Isuzu NPR NQR NPS NKR NHR N SERIES TRUCK Workshop Manual Digital Download

Tools & consumables
- Vehicle hoist or heavy-duty floor jack + heavy-duty jackstands (rated for truck weight)
- Engine support bar or engine hoist (to support engine when trans removed)
- Transmission jack (or second heavy-duty jack with adapter/wood)
- Metric & SAE socket sets, extensions, breaker bars
- Torque wrench (range to at least 150 ft·lb)
- Impact gun (use carefully) or long breaker bar
- Screwdrivers, pry bars, seal puller
- Transmission fluid drain pan, funnel, fluid transfer pump
- Shop rags, solvent, gasket scraper
- New torque converter (OEM or specified replacement)
- New torque converter-to-flexplate bolts (recommended), flexplate bolts if disturbed
- New transmission pan gasket and filter (recommended)
- New front pump seal / input shaft seal if warned by service manual
- Thread locker (blue medium strength) if specified by manufacturer
- Safety glasses, nitrile gloves, wheel chocks
- Penetrating oil, anti-seize (for bolts as required)

Safety precautions
- Work on firm level surface or use a commercial hoist. Never rely solely on a jack; use rated jackstands.
- Chock wheels and disconnect negative battery terminal.
- Support the engine before removing the transmission — transmission often supports engine weight on these trucks.
- Use a transmission jack to control weight and orientation; transmission is heavy and awkward.
- Keep hands and clothes clear when lowering or raising heavy components.
- Dispose of ATF properly; hot fluid can burn — allow to cool before draining.

Overview of the procedure (high level)
1. Prep vehicle and drain fluid.
2. Remove driveline/exhaust/starter/shifter linkages, wiring, mounts and crossmembers blocking transmission removal.
3. Support engine, separate bellhousing from engine and carefully lower transmission away from engine, taking care to remove torque converter-to-flexplate bolts through the bellhousing or after slight separation as applicable.
4. Remove old torque converter and install new one (with correct sealing, bolts and correct seating).
5. Reinstall transmission, torque bolts to spec, refill fluid and test.

Step-by-step procedure
1. Preparation
- Park, chock wheels, disconnect battery negative.
- Raise vehicle on hoist or use heavy jack + jackstands under frame. Ensure truck is secure. Use hoist for safest work.
- If available, consult Isuzu workshop manual for your exact model/year transmission and torque specs.

2. Drain automatic transmission fluid
- Place drain pan under transmission.
- Remove drain plug if fitted, or loosen pan bolts to drain. Removing pan is recommended (replace filter & gasket).
- Allow fluid to drain and clean mating surfaces when pan is off.

3. Remove external components
- Remove driveshaft (mark alignment), exhaust sections and heat shields that obstruct transmission removal.
- Remove starter motor to expose bellhousing bolts.
- Disconnect shift linkages, electrical connectors to the transmission, speedometer cable/sensor, cooler lines (cap lines to prevent contamination), and any vacuum lines.
- Remove transmission mount(s), crossmember(s) and any braces. Support the transmission with transmission jack.

4. Support the engine
- Use an engine support bar or engine hoist to prevent engine droop when transmission comes out. Do NOT rely on oil pan as support.
- Place a block of wood between jack and oil pan if using floor jack as temporary support — still use an engine support if possible.

5. Separate bellhousing
- With transmission jack supporting the weight, remove bellhousing bolts. Keep bolts organized by length/location.
- Carefully pry the transmission rearwards a small amount until the torque converter is accessible through the bellhousing inspection holes or until enough clearance to access converter bolts is achieved.

6. Remove torque converter-to-flexplate bolts
- Rotate the crank (or spin the torque converter by hand) to align access holes and bolt holes.
- Remove the converter-to-flexplate bolts (usually 3–6 bolts depending on design). These are often recessed; use an extension and locking device if needed.
- Common pitfall: not supporting transmission while removing these bolts — when bolts are removed the converter may fall out of the transmission input shaft area. Keep the transmission jack in place and slightly support the torque converter.

7. Separate transmission from engine
- Once converter bolts removed, slowly lower transmission back on the jack while ensuring the converter disengages from the flexplate and engine without contacting the crank or sealing surfaces heavily.
- Lower the transmission enough to clear the engine block and tip/rotate to allow removal. Be careful of fluid sloshing and wiring harnesses.

8. Remove torque converter from trans input shaft
- With the transmission on the jack, slide the torque converter off the input shaft. Inspect splines and input hub. If the torque converter is being replaced, install the new unit at this stage.
- Inspect front pump lip seal and input shaft for scoring. Replace seals/pump seal if damaged or per preventive maintenance.

9. Prep new torque converter & seals
- Fill the new torque converter with the specified ATF amount and rotate to distribute fluid into the converter (reduces dry-start risk).
- Replace any seals (front pump/input) and transmission pan filter and gasket while transmission is accessible.
- Replace any bolts that are specified as one-time-use (service manual will tell you). It’s recommended to use new converter-to-flexplate bolts.

