Product Description
Cummins 4955856 — Main Bearing Set (.010" / 0.25 mm Undersize)
MPN: 4955856 | Also Known As: main bearings set, crankshaft main bearing kit | Size: .010" under (0.25 mm)
Why This Part
- ✓ OE main bearing set for B-Series/ISB bottom-end rebuilds.
- ✓ .010" / 0.25 mm undersize for reground crank journals.
- ✓ Full set coverage for consistent oil clearances across all mains.
- ✓ Designed to restore oil pressure and film strength after machining.
Quick Specs
| Type | Main bearing set (crankshaft) |
|---|---|
| OE Part # | 4955856 |
| Size | .010" under / 0.25 mm undersize (for reground crank) |
| Includes | Upper & lower main shells; set is typically supplied with matching thrust (verify contents by ESN) |
| Qty Required | 1 set per engine |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 1989–1993 | 5.9L 12-Valve (VE pump) | Ram 2500/3500 |
| 1994–1998 | 5.9L 12-Valve (P7100) | Ram 2500/3500 |
| 1998.5–2002 | 5.9L 24-Valve (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 |
Industrial/Off-Highway: B/ISB family (4B/6B/ISB6.7) also use this size set in many applications—verify by ESN and crank grind size (.25 mm under) before ordering.
Often Paired With
- Thrust (std) if mixing sizes: 4938948 (confirm size needed)
- Rod Bearings (match size): common .010"/.25 mm sets available
- Lower Engine Gasket Sets: 3802376 (’94–’98), 4089173 (’03–’07), 4955355 (’07.5–’10), 4955522 (’11–’12), 4376091 (’13–’18)
- Assembly Lube & Plastigage to verify clearances
What’s In The Box
- (1) Cummins Main Bearing Set 0.25 mm undersize (.010") for B/ISB
- Typical kit includes main shells and thrust components; verify by ESN.
Install Tips
- Confirm crank is ground to .010" under; measure journals and saddles.
- Trial-fit and Plastigage every journal; target OE clearances.
- Clean oil passages; use assembly lube; torque caps in sequence to spec.
- After first heat cycle, recheck oil pressure and leaks.
FAQ
WILL THIS FIT MY CUMMINS 5.9L OR 6.7L RAM?Yes—this set is for the B-Series/ISB platform used in 1989–2018 Ram 2500/3500 models. Always verify by VIN/ESN and crankshaft grind size (.010" under).
IS 4955856 THE .010" (0.25 MM) UNDERSIZE?Correct—4955856 is the .010" / 0.25 mm undersize main bearing set intended for reground crankshafts.
DOES THIS SET INCLUDE THE THRUST BEARINGS?Most Cummins .25 mm kits include matched thrust components. Always verify kit contents by ESN and parts breakdown for your engine.
NEED STANDARD OR .020" INSTEAD?Standard is commonly 4955855; .020" under is commonly 4955857. Match size to your crank machining.
CAN I MIX SIZES BETWEEN MAINS AND THRUST?Yes, but you must order the correct individual thrust size if it’s different. Keep each journal’s pair matched, and verify clearances.
