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Toyota 2H and 12H-T digital engine factory workshop and repair manual

Summary (what this is): This guide shows you how to replace the planetary gear set in the starter motor used on Toyota 2H / 12H‑T diesel engines. It explains why the repair is needed, how the starter’s reduction-gear system works, what parts you’ll touch, how to take the starter off the engine, how to disassemble the starter, how to replace and inspect parts, how to reassemble and test, and common failure modes and mistakes. It’s written for a beginner mechanic; read safety notes and go slowly.

Safety and prep
- Work in a well-ventilated, well-lit area on level ground. Use jack stands if you must get under the vehicle. Never rely on a jack alone.
- Disconnect the negative battery cable before touching the starter or electrical connectors.
- Wear eye protection and gloves. Keep loose clothing and jewelry away from moving parts.
- Have a clean bench, container for small parts, and camera or phone to take photos during disassembly for reference.

Tools and consumables
- Basic hand tools: metric sockets and ratchet, extensions, wrenches, screwdrivers (Phillips & flat), pliers.
- Snap‑ring (circlip) pliers (internal & external if available).
- Torque wrench (recommended for re-install).
- Small punch and hammer (for gentle taps).
- Cleaning solvent (electrical parts cleaner).
- Soft brush, lint‑free rags.
- High‑temperature, non-conductive grease (moly or lithium-based designed for gear/roller bearings) — small amount.
- Replacement planetary gear set (specific starter model part), replacement one-way clutch if required, new circlips, any worn bearings or thrust washers.
- Thread locker (blue) for certain bolts if manufacturer suggests.
- Multimeter for basic continuity checks and bench testing.

Theory: why a planetary reduction starter and why it fails
- Electric starter motors spin very fast but produce low torque. A planetary gear reduction takes the fast, low-torque rotation of the motor and converts it to slower, higher-torque rotation of the pinion that cranks the engine. Think of it like a multi-gear bicycle hub: the motor is the pedaling speed, the planetary set is the internal gearing that gives you more “push” at the wheel.
- Main components: sun gear (center), planet gears (several small gears on pins), planet carrier (holds planets), ring gear (internal-tooth gear in housing), pinion (output gear that engages the flywheel), and a one‑way (overrunning) clutch that allows the motor to drive the engine but prevents the engine from back‑driving the motor.
- Why replace the planetary set: worn/damaged teeth, chipped planets or sun gear, broken bearings, or failure of the one‑way clutch cause slow cranking, grinding noise, pinion not spinning, or starter free‑spinning with no engagement. Oil, dirt, or lack of lubrication and heavy loads can accelerate wear.

What can go wrong (symptoms and causes)
- Grinding when engaging: worn or missing teeth, damaged pinion or ring.
- Starter spins but engine doesn’t crank: slipped/damaged one‑way clutch, broken carrier, or missing/failed pinion engagement.
- Slow cranking: worn gears, bad bearings, weak brushes or armature issues.
- Noisy starter: loose components, worn bearings, or foreign debris.
- Starter sometimes works: intermittent electrical connection (solenoid contacts, battery cable), or worn one‑way clutch engagement.

High-level parts description (every component you’ll see)
- Starter housing / main body: outer shell that holds field coils or permanent magnets and supports other components.
- End caps (nose/drive end and commutator end): covers that hold bearings and keep components in place.
- Armature (rotor): the rotating core with commutator and shaft.
- Commutator: copper segments the brushes contact to feed current to armature.
- Brushes and brush holder assembly: carbon contacts that transfer current to the commutator.
- Field coils or permanent magnet assembly: creates magnetic field for the armature to rotate.
- Solenoid (starter solenoid): moves the pinion into mesh (on many designs) and closes the motor power circuit (on some setups, solenoid is separate).
- Pinion gear (small output gear): engages engine flywheel/flexplate.
- One‑way clutch/overrunning clutch (bendix style or sprag style): lets motor drive pinion but freewheels once engine starts.
- Planetary gear set: sun gear (center), planet gears (3+ small gears), planet carrier (holds them), ring gear (internal ring, sometimes integral with the nose/drive housing), circlips and thrust washers, bearings/bushings.

Step‑by‑step procedure

1) Remove the starter from the vehicle
- Safety: disconnect the negative battery terminal.
- Locate starter (usually lower on the bellhousing). Remove any heat shields or obstacles.
- Disconnect the large battery cable (positive) and the smaller solenoid control wire. Label or photo wires for reassembly.
- Unbolt starter mounting bolts (usually 2 or 3). Support weight of starter; remove and place on bench.

2) Inspect the starter as removed
- Note oil or grime on the outer housing (could indicate engine oil leak into starter area).
- Try to turn the pinion by hand (if accessible) to see if it turns freely and to hear grinding. Check approximate freedom.

3) Prepare to disassemble on the bench
- Clean exterior with a brush and solvent to reduce dirt entering during disassembly.
- Photograph orientations and wiring for reference.

4) Disassemble starter (typical reduction starter layout)
- Remove solenoid if it’s mounted to the starter body. Some starters have the solenoid accessible via small bolts; remove carefully and set aside.
- Remove end cap bolts (commutator/end plate) and separate the rear end plate. Be careful: springs on brushes may push the assembly as you open it. Remove the brush springs and brushes gently — remember their orientation and order.
- Slide out the armature: hold the starter with the nose pointing toward you and gently pull the armature straight out of the housing. Inspect commutator for heavy wear or scoring.
- Remove the front (drive) housing or nose cone to access the reduction gearset. Some designs are bolted with screws through the housing; others have circlips holding the nose. Remove any retaining bolts and carefully separate nose from the main housing.
- Once the nose is off, you will see the pinion assembly and the planetary gear assembly. There may be a big circlip or retaining ring securing the planetary carrier to the armature shaft — use circlip pliers to remove it.
- Remove the planetary carrier and planet gears. Note the exact stack order: thrust washers/spacers, planets, sun gear position, and any bearings/bushes.
- Remove the one‑way clutch or overrunning clutch assembly (may slide off the shaft). Note direction (which way it allows rotation) — often marked with an arrow.

