Tools & consumables
- Floor jack and 2 properly rated jack stands (per side) + wheel chocks
- 1/2" drive breaker bar, 3/8" drive ratchet set, extensions
- Socket set including large axle nut socket (commonly 32–36 mm for Mazda3; check exact size for your year)
- Torque wrench (range to at least 200 ft·lb)
- Impact wrench (optional but speeds axle nut removal)
- Hex/Allen and Torx sockets if required
- Pry bar, flat screwdriver, pick
- Hammer and a punch (for cotter pins / hub drift)
- Ball joint separator or pickle fork (tie rod/end/ball joint separation)
- Hub puller or slide hammer with hub attachment (for pressed-on hubs)
- Hydraulic or mechanical bearing press or a set of bearing/driver cups (if replacing pressed-in bearing instead of whole hub)
- Wire brush, brake cleaner, rags
- Anti-seize compound and high-temp grease (if required)
- New axle nut (always replace), new cotter pin or locking device if applicable
- Replacement part: either complete wheel hub bearing assembly (recommended) or inner/outer wheel bearing kit + seals (depending on model/year)
- Thread locker (blue medium)
- Safety glasses, gloves

Safety precautions (read before starting)
- Work on a level surface. Chock opposing wheels. Never rely on the jack alone — always use jack stands positioned under factory jacking points or solid subframe.
- Wear eye protection and gloves. Keep hands clear when releasing suspension components.
- Disconnect battery if you’ll be handling ABS sensor wiring or using extensive electrical tools.
- Do not heat ABS tone rings or sensors; excessive heat damages them.
- Follow torque specs exactly and re-check after 100–200 miles.

Which method applies to your Mazda3
- Newer Mazda3 models (2010s onward, many BL/BM/BN) commonly use a bolt-on hub assembly (sealed hub bearing unit). Replace the whole hub — easiest and recommended.
- Older Mazda3 models or some variants may use pressed bearings in the knuckle — those require a press to remove/fit bearings or replacing the entire hub assembly if available.

Step-by-step — hub-assembly replacement (most common, quickest, recommended)
1. Preparation
- Loosen lug nuts slightly while car on ground.
- Loosen axle nut (if front axle passes through hub) while on ground with breaker bar/impact. If locked by cotter pin, remove pin first.
2. Raise & secure vehicle
- Jack car and place on stands under manufacturer jacking points. Remove wheel and tire.
- Chock contralateral wheels.
3. Remove brake components
- Remove caliper bolts and hang caliper with a hanger — do not let it hang on the brake hose.
- Remove brake rotor. On some models rotor slides off; others use a retaining screw.
4. Disconnect steering knuckle components
- Remove cotter pin / castle nut on tie rod end or lower ball joint as needed. Use ball joint separator to disconnect.
- Disconnect lower ball joint or strut-to-knuckle bolts depending on front suspension design to provide enough knuckle movement to extract the hub/axle.
- Disconnect ABS sensor and remove sensor harness clips so you can move the knuckle freely.
5. Remove axle from hub (if applicable)
- Remove axle nut (already loosened). Push axle shaft inward to free splines from hub. Use a punch on end of axle (light taps) or use pry if necessary; do not pull on axle joints excessively.
- If stubborn, use a hub puller or pry gently between hub and axle flange while supporting the transmission case. Beware of CV joint damage — if axle splines are stuck to hub, use a slide hammer on a hub puller from hub side.
6. Unbolt hub assembly
- Remove the hub-to-knuckle bolts (usually 3 or 4). Support hub as bolts are removed — it’s heavy.
- Remove hub assembly. If it’s seized due to corrosion, use penetrating oil, heat on knuckle (not on ABS ring/sensor), and a puller.
7. Install new hub assembly
- Clean mating surface on knuckle with wire brush — remove rust/paint buildup for proper seating.
- Apply a thin coat of anti-seize on the hub mounting surface if desired (don’t contaminate bearing faces).
- Fit new hub assembly in place, ensure ABS tone ring and sensor align correctly.
- Torque hub bolts to factory spec and use thread locker if specified.
8. Reassemble axle & brake components
- Slide axle into hub spline fully; ensure inner bearing seats properly (if slipping, check hub seating).
- Install new axle nut and torque to spec. Many Mazda3 require a high torque (example: 174–217 ft·lb depending on year); check manual. If a cotter pin is used, torque to spec, then back off to align cotter pin hole and install new pin.
- Reinstall rotor, caliper, wheel and lower car to ground slightly to preload wheel bearings per procedure if required.
- Torque lug nuts in star pattern to spec (usually 80–100 ft·lb for many Mazda, check spec).
9. Final checks
- Reconnect ABS sensor, ensure wiring routed correctly.
- Pump brake pedal if caliper was removed to restore pressure.
- Test-drive slowly and listen for noise; re-torque axle nut and lug nuts after 50–100 miles.