10. Install new torque converter onto input shaft
- Carefully slide the torque converter onto the transmission input shaft. You must feel multiple positive engagements:
a) spline engagement to input shaft (rotate slightly while pushing)
b) then seating into the pump (you’ll feel a distinct seated position when it fully engages). Often you’ll hear/feel 2–3 “clicks” as it engages fully.
- Important pitfall: if the torque converter is not fully seated into the pump, you will not be able to bolt the transmission to the engine properly and you may damage the pump seal. Always confirm fully seated (measure/mark or count engagements per manual).

11. Reinstall transmission to engine
- With transmission jack aligned, raise transmission to the engine. Carefully align bellhousing to dowel pins and engage fully. You may need to rotate the crank slightly to align bolts.
- Install bellhousing bolts finger-tight, then torque to specification in the workshop manual in a cross pattern.

12. Reattach torque converter to flexplate
- Rotate the engine or converter to align bolt holes, insert new converter-to-flexplate bolts, tighten in a star pattern progressively to specified torque.
- Typical practice: tighten bolts in stages (finger-tight → snug → specified torque). Use blue Loctite only if specified.

13. Reassemble everything removed
- Reinstall starter, crossmembers, mounts, driveshaft (align marks), exhaust, wiring, shifter linkage and lines.
- Reconnect cooler lines and ensure clamps are secure; bleed air if necessary.

14. Refill transmission fluid
- Refill with manufacturer-specified ATF type and capacity. Start by adding partial amount, start engine (in park) and run to normal temp, cycle through gears, add fluid to proper dipstick level/hot measurement per manual.
- Check for leaks after running and after a short test drive.

15. Final checks
- Road test for proper engagement, check for noises, leaks and correct fluid level after warm-up.
- Re-torque bolts to spec after a short service interval if recommended.

How each tool is used (brief)
- Hoist/jacks/jackstands: lift and secure the vehicle at rated points.
- Engine support/hoist: holds engine weight when transmission is removed.
- Transmission jack: supports and aligns heavy transmission for safe removal/installation; use straps to secure.
- Torque wrench: final-torque fasteners to manufacturer specs. Always use proper range and calibration.
- Pry bar/seal puller: gently separate bellhousing mating surfaces or remove seals; avoid gouging mating faces.
- Socket set & impact: break loose and re-tighten bolts. Use impact carefully on critical bolts; finish with torque wrench.
- Drain pan/fluid pump: catch old ATF and refill new ATF cleanly.

Common pitfalls & how to avoid them
- Not seating torque converter fully into pump: results in input pump seal damage or inability to bolt trans to engine. Avoid by filling converter, rotating while sliding in, confirming full seating.
- Dropping heavy components: always use proper jacks and stands; secure transmission to jack with strap.
- Reusing old bolts that are torque-to-yield: always replace bolts specified as single-use.
- Damaging the front pump seal when installing converter: rotate slightly and use alignment, do not pry harshly.
- Cross-threading bolts: start bolts by hand and ensure alignment before torquing.
- Incorrect ATF type/level: will cause shifting problems or damage; use exact Isuzu specified fluid.
- Forgetting to support engine: engine movement can break mounts or wiring.
- Skipping filter/pan gasket: leaves contaminants in trans; replace filter/gasket when trans is separated.

Replacement parts typically required / recommended
- Torque converter (new unit)
- Converter-to-flexplate bolts (new)
- Flexplate bolts if removed / if specified as single-use
- Transmission pan gasket and filter
- Transmission fluid (correct grade & quantity)
- Front pump seal / input shaft seal (if worn or per manual)
- Transmission mount bushings, crossmember hardware (if corroded)
- Thread locker per OEM spec for specific bolts

Torque specifications
- Exact torque specs vary by engine/transmission and year. Always verify with the Isuzu workshop manual for your model/year. Typical ballpark examples (verify with OEM):
- Torque converter-to-flexplate bolts: roughly 30–50 ft·lb (40–70 N·m)
- Flexplate-to-crank bolts: roughly 65–95 ft·lb (90–130 N·m)
- Bellhousing bolts: roughly 50–85 ft·lb (70–115 N·m)
- DO NOT rely on these ballpark numbers for final assembly — use the Isuzu manual.

Final note
- Follow the Isuzu service manual for model/year-specific details (bolt counts, torque specs, seal part numbers, fluid type). Replacing the torque converter is heavy, takes time and requires proper support and torque controls. If unsure at any step, consult a qualified transmission technician.
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Isuzu N Series Walkaround By Jazmine Keith, Sales Representative, Boyer Trucks Boyer Trucks Isuzu Sales Representative Jazmine Keith does an in-depth walkaround of an Isuzu N-Series Truck. She highlights ...

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