowers that corner, changing alignment and causing wear.

Exceeding rated load sags springs, stresses the frame, overheats tires, and causes premature suspension and tire failure.

Exhausts air from the bags to lower the truck (e.g., for coupling/loading); must re-inflate to ride height before driving.

The beam that locates the axle and pivots at the front bushing on many air-ride suspensions; worn bushings cause axle shift.

Wrong ride height changes caster and pinion angle and skews alignment readings — always verify it before measuring angles.

The pad where the spring sits on the axle; a shifted or worn seat changes pinion angle and axle position.

Pry-check spring, beam, torque-rod, and sway-bar bushings for play; worn bushings cause noise, wander, and tire wear.

After a dump or service, the suspension must re-inflate to spec ride height before driving or aligning.

The bushing at a leaf spring's eye; wear allows axle movement and clunk and affects alignment.

An extra spring that engages under heavy load to add capacity; inspect for contact and wear at full load.

Soap-test bags, lines, and fittings to find a suspension air leak; a slow leak shows as a lean after parking.

The eyes and bushings mounting a shock; worn mounts let the shock clunk and reduce damping.

Measuring frame rails diagonally for 'diamond' (out-of-square) and checking for twist after a collision or overload.

Confirm the jaws fully close and lock around the trailer kingpin; a partial lock is a critical safety defect.

The 5th wheel pivots fore-and-aft (and sometimes side-to-side) to follow the road; worn pivot bushings add play.

Clunks over bumps point to worn bushings, U-bolts, shackles, or shocks; isolate by location during a road test.

A lean on air ride means a leaking bag or a stuck/misadjusted height-control valve — check ride height each corner.

A broken leaf lowers ride height, may shift the axle, and can cause a clunk and a pull on that side.

Worn torque (radius) rod bushings let the axle move fore-and-aft, causing vibration, pinion-angle change, and wear.

Worn stabilizer-bar links or bushings cause a rattle and increased body roll in turns.

The driveline angle set by axle position; a shifted axle or sagged spring changes it and causes driveline vibration.

Replace loose frame rivets with the correct grade fasteners per the maker; never use ordinary bolts on the frame.

Compare loaded and unloaded ride height; a corner that won't rise to spec indicates a weak spring or air-system fault.

Check bags for cracks, chafing, and proper inflation; a chafed bag against a frame member will fail early.

A dry plate scores and wears; it causes hard steering and chatter on turns — keep it greased and inspect the surface.

Each suspension has a published ride-height dimension; set it before alignment and after any spring or air-bag service.

The difference between the front and rear of a pair of tires viewed from above (toe-in or toe-out). Incorrect toe is the #1 cause of rapid, feathered front-tire wear.

Forward/rearward tilt of the steering axis viewed from the side. Positive caster aids straight-line stability and steering return.

Inward/outward tilt of the wheel viewed from the front. Excess camber wears one tire edge; unequal camber causes a pull.

The direction the rear (or tandem) axle actually points vs. the frame centerline. A non-zero thrust angle causes dog-tracking and tire wear.

Inward tilt of the kingpin/steering axis viewed from the front. Helps self-centering; not adjustable — a change means a bent part.

Ackermann geometry that makes the inner wheel turn sharper than the outer in a corner. An error means a bent steering arm.

When the rear axle doesn't follow directly behind the front because of a misaligned (non-square) axle, so the truck travels crab-wise.

Toe-in: fronts of the tires closer together; toe-out: fronts farther apart. Solid-axle trucks usually run a small toe-in.

Positive caster tilts the steering axis rearward at the top (stable, self-centering). Negative caster reduces return and stability.

A truck pulls toward the side with less (more negative) caster. Unequal caster is a common cause of a steady pull.

A truck pulls toward the side with more positive camber. Excess camber also wears one tire edge.

The sum of camber and SAI on a wheel; comparing side-to-side helps detect a bent spindle or knuckle.

The distance between the tire centerline and the steering-axis contact point. Set by SAI and camber; affects steering feel and wear.

When one wheel of an axle is farther back than the other (axle not square). Causes a pull and crooked steering wheel.

Squares the rear/tandem axle to the frame first, then sets front toe to the thrust line so the steering wheel is centered.

Both drive axles must be parallel and square to the frame; a shifted axle causes dog-tracking, pull, and tire wear.

A crooked steering wheel when driving straight usually means a thrust-angle error or toe set unevenly side-to-side.

Before aligning: correct tire pressure and matched tires, good linkage and bearings, correct ride height, and level equipment.

Set at the tie-rod sleeve/cross tube; center the steering wheel and set toe evenly on both sides, then road-test.

Camber on a solid axle is usually not adjustable; excess camber means a bent axle beam or spindle that must be corrected.

Where adjustable, caster is changed with shims or wedges between the spring and axle; otherwise a bent part is the cause.

SAI isn't adjustable, so an out-of-spec SAI (or unequal side-to-side) indicates a bent spindle, knuckle, or axle.

If the inner wheel doesn't turn sharper than the outer correctly, a steering arm is bent — replace it, don't adjust.

If a pull reverses when you swap front tires side-to-side, a tire (radial pull) is the cause, not alignment.

Road crown causes a slight steady drift right; a true alignment pull is stronger and consistent regardless of the road.

A saw-tooth edge you feel by running a hand across the tread is the signature of incorrect toe.

Wear on the inner or outer shoulder of a tire points to excessive camber (or a bent axle).

On a solid front axle, toe is typically the only routinely adjusted alignment angle.

Center the steering wheel before final toe so the wheel sits straight when the truck tracks straight.

Never align over worn linkage or bearings — toe won't hold. Replace worn ends and set bearings first.

The line bisecting rear-axle toe; the front wheels are aligned to it so the truck tracks straight with a centered wheel.