5) Inspect all parts
- Planet gears and sun gear: check for pitting, chipped teeth, heavy wear, blackened/flattened surfaces. Light wear is normal; any broken or missing teeth means replace.
- Ring gear: inspect internal teeth for rounding or wear.
- Bearings/bushings: check for play, scoring, or seizure. Replace if rough or loose.
- Thrust washers and spacers: check for wear or deformation—replace if thin or scored.
- One‑way clutch: test freewheeling action. It should rotate freely one way and lock the other. If it slips or is rough, replace.
- Armature: check commutator for deep grooves, burnt areas. Check for shaft run-out or bearing damage.
- Brushes: measure remaining carbon length. Replace if short or if springs appear weak.
- Solenoid: check plunger movement and contact surfaces. Replace if contacts are burned or pitted.

6) Replace parts and prepare for reassembly
- Install new planetary gear set and clutch assembly if you purchased a kit. Compare old vs new to confirm proper orientation.
- Clean grease and old debris from housing and pinion area. Lightly lubricate gear teeth and bearings with small amount of high-temperature gear grease. Don’t overdo it — too much grease can fling onto the commutator and cause electrical problems.
- Replace any worn bearings, washers, and circlips.

7) Reassemble planetary reduction unit
- Reinstall planet gears into the carrier with their pins and any circlips.
- Fit sun gear and planet carrier back onto the armature shaft in the original order, ensuring thrust washers and spacers are in place.
- Reinstall the retaining circlip that holds the carrier. Ensure it is fully seated.
- Fit the one‑way clutch in the correct direction (arrow points toward the engine normally — verify on the new part or by how the pinion should drive the flywheel when starter power is applied).

8) Reassemble starter
- Reinstall nose/drive housing, align bolt holes and tighten evenly.
- Slide armature back into housing carefully, taking care not to damage brushes or the commutator.
- Reinstall brushes and springs into the brush holder; make sure each brush moves freely in its holder.
- Reinstall the rear end plate and tighten bolts snugly.
- Reinstall the solenoid and connect any linkages. Ensure the pinion throw-out (if used) and solenoid mechanical linkage operate freely.

9) Bench testing (basic)
- Reconnect the large battery cable to the starter just for a quick test bench spin: clamp the starter in a vice (soft jaws or rags so you don’t damage housing), connect the negative battery to the starter housing, then briefly touch the positive battery to the solenoid terminal to engage the motor. The pinion should spin and the one‑way clutch must lock in cranking direction; do very short bursts only. If you have a dedicated starter bench tester, use it.
- Listen for smooth operation, no grinding, and verify pinion extends and retracts if operated by the solenoid. Beware sparks—some sparking is normal, but heavy sparking means electrical issues.

10) Reinstall starter to engine
- Refit starter to engine bellhousing; hand‑start mounting bolts, then torque to OEM spec (if you don’t have exact torque values: snug and firm — usually 25–45 Nm for many starters — but consult a service manual for exact).
- Reconnect battery and control wires. Ensure good clean contact on battery cable clamps.
- Start engine to confirm operation. Listen for abnormal noises. Recheck mounting bolts after a short run.

Common mistakes and troubleshooting tips
- Not disconnecting battery before starting — risk of short/corroded contact sparks.
- Losing or misplacing small parts like circlips and pinion spacers — use a parts tray and camera.
- Over‑lubricating gear area — too much grease contaminates the commutator.
- Reinstalling one‑way clutch the wrong way — starter will spin but won’t crank engine.
- Not replacing worn bearings or washers — leads to premature re-failure.
- Mixing parts from different starter models — planetary sizes differ.
- Re-using brittle or fatigued circlips — always fit a fresh circlip if the old one is deformed.
- Not testing on bench — you might reinstall and find the starter still bad.

Parts to consider replacing at the same time
- Planetary gear set (sun, planets, carrier)
- One‑way overrunning clutch
- Pinion gear (if worn)
- Bearings/bushings and thrust washers
- Brushes and springs
- Solenoid (if contacts look pitted)
- Small parts kit (circlips, springs, seals)

Difficulty and time
- Difficulty: moderate. You don’t need specialized training, but careful hand tools skill and patience are required.
- Time: 1–3 hours bench time depending on experience and whether you’re replacing bearings/brushes. Allow more time if you need to source parts.

Closing analogy and final tips
- Think of the starter planetary set like a tiny, sealed solar system (sun gear in the middle, planet gears orbiting, and an outer ring fence). If one planet loses teeth or its axle wears, the whole system can’t deliver the torque to turn the engine. Replace the worn “planets” and clean the “space” to restore smooth balance.
- Keep parts organized and photographed. If you’re unsure of torque specs, consult the Toyota service manual for the exact starter model. Replace rather than jury‑rig worn parts; cheap fixes often fail quickly.
- If, after reassembly, the starter still shows electrical problems (weak spin, heavy sparking), consider checking battery voltage, battery cables, starter solenoid contacts, and armature/field coil continuity — electrical faults are often mistaken for mechanical faults.

No-yapping summary: disconnect battery, remove starter, disassemble on bench, remove and inspect planetary gear/set and one‑way clutch, replace worn gears/bearings/brushes, lightly grease, reassemble in original order, bench test, reinstall, retest. Follow safety, take pictures, and replace whole kit parts when in doubt.
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