Product Description
Cummins 4955859 — Main Bearing Set (.040 Under Size / 1.00 mm)
MPN: 4955859 | Also Known As: crankshaft main bearing set, main bearings | Size: .040 U/S (≈1.00 mm)
Why This Part
- ✓ OE bearing geometry & overlay for quiet, durable operation.
- ✓ .040 under size set for cranks ground 1.00 mm undersize.
- ✓ ISB/QSB 5.9L & 6.7L coverage across 1989–2018 (verify by ESN).
- ✓ Includes thrust bearing to control endplay (see BOM below).
Quick Specs
| Type | Main bearing set (upper/lower shells + thrust) |
|---|---|
| OE Part # | 4955859 (.040 U/S / 1.00 mm) |
| Engine Families | Cummins B-Series: ISB/QSB 5.9L & 6.7L |
| Includes (typical BOM) | 4938936 ×4, 4938940 ×5, 4938952 ×1 (thrust) |
| Qty Required | 1 set per engine |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 1989–1993 | 5.9L 6BT 12V (VE-pump) | Dodge D/W 250/350 |
| 1994–1998 | 5.9L 6BT 12V (P7100) | Ram 2500/3500 |
| 1998.5–2002 | 5.9L ISB 24V (VP44) | Ram 2500/3500 |
| 2003–2007 | 5.9L ISB 24V (Common-Rail) | Ram 2500/3500 |
| 2007.5–2018 | 6.7L ISB 24V (Common-Rail) | Ram 2500/3500 |
Important: This is a .040 under size set for a crankshaft ground 1.00 mm undersize. Verify by ESN, crank grind size, and block line-bore/hone specs before ordering.
Often Paired With
- Standard size main set: Cummins 4955853 (if crank is STD)
- Rod bearings: 3969562 (ISB 5.9/6.7), 4893693 (6.7L)
- Oil pan gasket: 4934344 (B-Series)
- Fresh oil & filter; assembly lube; plastigage/micrometer for checks
What’s In The Box
- (1) Genuine Cummins Main Bearing Set 4955859 (.040 U/S / 1.00 mm)
- Includes upper/lower shells and thrust bearing (see BOM above)
Install Tips
- Confirm crank grind (.040" / 1.00 mm) and block line-bore/hone status.
- Cleanliness is critical—flush oil galleries, use assembly lube, and torque caps to spec.
- Measure oil clearance with mic/Plastigage; verify thrust endplay.
- Prime oil system and monitor oil pressure on first start.
FAQ
IS 4955859 THE RIGHT SIZE FOR MY BUILD?4955859 is the .040 under size (1.00 mm) main set. Use it only when the crank has been ground .040"/1.00 mm undersize. If your crank is standard, see 4955853 instead.
WILL THIS FIT BOTH 5.9L AND 6.7L ISB ENGINES?Yes—this set is cataloged for B-Series ISB/QSB 5.9L & 6.7L applications across 1989–2018, but always verify by ESN and bearing size before ordering.
DOES THE KIT INCLUDE THE THRUST BEARING?Yes—this kit includes the thrust bearing along with the main shells (see BOM).
WHAT IF I’M UNSURE OF MY SIZE?Measure the crank journals or consult your machine shop. Ordering the wrong size can cause oil pressure issues or failure.
IS THIS A GENUINE CUMMINS PART?Yes—OE Cummins 4955859 bearing set built to factory specs for fit and longevity.
