Product Description
The Cummins 4955858 OEM Main Bearing Set (.030 undersize) is a genuine crankshaft main-bearing kit engineered for 5.9L and 6.7L Cummins engines requiring a .030" undersize bearing during a crankshaft grind or full engine rebuild. These bearings are manufactured to Cummins’ strict metallurgy and lubrication-channel specifications, ensuring long-term durability, correct oil clearances, and optimal crankshaft support under towing, work, or performance loads. When restoring an engine with worn journals, only a genuine Cummins bearing set guarantees OE fitment, reliability, and consistent oil film control.
Fitment
- 1989–1998 5.9L 12-Valve Cummins (6BT)
- 1998.5–2002 5.9L 24-Valve Cummins (ISB)
- 2003–2007 5.9L ISB Common Rail Cummins
- 2007.5–2018 6.7L ISB Cummins (RAM 2500/3500/4500/5500)
- Industrial and off-highway B-Series engines (ESN verification recommended)
Note: This is a .030" undersize bearing set. Verify crankshaft machining measurements before ordering.
Cross-Reference (Cummins-Only)
Other Cummins internal engine components commonly replaced together:
• Cummins 3900267 OEM Tappet Cover Grommet Seal
• Cummins 3903924 OEM Timing Pin – 12V
• Cummins 3904408 OEM Valve Stem Guide – Long
• Cummins 3904409 OEM Valve Stem Guide – Short
FAQ
What does “.030 undersize” mean for main bearings?
This means the crankshaft has been ground .030” undersize on the main journals and requires a bearing set sized accordingly for proper oil clearance.
Can I use .030 bearings on a standard crankshaft?
No. Undersize bearings are only for cranks that have been machined. Installing them on a standard crank will cause binding and catastrophic engine failure.
Is this bearing set compatible with both 5.9L and 6.7L Cummins engines?
Yes. Cummins 4955858 fits 5.9L (1989–2007) and 6.7L (2007.5–2018) engines requiring .030" undersize bearings.
Should rod bearings be replaced at the same time?
Yes. During any rebuild, Cummins recommends replacing rod bearings and inspecting thrust bearings to ensure full lubrication-system restoration.
Are these genuine Cummins bearings?
Yes. These are OEM Cummins bearings, not aftermarket replacements, ensuring proper oil groove placement, tolerances, and load capacity.
Specifications for cummins 4955858
| Specification | Value |
|---|---|
| Brand | Cummins Genuine Parts |
| Part Number | 4955858 |
| Bearing Size | .030 Undersize |
| UPC | Not Published |
| GTIN | Not Published |
| Cross Reference | Used across 5.9L/6.7L Cummins B-Series requiring .030 bearings |
| E-Codes | N/A |
| Shipping Weight | 1.5 lbs |
| Package Dimensions | 5 x 4 x 3 in |
| Prop 65 Warning | Not Applicable |
