Product Description
Cummins 4932378 — Connecting Rod Bearing (.040 Undersize / 1.00 mm)
MPN: 4932378 | Type: Connecting rod bearing shell (upper) | Also Listed As: BEARING, CON ROD (040) | Common Cross-Refs: 3901174, 3901234
Why This Part
- ✓ OE material & geometry for proper oil clearance and film strength.
- ✓ .040" undersize / 1.00 mm for ground crank journals (repair size).
- ✓ Direct-fit for 1989–2002 Ram 5.9L ISB (machined rods).
- ✓ Restores bearing support & durability under towing and heavy load.
Quick Specs
| Application | Cummins B-Series 5.9L (automotive focus below) |
|---|---|
| OE Part # | 4932378 (upper shell) |
| Size | .040" undersize (1.00 mm) |
| Qty Needed | 6 uppers + 6 lowers per engine (sold individually) |
| Notes | Match with the correct lower shell P/N; verify by ESN and rod style (machined vs. fractured). |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 1989–2002 | 5.9L Cummins ISB (12V & 24V, machined rods) | Ram 2500/3500 |
Compatibility Notes: Designed for engines using machined connecting rods (common to ’89–’02). 2003+ engines often use fractured rods and different bearing shells—verify by VIN/ESN.
Often Paired With
- Matching lower rod bearing (.040): verify ESN/rod style to select the correct lower shell P/N.
- Main bearings & thrust set: replace during overhaul for balanced clearances.
- ARP or OE rod bolts: replace torque-to-yield hardware during reassembly.
- Oil & filter: change after initial run-in.
What’s In The Box
- (1) Genuine Cummins Connecting Rod Bearing Shell (Upper) – 4932378 (.040"/1.00 mm)
- Lowers, mains, and hardware sold separately.
Install Tips
- Confirm crank journal size and .040"/1.00 mm undersize before ordering.
- Cleanliness is critical; use plastigage or mic tools to verify clearance.
- Lubricate bearing surfaces; torque fasteners to factory spec.
- Prime oil system; monitor pressure on first start.
FAQ
WILL THIS FIT MY 1989–2002 5.9L CUMMINS RAM?Yes—4932378 is an OE rod bearing shell commonly used on 5.9L B-Series with machined rods. Always verify by VIN/ESN and journal size.
IS 4932378 AN UPPER OR LOWER BEARING?It’s typically the upper shell in a .040"/1.00 mm undersize. Pair with the correct lower shell for a complete rod bearing set.
WHAT DOES “.040 UNDERSIZE / 1.00 MM” MEAN?It matches a crankshaft that has been ground 0.040" (1.00 mm). Use only after confirming journal size.
DO I NEED BOTH UPPER & LOWER BEARINGS?Yes—engines require 6 uppers + 6 lowers. This listing is for a single shell; order the matching lowers separately.
WILL THIS WORK ON 2003+ 5.9L/6.7L?Some later ISB/QSB applications use different bearings due to fractured rod design. Verify by VIN/ESN before ordering.
IS THIS A GENUINE CUMMINS PART?Yes—OE Cummins 4932378 bearing shell.