Step-by-step — pressed-in bearing replacement (if hub bearing is serviceable only by press)
1. Follow steps 1–5 above to remove knuckle/hub assembly from vehicle, or remove knuckle from vehicle if needed.
2. Remove hub/rotor assembly from knuckle and place on press bed.
3. Press out old bearing using a bearing press and correct driver cups. Use a driver that presses only on the outer race to avoid damaging knuckle. If removing inner race, press from opposite side with support.
- Important: support the knuckle so only the bearing is moving. Use correct-sized collars to avoid collapsing the bearing.
4. Clean knuckle bore thoroughly. Inspect for scoring or warpage — do not install new bearing into damaged bore.
5. Press new bearing in straight. Drive on the bearing outer race only. Do not apply force to the inner race when installing — that would damage bearing.
6. Reassemble hub/knuckle and follow steps 7–9 above.

How the specific tools are used (practical tips)
- Bearing/hub puller: attach jaws or hub adapter behind hub flange and tighten center bolt to pull hub outward. Use penetrating oil and heat if seized. Slide hammer can be used through hub to pull. Protect ABS ring.
- Bearing press: use a bench press or shop press with appropriate size drivers. Use a sacrificial sleeve or driver that contacts only the bearing outer race when pressing in. Press slowly and squarely.
- Torque wrench: set to correct spec and tighten bolts in recommended pattern (star or incremental). Always final-torque bolts at operating temperature if manual requires.
- Impact wrench: helpful to break stubborn axle/hub nuts, but always final torque with calibrated torque wrench.

Replacement parts & consumables
- Wheel hub / bearing assembly (OEM or quality aftermarket) — recommended to replace whole unit if available
- Axle nut (replace)
- New cotter pin / locking tab (if applicable)
- Brake hardware if corroded
- ABS sensor (only if damaged)
- Grease/seal if servicing bearings rather than replacing hub
- Thread locker (blue)
- Anti-seize

Common pitfalls & how to avoid them
- Reusing axle nut or cotter pin — always replace axle nut; use new cotter pin or locking device.
- Damaging ABS tone ring or sensor with hammer/heat — disconnect sensor, protect it, don’t overheat.
- Pressing bearing improperly — never press on inner race when installing outer race (or vice versa) — contact the proper race only.
- Not replacing the hub assembly when available — pressed bearings are time-consuming; whole hub swap is faster and often cheaper in labor.
- Under- or over-torquing axle nut or hub bolts — always use torque wrench and factory specs.
- Forgetting to torque-check after road test — retorque axle nut and lug nuts after 50–100 miles.
- Letting caliper hang on hose — use a hanger; don’t stress the brake hose.
- Splitting CV boot or damaging CV joint — support the steering knuckle when separating suspension joints and use proper separators.

Typical torque values (confirm for your year/model in service manual)
- Front axle nut (varies by year): ~174–217 ft·lb (check exact)
- Wheel lug nuts: ~80–100 ft·lb
- Hub-to-knuckle bolts: 70–100 ft·lb (varies)
- Caliper bracket bolts: 70–100 ft·lb
Always verify with the Mazda service manual for your model/year.

Post-replacement checks
- Spin wheel by hand for roughness or noises.
- Check ABS light — if on, inspect sensor and tone ring; clear codes if necessary.
- Road-test for vibrations/noise; re-inspect torque on axle nut and wheel nuts after 50–100 miles.

Done. Follow factory service manual for exact specs and model-specific steps.
rteeqp73

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Scope and assumptions
- Procedure assumes a Mazda3 with a manual transaxle that uses a shift drum/selector mechanism. Steps are generic to Mazda manual transmissions — always cross-check with the vehicle’s factory service manual (FSM) for model year‑specific diagrams, torque specs, clearances and part numbers.
- You will be removing and disassembling the transmission. Plan for 4–8 hours depending on experience and whether parts must be replaced.

Safety first
- Work on a flat, level surface. Use wheel chocks.
- Disconnect negative battery terminal.
- Support vehicle securely on jack stands (never rely on a jack alone). Use a two‑post lift if available.
- Use a transmission jack to support and lower the transmission. Don’t improvise.
- Wear safety glasses, gloves, and steel‑toe footwear. Keep rags and oil absorbent handy.
- Drain gear oil into a pan and dispose per local regulations. Avoid skin contact with used oil.

