3LM-373 Turbocharger For Caterpillar 3306 / 3306B Diesel Engine | 7N-7748 Or 8N-9247 Configuration

A 3LM-373 marking identifies the turbo family, but it does not by itself confirm the correct assembly. For Caterpillar 3306 service work, buyers should compare the engine number, machine model and identification stamped on the original turbocharger. This matters because two frequently searched versions-7N-7748 and 8N-9247-are associated with the 3LM-373 family but follow different interchange routes. They should not be treated as automatic substitutes.

The 3LM-373 is an exhaust-driven turbocharger developed for heavy-duty Caterpillar diesel applications. Exhaust energy rotates the turbine wheel, while the connected compressor increases intake-air density before the air enters the cylinders. The purpose is not simply to create more pressure; it is to supply the air volume required for efficient combustion, stable torque and controlled exhaust temperature under load. A correctly matched turbocharger therefore helps restore the engine's intended air-to-fuel relationship rather than masking an underlying fuel-system problem.

Primary engine fitment:

Caterpillar 3306 diesel engine

Selected Caterpillar 3306B configurations

Equipment associated with the 7N-7748 / 0R-5807 route includes D5B, D6D, D6E, D6F SR, D6G, D6H and D6G2 XL track-type tractors; 12G, 12H, 14G, 140G, 140H, 143H and 160H motor graders; and 966C or 966R wheel loaders. Actual compatibility still depends on the engine arrangement, serial-number range and original air-system configuration.

Configuration A

Turbo model: 3LM-373

Cat part number: 7N-7748

Cat Reman reference: 0R-5807

Common manufacturer references: 172495, 310135, 184119

Configuration B

Turbo model: 3LM-373

Cat part number: 8N-9247

Cat Reman reference: 0R-5811

Common manufacturer references: 172496, 313092, 185841

Published cross-reference information connects 7N-7748 with the 172495 version and 8N-9247 with the 172496 version, reinforcing the need to keep the two configurations separate during quotation and ordering.

Cat's matching Reman listings show a reference envelope of approximately 10.6 inches in length and 13.2 inches in height. These measurements are useful for comparison, but dimensions alone cannot determine fitment. The compressor outlet direction, turbine-housing orientation, mounting flange, oil-feed connection and oil-drain position must also match the removed unit.

The Caterpillar 3306 normally uses mechanically actuated individual injection pumps installed in a common pump housing rather than an electronically controlled high-pressure common-rail system. However, the diagnostic logic remains highly relevant to modern common-rail diesel service: injection quantity and available boost air must always be evaluated together.

Low boost, a restricted air filter, a leaking intake joint or an exhaust leak before the turbine may cause black smoke, poor load response and elevated exhaust temperature. Similar symptoms can also result from incorrect fuel delivery. Replacing injectors, an injection pump or a turbocharger without separating the air-side problem from the fuel-side problem often leads to repeat repairs.

On a modern diesel common-rail engine, technicians can compare commanded rail pressure, actual rail pressure, injection quantity and boost data. On a mechanical 3306, diagnosis relies more heavily on boost-pressure testing, smoke behavior, fuel-setting inspection and physical checks. The measurement methods differ, but the combustion principle remains the same: additional diesel fuel cannot burn efficiently without sufficient oxygen. BorgWarner's troubleshooting guidance likewise identifies air restrictions, intake leaks, exhaust restrictions and fuel-injection faults as possible causes of low boost and insufficient engine power.

Confirm every identification number visible on the original turbocharger.

Inspect the air cleaner, intake hose, exhaust manifold and charge-air path for debris, cracks or restrictions.

Clean or replace contaminated oil-feed components.

Verify that the oil-drain line runs freely downhill without kinks, sharp bends or undersized passages.

Pre-lubricate the bearing housing with clean engine oil and establish oil circulation before normal start-up.

Install new sealing gaskets and keep liquid sealant away from lubrication passages.

After starting, inspect all oil, intake and exhaust connections before applying full engine load.

A new turbo cannot compensate for a contaminated lubrication circuit, restricted drain, excessive crankcase pressure or foreign-object damage. BorgWarner notes that restricted oil return and excessive blow-by frequently cause oil leakage that may be incorrectly blamed on the turbo itself. Pre-lubrication is also recommended before placing a fresh turbo installation into service.

1. Are 7N-7748 and 8N-9247 the same turbocharger?

They are associated with the 3LM-373 family, but they use different Cat, Reman and manufacturer reference routes. Check the old unit, engine arrangement and housing orientation before ordering.

2. Will this turbo fit every Caterpillar 3306 engine?

No. The 3306 was produced for numerous machines, ratings and engine arrangements. The engine serial number, arrangement number, equipment model and original turbo identification should all be verified.

3. Is the Caterpillar 3306 a common-rail engine?

Typical 3306 fuel systems are mechanical rather than electronic high-pressure common rail. Nevertheless, turbocharger airflow remains closely connected to fuel-system performance because insufficient air affects smoke, combustion temperature and the amount of fuel that can be burned efficiently.

4. Does black smoke prove that the turbocharger has failed?

No. Black smoke may be caused by low boost, an intake restriction, an exhaust leak, incorrect fuel settings, injector problems or excessive engine loading. The complete intake, exhaust and injection systems should be tested first.

5. Can the original turbo oil lines be reused?

Only when they are clean, unrestricted and undamaged. A blocked feed or restricted drain can quickly damage a replacement turbo. Replacement is preferable when carbon deposits, contamination or deformation are found.

6. What information is required for an accurate quotation?

Provide the turbo nameplate, all visible part numbers, engine model and serial number, machine model, engine arrangement number, and clear photographs of the compressor outlet, turbine inlet and oil-port positions.

 

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