Too much positive camber wears the outer tire edge; too much negative wears the inner edge.

Caster mainly affects stability and return, not tire wear directly; a big caster error shows as poor return or pull.

Alignment must be done on a level rack with the equipment calibrated; an un-level surface skews every reading.

Compare side-to-side camber, SAI, and included angle; mismatches reveal a bent axle beam, spindle, or knuckle.

A low front tire increases rolling resistance on that side and pulls the truck toward it — check pressure first.

A rear/tandem axle not square to the frame (shifted spring, broken center bolt, worn bushing) makes the truck crab.

The two drive axles must be parallel to each other and square to the frame; check both during a thrust alignment.

Compare left and right camber; a side that's far off (with matching SAI off) usually means a bent axle or spindle.

If toe changes as the suspension moves (bump steer), suspect worn parts or incorrect ride height altering geometry.

Re-check alignment after replacing tie-rods, drag links, kingpins, springs, or shocks — geometry may have changed.

Check pressure, then tires (swap test), then brakes, then alignment angles — cheapest and most common causes first.

Verify the wheel returns to center and sits straight after setting toe; if not, re-center or recheck caster and thrust angle.

A bent spindle shows as abnormal camber and included angle on one wheel; replace the bent part rather than 'adjusting.'

The side-to-side difference in camber or caster; too much difference causes a pull and must be brought within spec.

Heavy trucks emphasize axle squareness, ride height, and toe on solid axles; many car-style camber/caster adjustments aren't present.

A series of dips around the tread caused by the tire bouncing — usually worn shocks, loose bearings, imbalance, or a bent rim.

A saw-tooth tread edge you can feel by hand, caused by incorrect toe scrubbing the tire sideways as it rolls.

The tapered roller bearing supporting the wheel on the spindle. Packed and adjusted to a small end play; over-tight bearings run hot and fail.

Out-of-roundness of a tire/wheel assembly that causes a speed-related vibration; corrected by truing, indexing, or replacement.

Distributing weight evenly around a tire/wheel assembly so it doesn't vibrate at speed; imbalance causes a shimmy that worsens with speed.

The paired rear tires on each side of a heavy axle. They must be matched in pressure and diameter, or the larger tire overloads and wears unevenly.

Inflation must match the actual axle load from the load/inflation table — not just the sidewall maximum.

Too little air lets the shoulders carry the load — both edges wear and the tire overheats.

Too much air makes the crown carry the load — the center of the tread wears.

Paired duals must match in pressure and diameter; a larger/harder tire overloads while the other scuffs, wearing the inner tires.

Mismatched or under-inflated inner duals carry the load unevenly and wear early — match pressure and diameter.

A bounce problem: worn shocks, loose/worn wheel bearings, imbalance, or a bent rim letting the tire hop.

A vibration that increases with road speed usually means imbalance, radial runout, or a bent rim — check the tire/wheel first.

Seat the bearing by torquing while rotating, back off, then re-torque to the light final spec to set a small end play.

The slight free movement of an adjusted tapered bearing (commonly about 0.001–0.005 in.); too tight runs hot, too loose wobbles.

A hub running hotter than its mates means over-tight or dry bearings, or a dragging brake — investigate before it seizes.

A sealed hub assembly torqued to a fixed spec instead of manually adjusted; replaced as a unit when worn.

Seals lubricant in the hub. A leaking seal lets oil onto the brake and bearing — replace the seal and clean the brake.

Some truck hubs run in an oil bath with a sight glass; others are grease-packed. Service to the correct lube and level.

Inspect rims for cracks, bent flanges, and elongated bolt holes; a damaged rim causes runout, vibration, and air loss.

Torque wheel fasteners to spec in the correct cross pattern; under- or over-torque causes loose wheels or broken studs.

Hub-piloted wheels center on the hub and use flanged nuts; stud-piloted center on the studs and use inner/outer caps. Don't mix.

Moving tires to even out wear; follow the truck's pattern and re-torque wheels after the specified mileage.

Radial tires have plies running across the tread for cooler running and better wear; don't mix radial and bias on an axle.

Static balance corrects up-and-down hop; dynamic balance corrects side-to-side wobble. Heavy trucks usually need both.

Side-to-side wobble of a tire/wheel assembly; excessive lateral runout causes a shimmy and must be corrected or replaced.

Federal limits require deeper tread on steer tires than on other axles; measure with a gauge and replace worn tires.

Steer tires show alignment problems first (feathered, one-edge, cupped) because they steer and carry front load.

Most truck wheel bearings are set to a slight end play, not pre-load; follow the spec — pre-loading runs them hot.

A tapered bearing has a cup (outer race) pressed in the hub and a cone (rollers); replace both as a matched set.

Retains and sets bearing adjustment; use the correct washer/lock and torque sequence so the setting can't change.

A dragging brake heats the hub and can wear or overheat the tire; it also mimics a steering pull.

A thrown balance weight causes a sudden vibration at the speed it was balanced for; re-balance the assembly.

A tire with radial runout thumps and vibrates at speed even when balanced; correct runout or replace.

Different rolling diameters on an axle (especially duals) scuff and wear tires and stress the drivetrain.

The chart that gives the correct cold inflation for a given axle load; the basis for setting truck tire pressure.

When replacing a wheel seal, inspect and repack or replace the bearings and set adjustment — don't reuse a damaged seal.

Steer tires should be matched and in good condition; a mismatched or worn steer tire causes pull and poor handling.

A growl or roar that changes with load or cornering points to a worn or improperly adjusted wheel bearing.

Feel or scan hub temperatures after a run; one hot hub warns of bearing or brake trouble before failure.

Re-torque wheel fasteners after the first miles of driving following any wheel-off service to catch seating and loosening.