Tools and consumables
- Metric socket set (6–24 mm), deep and shallow.
- Torque wrench (0–200 Nm range).
- Combination wrenches.
- Transmission jack or floor jack + adapter.
- Floor creeper, jack stands.
- Screwdrivers, picks.
- Snap‑ring/circlip pliers (internal & external).
- Drift punches and soft‑face hammer.
- Punch set and roll‑pin punches.
- Bearing puller / 2‑ or 3‑jaw puller.
- Hydraulic press (or bench press) for bearings if needed.
- Dial indicator with magnetic base (for endplay/runout).
- Feeler gauges and vernier caliper / micrometer.
- Seal driver / bearing installer set.
- Clean lint‑free rags, brake cleaner or parts cleaner.
- Assembly lube or ATF for reassembly.
- New gearbox oil (use type specified in FSM).
- New gaskets/seals, RTV sealant (as specified).
- Replacement parts (see list below).
- Marker or paint pen to mark orientation.
- Threadlocker (medium strength) if FSM specifies.

Common replacement parts to have on hand
- Shift drum (selector drum) – if scored or worn.
- Shift forks and fork pads (wear surfaces).
- Shift fork bushes/bearings/sleeves.
- Detent ball(s), detent spring(s), detent plate.
- Roll pins / selector shaft pins / circlips.
- Case gaskets and seals (output shaft, input shaft, cover).
- Bearings (input/output/mainshaft bearings) if worn.
- Synchronizer rings (if damaged) — inspect while disassembled.
- Gear oil.

High‑level procedure (step‑by‑step)

1) Preparation and access
- Remove battery negative cable.
- Remove intake plumbing, undertray, driveshafts (CV axles): disconnect hub nuts, use pry or puller to remove CV shafts from trans if required.
- Jack and support transmission with a transmission jack (position adapter under trans).
- Support engine with an engine support bar or a jack with a wood block under oil pan if separating engine/transaxle.
- Remove starter, shift linkage, clutch slave cylinder (do not damage hydraulic line; secure out of the way), and any electrical connectors on the trans.
- Unbolt bellhousing from engine, lower transmission straight down on the trans jack.

Tools used: sockets/wrenches to remove bolts, pry bar to separate mating surfaces if stuck. Transmission jack keeps trans controlled while removing fasteners.

2) External teardown to access selector housing
- Place trans on a clean bench on a padded stand.
- Drain remaining oil and remove the inspection/cover plate(s) on selector housing. Mark cover orientation and bolt locations for reassembly.
- Photograph or label components for orientation — marker on mating faces helps.

Tools used: drain pan, socket set, camera/phone for photos.

3) Remove shift lever/selector inputs and cover
- Remove shift lever linkage and selector shaft as needed to clear access to selector drum.
- Remove bolts holding selector cover / top cover. Use screwdrivers or picks to lift cover; if gasketed, be prepared to replace.

Tools: snap‑ring pliers if there are circlips on selector shaft. Soft‑face hammer to tap cover gently loose.

4) Index and note drum/fork positions
- Before disassembly, rotate shift drum to a neutral position and mark each shift fork and drum groove position with a marker/paint. Take multiple photos with drum at several positions (e.g., 1st, 3rd, 5th) so you can reassemble in exactly the same relation.
- Secure any small parts (springs, balls, pins) into labeled trays.

Why: The shift drum is indexed; forks must re-engage their respective grooves exactly or shifting will bind.

5) Remove retaining components and extract shift drum
- Remove detent assembly (springs/balls/detent plate) carefully — they can project. Use small magnetic tray.
- Remove roll pins or bolts securing shift forks to the selector drum or cross shafts. Some Mazda trans may use a shaft for forks — pull pins out with appropriate roll‑pin punch.
- Carefully lift shift forks clear of drum grooves. Do not force or pry forks — they engage thrust washers or bushes. You may need to move forks to neutral positions.
- Slide the shift drum out of the housing along its axis. It might require rotating to align lobes.

Tools: roll‑pin punches and drift punches to push pins out; snap‑ring pliers for circlips; magnetic tray to catch small parts. Use a soft‑face hammer to gently tap the drum out if lightly stuck.

Pitfall: Forcing the drum can damage grooves and forks. Always ensure forks are clear of grooves before withdrawing.

6) Inspect components for wear and damage
- Visually inspect drum grooves for scoring, pitting, or flattened lobes. Use calipers/micrometer to check diameter and compare to FSM limits.
- Inspect shift fork contact faces and fork pads for excessive wear/gouges. Check for thin or missing fork pad material.
- Check fork bushes/bearings: excessive axial/radial play, ovality, or scoring means replacement.
- Inspect detent balls/springs and groove on drum for wear or deformation.
- Check related synchronizers, shafts, and bearings while open — damaged synchros or bearings will cause shifting issues even with a good drum.

Tools: calipers, micrometer, feeler gauges, dial indicator for runout, parts cleaner.

7) Decide and replace parts
- Replace shift drum if grooves are worn beyond FSM limits or if obvious scored/heavily worn surfaces exist.
- Replace shift forks/pads if contact surfaces are worn or forks are bent.
- Replace fork bushes and detent springs/balls as a matter of course if showing wear — inexpensive compared to rework.
- Replace roll pins and circlips (single‑use items). Replace gaskets/seals.
- If you must press bearings out: use press and correct sized bearing driver; do not press on races that transmit load to wrong part.

