Product Description
Genuine CUMMINS 3903857 OEM VIBRATION DAMPER / FLYWHEEL MOUNTING BOLT – 5.9L 6BT/ISB (1989–2002) is the correct hex flange bolt for critical crankshaft interfaces on BS3 5.9L B-Series engines, including the harmonic balancer (vibration damper) and select flywheel/flexplate applications on 1989–2002 Dodge Ram 2500/3500 trucks. This is not generic hardware – it is the exact Cummins fastener engineered for proper clamp load, thread engagement, and long-term reliability under diesel torsional loads.
Features & Benefits
- Genuine Cummins hex flange head cap screw, engineered for BS3 5.9L B-Series engines.
- Correct M12 x 1.25 thread and under-head length for damper/flywheel service – no guessing on hardware.
- Heat-treated OE fastener designed to hold clamp load under diesel torsional vibration.
- Supports proper alignment of the vibration damper and flywheel/flexplate to help prevent fretting and loosening.
- Backed by Cummins quality control for consistent material and thread spec.
Verified Fitment
Automotive – Dodge Ram 5.9L Cummins
- 1989–1993 Dodge Ram 2500/3500 – 5.9L 12V Cummins (6BT)
- 1994–1998 Dodge Ram 2500/3500 – 5.9L 12V Cummins (6BT)
- 1998.5–2002 Dodge Ram 2500/3500 – 5.9L 24V Cummins ISB (VP44)
Industrial / Off-Highway
- BS3 5.9L B-Series engines, and select 4B/6B applications (verify by ESN before ordering).
Important Fitment Notes:
- This listing targets 1989–2002 5.9L trucks. Later 5.9L/6.7L engines can use different hardware – always confirm by VIN/ESN.
- Typical quantity: 4 bolts for the vibration damper. Flywheel/flexplate quantity may vary by transmission – confirm with the service manual.
- Replace removed bolts with new OE hardware whenever the damper or flywheel is serviced.
Cross-Reference & Related Cummins Components (CPP Diesel)
For a complete and reliable front-end and bottom-end service on your 5.9L Cummins, pair this bolt with other genuine Cummins components available at CPP Diesel:
- CUMMINS 3918999 OEM HARMONIC BALANCER (VIBRATION DAMPER) – 5.9L ISB (1998.5–2002)
- CUMMINS 3957544 OEM ENGINE OIL COOLER – 6BT/ISB 5.9L (1989–2002)
- CUMMINS 3938157 OEM OIL PICKUP TUBE FLANGE GASKET – 6BT/ISB 5.9L (1989–2002)
- CUMMINS 4939587 OEM ENGINE OIL PUMP – 5.9L 12V/24V (1989–2002) | 4BT/6BT
- CUMMINS 3904166 OEM CYLINDER REPAIR SLEEVE (SALVAGE SLEEVE) – 5.9L 4BT/6BT/ISB (1989–2007)
What’s Included
- (1) Genuine Cummins Hex Flange Head Cap Screw – Part Number 3903857
Installation Tips
- Clean threads in the crankshaft and on the new bolts; remove old thread locker and debris.
- Use thread locker only if specified by the Cummins or Dodge service manual for your ESN/VIN.
- Torque bolts in a star or crisscross pattern to the factory torque spec; follow any angle-torque instructions.
- When in doubt, always reference the latest Cummins service literature for your ESN.
Specifications for cummins 3903857
| Brand | Cummins Genuine Parts |
| Part Number | 3903857 |
| Product Type | Hex Flange Head Cap Screw (Vibration Damper / Flywheel Bolt) |
| Thread Size | M12 x 1.25 |
| Under-Head Length | Approx. 36 mm (1.425 in) |
| Engine Applications | 5.9L 6BT / ISB Cummins (BS3 B-Series), select 4B/6B – verify by ESN |
| Primary Vehicle Fitment | 1989–2002 Dodge Ram 2500/3500 with 5.9L Cummins |
| UPC | 725714358628 |
| GTIN | 725714358628 |
| Shipping Weight | Approx. 0.11 lb (0.05 kg) |
| Package Dimensions | Approx. 1.65 in x 0.90 in x 0.90 in |
| Shipping Info | Ships from CPP Diesel; shipping cost calculated at checkout; typically ships via standard ground service. |
| Cross Reference / Related Cummins Parts | Harmonic balancer: 3918999; Oil pump: 4939587; Cylinder repair sleeve: 3904166. |
| E-Codes | Not applicable (hardware fastener – no emissions or lighting E-mark). |
| Prop 65 | This product can expose you to chemicals including metal alloys and coatings which are known to the State of California to cause cancer and/or birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov. |
FAQ
WILL THIS BOLT FIT MY 1989–2002 5.9L CUMMINS RAM?
Yes. Cummins 3903857 is an OE hex flange bolt used on BS3 5.9L B-Series engines, including 1989–2002 12V and 24V ISB Ram 2500/3500 applications. Always confirm by VIN or engine serial number (ESN) if you are unsure or if your engine has been swapped.
HOW MANY BOLTS DO I NEED FOR THE HARMONIC BALANCER?
Most 5.9L B-Series crankshaft vibration dampers use four (4) of these bolts. Always count the bolts on your engine and follow the torque sequence from the factory service manual.
CAN THIS BOLT ALSO BE USED ON THE FLYWHEEL OR FLEXPLATE?
Cummins 3903857 is referenced for both damper and certain flywheel/flexplate interfaces on B-Series engines. Transmission type and model year can change the hardware used, so verify with your VIN/ESN or Cummins documentation before using it as a flywheel/flexplate bolt.
WHAT IS THE THREAD SIZE AND LENGTH OF THIS BOLT?
The bolt is M12 x 1.25 with an approximate under-head length of 36 mm (about 1.425 inches). This matches the OE specification for BS3 5.9L damper hardware.
IS THIS A GENUINE CUMMINS PART OR AFTERMARKET?
CPP Diesel supplies genuine Cummins 3903857 hardware for this listing – not a universal or off-brand bolt. You get OE material, heat treatment, and dimensions designed for your 5.9L Cummins.
