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ISUZU NPR 4BC2 Crankshaft 5123101612 5-12310161-DG OEM Fit
Crankshaft 5123101612 5-12310161-DG for ISUZU NPR 4BC2 Diesel Engine — Verified OEM Fit for 3.3L 4-Cylinder Crankshaft Assembly
The Crankshaft with OEM numbers 5123101612 and 5-12310161-DG is a verified direct-fit replacement for ISUZU NPR trucks equipped with the 4BC2 3.3L diesel engine. This crankshaft is the core rotating component of the engine, responsible for converting the linear reciprocating motion of the pistons and connecting rods into rotational torque that drives the vehicle's drivetrain and accessories.
Working Principle
The crankshaft is the most critical component in the engine's power conversion process. It receives force from the connecting rods and converts it into torque, which is transmitted through the crankshaft to drive the vehicle and operate engine accessories. The crankshaft must have sufficient strength and rigidity, and its journal surfaces must be wear-resistant, uniform, and balanced. The 4BC2 engine is known for its robust internal components — with basic maintenance, these engines commonly exceed 500,000 miles (800,000+ km), and the crankshaft is a key contributor to this durability.
Failure Symptoms
Replace the crankshaft when any of these symptoms appear:
Heavy knocking noise from the bottom end of the engine — worn main bearings or connecting rod bearings allow excessive crankshaft movement.
Abnormal engine vibration — imbalance, wear, or scoring on the crankshaft journals causes vibration throughout the engine operating range.
Low oil pressure — worn crankshaft journals increase bearing clearance, reducing oil pressure and triggering the warning light.
Metal debris in the oil pan — bearing material particles indicate crankshaft journal wear or scoring.
Engine seizing or inability to rotate — severe bearing failure or thrust bearing wear can seize the crankshaft.
Critical Inspection Note: ISUZU service manuals require that the crankshaft be inspected for journal roundness, taper, and surface finish during any engine overhaul. If journals are out of specification, the crankshaft must be replaced or reground to undersize dimensions with matching bearings.
Technical Specifications
Verification Item
Data / Standard
Source / Method
Part Number (Short)
5123101612
ISUZU OEM Parts Database
Factory Number
5-12310161-DG
ISUZU OEM Parts Database
Part Name
Crankshaft
ISUZU EPC
Engine Compatibility
4BC2 (3.3L, 4-cylinder, OHV, DI)
ISUZU application catalog
Vehicle Models
ISUZU NPR / NKR / KT / TLD
ISUZU application catalog
Eccentric Diameter
50 mm
Gasgoo crankshaft specification table
Main Journal Diameter
70 mm
Gasgoo crankshaft specification table
Connecting Rod Journal Diameter
64 mm
Gasgoo crankshaft specification table
Overall Length
647 mm
Gasgoo crankshaft specification table
Net Weight
28.1 kg
Product specification
Material
Alloy Steel
Material certificate
Package Size
72 * 21.5 * 18 cm
Product specification
Crankshaft Bearing Cap Bolt Torque
225.4–245.0 N·m
ISUZU 4BC2 workshop manual
Connecting Rod Bearing Bolt Torque
78.4–88.2 N·m
ISUZU 4BC2 workshop manual
Warranty
6 Months
Manufacturer standard
Certification
ISO/TS 16949
Third-party system audit
OEM Cross-Reference
Type
Number
Primary OEM — Short
5123101612
Factory Number
5-12310161-DG
Alternate Format
5-12310161-0
Alternate Format
5-12310-161-0
Alternate Format
5123101610
Related Crankshaft — 4BD1
5123101630
Related Crankshaft — 4BE1
8944163732
Vehicle & Engine Compatibility
Primary Applications
Brand
Model
Chassis
Engine
Years
ISUZU
ELF
NKR
4BC1 / 4BC2
1982–1987
ISUZU
NPR
NPR
4BC2
1982–1987
ISUZU
NPR
NPR
4BC1 / 4BC2 / DB33
1985–2024
ISUZU
KT
KT
4BC2
1982–1987
ISUZU
TLD
TLD
4BC2
1982–1987
Important Fitment Notes:
The 4BC2 crankshaft is a forged or cast alloy steel component. Verify the crankshaft journal dimensions against the old unit before ordering.
The 4BC2 engine was sold in ISUZU ELF and NPR trucks from 1982 to 1987, and continued in various applications through 2024. Confirm your specific engine model and year.