Pitfall: Reusing worn forks or bushes causes quick recurrence. Replace small cheap parts proactively.

8) Clean and prepare for reassembly
- Clean all parts with parts cleaner; dry with lint‑free rags.
- Lightly lubricate sliding surfaces with assembly lube or specified gear oil.
- Replace gaskets/seals on covers etc. Apply RTV where FSM indicates.

Tools: parts cleaner, rags, gasket scraper, seal driver.

9) Reinstall shift drum and forks with correct indexing
- Refer to marks/photos and set drum to neutral indexing. Slide drum carefully into place, ensuring forks engage in their grooves correctly.
- Reinstall roll pins/circlips using the correct size punch; ensure pins are fully seated.
- Reinstall detent springs/balls/detent plate; verify detent action by rotating drum and feeling positive detents.
- Reinstall selector cover with new gasket; torque bolts to FSM spec (use torque wrench).

How tools are used: use punch to drive roll pins flush; snap‑ring pliers to seat circlips; torque wrench for correct bolt torque; dial indicator if checking drum axial clearance or endplay — set magnetic base and indicator to measure lateral movement of drum when prying.

Common pitfall: Incorrect indexing — if forks are not fully seated in drum grooves, shifting will be inaccurate or trans will lock in gear. Verify that all forks move freely through full drum rotation and that gears engage smoothly.

10) Bench test selector operation
- With drum installed and cover on, rotate drum through full travel while operating shift linkage to confirm gears engage/disengage at the correct detents and there’s no binding.
- Check for excessive endplay with dial indicator; compare to FSM. If out of spec, inspect bushings and bearing surfaces.

11) Reinstall transmission to car
- Align transmission to engine using appropriate alignment tool for clutch (if clutch removed). Tighten bellhousing bolts to FSM torque.
- Reconnect shift linkage, clutch slave, starter, wiring, and driveshafts. Replace hub nut and torque to spec. Refill with fresh gear oil to the correct level/type.
- Bleed clutch hydraulic system if slave/line was disconnected.
- Lower vehicle, reconnect battery.

Tools: alignment tool for clutch, torque wrench for bellhousing and axle nut, funnel for gear oil.

12) Road test and final checks
- Start vehicle, cycle through gears with vehicle stationary to check feel. Ensure neutral is stable.
- Short road test: shift through all gears under light load, then heavier acceleration where safe. Listen for crunching, binding, or missed shifts.
- Recheck gear oil level and torque on visible fasteners after warmup.

Specific tool usage notes
- Snap‑ring pliers: Select internal/external type matching ring. Squeeze lightly and pull ring straight out of groove; avoid bending ring.
- Roll‑pin punches: Use a punch the diameter of the pin’s hole, support opposite side, and drive pin straight out to avoid damaging housing.
- Dial indicator: Mount magnetic base solidly. Zero the indicator on a reference surface, then rotate drum or move part to measure runout/endplay. Small readings matter — compare to FSM.
- Bearing press: Use a correctly sized driver that contacts the bearing outer race when pressing off a shaft or inner race when pressing into place. Press evenly and slowly to avoid cocking the bearing.

Common pitfalls & how to avoid them
- Not labeling parts/positions: Always photograph and mark orientation to avoid misassembly.
- Reusing worn small parts: Replace detent springs/balls, roll pins, fork pads, and seals routinely.
- Forcing parts: If drum won’t slide out/in, double‑check fork position and remove offending fasteners rather than forcing.
- Wrong lubricant or insufficient lubrication: Use FSM‑specified gear oil and apply assembly lube to sliding surfaces.
- Skipping bench test: Always cycle the drum and linkage on the bench before reinstalling.
- Not torquing bolts to spec: Use torque wrench for bellhousing, cover, and axle nuts to avoid leaks or bolt failure.
- Contaminating parts: Keep parts clean; don’t allow shavings/metal debris to enter gearbox.

When to replace the drum vs. repair
- Replace drum if grooves are cut, pitted, or lobes are severely rounded — grinding/polishing is temporary and not recommended except by machine shop per FSM tolerances.
- Minor surface rust can be cleaned with fine emery/Scotch‑Brite and lubricated, but visible material loss requires replacement.
- Forks with slight pad wear can sometimes be serviced by replacing pads/bushings, but bent forks or heavy wear require replacement.

Final reminders
- Always use the FSM for torque specs, clearance tolerances and part numbers.
- Keep a clean organized workspace and a parts tray for small items.
- If uncertain about bearing replacement or pressing operations, use a shop press or a machine shop to avoid damage.

This is the full technician workflow for shift drum repair on a Mazda3. Follow the FSM for specs and replace any worn parts rather than attempting temporary fixes.
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