Product Description
CUMMINS 3927948 OEM 12MM MAIN BEARING CAP BOLT – 5.9L/6.7L (1998.5–2018) is the factory main cap fastener your Ram bottom end was designed around. This genuine Cummins fracture-resistant screw clamps the main bearing caps with consistent torque and stretch so your 5.9L or 6.7L ISB can live at stock or tuned power levels without worrying about mystery hardware.
Featuring an M12 x 1.50 thread and 119 mm overall length, this bolt is the correct 12mm main cap hardware used on late 5.9L and all 6.7L Cummins blocks. It’s sold individually so you can replace a damaged fastener or order a full set of 14 for a complete rebuild. Pair it with genuine Cummins main bearings and thrust bearings to keep your crankshaft happy for another hundred thousand miles.
Key Features
- Genuine Cummins OEM fracture-resistant main bearing cap bolt (part number 3927948).
- Correct 12 mm main cap hardware for 5.9L/6.7L ISB bottom ends, not a generic “fits-all” bolt.
- M12 x 1.50 x 119 mm dimensions for proper thread engagement and clamping load.
- Sold individually – order 14 bolts per 6-cylinder engine (10 for most 4BT applications).
- Ideal for stock rebuilds, refreshes, and bottom-end reseals where OEM reliability matters.
Verified Fitment
Automotive – Dodge/Ram Trucks:
- 1998.5–2002 Ram 2500/3500 5.9L ISB (24-valve VP44) – 12mm main bearing cap bolt locations.
- 2003–2007 Ram 2500/3500 5.9L ISB (24-valve common-rail) – factory 12mm main cap hardware.
- 2007.5–2018 Ram 2500/3500 6.7L ISB (24-valve common-rail) – OEM main bearing cap bolts.
Industrial / Off-Highway:
- Used on many BS3 5.9L B-series and related ISB/QSB engines that call for a 12 mm main cap bolt – always confirm by engine serial number (ESN) and parts catalog before ordering.
Fitment Tip: If your block has 14 mm main cap hardware (early 12-valve 5.9L), use the dedicated 14 mm main cap bolt instead, such as the genuine CUMMINS 3904217 OEM MAIN BEARING CAP BOLT – 14MM – 5.9L 12V.
Cross-Reference & Recommended Cummins Bottom-End Parts
- Cross Reference: Often cross-referenced to Cummins OEM number 4891353 in aftermarket catalogs. Always match by ESN.
- For a full OE main bearing refresh, pair these bolts with:
Specifications for cummins 3927948
| Attribute | Value |
|---|---|
| Brand | Cummins ® Genuine OEM |
| Part Number | 3927948 |
| Alternate / Cross Reference | 4891353 (catalog cross reference – verify by ESN) |
| Type | Main bearing cap bolt (fracture-resistant screw) |
| Thread Size | M12 x 1.50 |
| Overall Length | 119 mm |
| Engine Families | 5.9L ISB, 6.7L ISB, select 4BT/6BT/ISB/QSB applications using 12 mm main bolts |
| Quantity Required | 14 per 6-cylinder engine (5.9L/6.7L), 10 per 4BT (sold individually) |
| GTIN / EAN | Not specified by Cummins for this service part |
| UPC | Not specified / not published in OEM or major distributor data |
| Package Dimensions (L x W x H) | Approx. 6.4 x 2.0 x 2.0 in |
| Package Weight | Approx. 0.26 lb (single bolt) |
| Shipping Method | Ships via standard ground parcel service; multiple bolts may ship in one carton |
| E-Codes / Emissions | Not emissions-critical; no specific E-code noted |
| Prop 65 | WARNING: Cancer and Reproductive Harm – www.P65Warnings.ca.gov |
Installation & Tech Notes
- Always clean the block threads and bolt threads before installation.
- Use appropriate engine oil or specified lubricant on threads and under the bolt head unless Cummins documentation states otherwise.
- Torque using the OEM procedure (torque + angle where specified) from the Cummins service manual for your ESN.
- Never mix 12 mm and 14 mm main cap hardware in the same block.
FAQ
How many Cummins 3927948 main cap bolts do I need for my engine?
A full 6-cylinder 5.9L or 6.7L ISB uses 14 of these 12 mm main bearing cap bolts. Most 4BT applications require 10. This listing is for a single bolt, so order the quantity you need for your build.
Will this bolt fit my 5.9L or 6.7L Ram Cummins?
If you have a 1998.5–2007 5.9L ISB or 2007.5–2018 6.7L ISB Ram 2500/3500, this is the correct 12 mm main bearing cap bolt for most engines. For absolute confirmation, match by engine serial number (ESN) or OEM parts lookup using Cummins 3927948.
Can I reuse my original main bearing cap bolts?
Many builders choose to replace main cap bolts any time the bottom end is apart. Even when not formally “torque-to-yield,” used bolts can be stretched, corroded, or damaged. For the cost of new OEM hardware, replacing with fresh 3927948 bolts is cheap insurance on a rebuild.
What torque specs should I use with these bolts?
Always follow the factory Cummins service manual for your specific ESN. Use the OE torque and angle sequence, including any lubrication requirements and multi-step tightening instructions. Do not rely on generic torque charts for critical bottom-end fasteners.
What other Cummins parts should I replace while I’m in the bottom end?
When the crank is out, it’s smart to install new main bearings, thrust bearings, and alignment dowels. Popular OEM pairings with these bolts include the CUMMINS 4955855 MAIN BEARING SET (STANDARD), CUMMINS 4938948 THRUST BEARING, and CUMMINS 3900068 RING DOWEL for precise main cap alignment.