For engines that have been previously reground, verify the current journal diameter before ordering a standard-size crankshaft.
Fitment Verification: To ensure 100% accurate matching, please provide the VIN or chassis number before ordering. We will verify it through the ISUZU global EPC system.
Features & Benefits
Feature
Benefit + Verification Signal
Alloy Steel Construction
High tensile strength and fatigue resistance for reliable power transmission — verified by material certificate and hardness testing.
Precision Journal Machining
Uniform journal surfaces ensure proper bearing clearance and oil film formation — verified by CMM dimensional inspection.
4BC2-Specific Dimensions (50/70/64/647 mm)
Direct drop-in fit for ISUZU NPR 4BC2 engines without modification — verified against Gasgoo crankshaft specification table.
Dynamic Balancing
Reduces vibration and abnormal wear, extending engine life — verified by dynamic balancing equipment.
Heat Treatment
Surface hardening for wear resistance on journals — verified by hardness testing.
ISO/TS 16949 Quality System
Full traceability with material certificates and batch inspection reports — third-party certified.
Quality Control & Verification
QC Item
Verification Method / Standard
Journal Diameters (Eccentric / Main / Rod)
CMM, 100% inspection
Overall Length
CMM, 100% inspection
Journal Roundness & Taper
Roundness tester, 100% inspection
Surface Hardness
Rockwell hardness tester, batch sampling
Dynamic Balance
Dynamic balancing machine, 100% inspection
Material Composition
Spectrometer analysis, batch sampling
Surface Finish (Ra)
Surface roughness tester, 100% inspection
Crack Detection
Magnetic particle inspection (MT), 100% inspection
Keyway Dimensions
CMM, 100% inspection
Thread Inspection (Flywheel / Pulley)
Thread gauge, 100% inspection
Batch Traceability
Material lot number + production date
Packaging Protection
Anti-rust oil + VCI film + wooden case
Installation & Maintenance Recommendations
IMPORTANT: Crankshaft installation is an engine overhaul-level operation. It must be performed by a qualified diesel engine technician in a clean workshop. All bearing clearances must be measured with Plastigauge or micrometer before final assembly.
Preparation: Remove the engine from the vehicle. Disassemble the engine and remove the old crankshaft. Clean the cylinder block main bearing bores thoroughly.
Bearing Installation: Install new main bearings into the cylinder block and bearing caps. Apply clean engine oil to all bearing surfaces.
Crankshaft Installation: Carefully lower the crankshaft into the block. Install the bearing caps in their original positions with the arrows facing the correct direction.
Torque Sequence: Tighten the crankshaft bearing cap bolts to 225.4–245.0 N·m in the numerical order specified in the workshop manual, a little at a time in stages.
Connecting Rod Installation: Install the connecting rods and pistons. Tighten the connecting rod bearing bolts to 78.4–88.2 N·m.
End Play Check: Measure crankshaft end play with a dial indicator. Ensure it is within the workshop manual specification.
Rotation Check: Rotate the crankshaft by hand to verify smooth rotation without binding.
Final Assembly: Install the flywheel, pulley, and other accessories. Torque all fasteners to specification.
Recommended Torque Values:
Fastener
Torque
Crankshaft Bearing Cap Bolts
225.4–245.0 N·m
Connecting Rod Bearing Bolts
78.4–88.2 N·m
Maintenance Schedule
Every 5,000–10,000 km: Change engine oil and filter. Check oil pressure.
Every 40,000–50,000 km: Perform oil analysis to detect bearing wear metals.
At engine overhaul: Inspect crankshaft journals for wear, scoring, or cracks. Replace if out of specification.
Whenever bearing failure occurs: Replace the crankshaft if journals are damaged or out of round.
Packaging & Supply
Standard Packaging: Anti-rust oil + VCI film + wooden case.
Yimi (Guangzhou) Automotive Parts Co., Ltd.
Located in Guangzhou—the economic and transportation hub of Southern China—we are a specialized supplier and exporter with over 20 years of experience in the automotive parts industry. We focus on the production and sales of high-quality ... Yimi (Guangzhou) Automotive Parts Co., Ltd.
Located in Guangzhou—the economic and transportation hub of Southern China—we are a specialized supplier and exporter with over 20 years of experience in the automotive parts industry. We focus on the production and sales of high-quality ...
