Product Description
Interstate-McBee M-3958645 Multi-Layer "Thick" Head Gasket – 2003–2007 5.9L Cummins ISB
Premium multi-layer steel (MLS) “thick” (Grade B) head gasket engineered to OEM form, fit, and function for 2003–2007 Dodge Ram 2500/3500 5.9L Cummins ISB (24-valve common-rail) engines. Ideal for rebuilds, resurfaced heads/blocks, or applications requiring the Grade-B thickness to maintain proper compression and piston-to-head clearance.
- OEM-style replacement: Interchanges with Cummins 3958645 (Grade B “thick”).
- MLS construction: Multi-layer stainless design with elastomer coating for durable sealing.
- Correct thickness grade: Grade-B (thick) selection for engines needing additional gasket height after machining.
- Fitment clarity: Built for 03–07 5.9L ISB common-rail; verify by engine serial number (ESN) for non-truck and QSB uses.
- Aftermarket value: Interstate-McBee quality at a lower cost than OEM boxed parts.
Specifications
| Manufacturer | Interstate-McBee |
|---|---|
| Part Number | M-3958645 |
| OEM Cross-Reference | Cummins 3958645 (Grade B / “Thick”) |
| Gasket Type | Multi-Layer Steel (MLS) |
| Thickness Grade | Grade B (“Thick”) |
| Identification | Two closely spaced hole marks (Grade-B identifier) |
| Also Referenced | 3954876 (alt. cross-ref.) |
| Position | Cylinder Head |
Vehicle Fitment
Always confirm by ESN, especially for industrial/ag applications.
- Dodge Ram 2500/3500 5.9L Cummins ISB (24-Valve Common-Rail):
- Model Years: 2003, 2004, 2005, 2006, 2007
- Industrial: Select QSB 5.9 applications may use 3958645 (verify by ESN).
Installation Notes
- Measure piston protrusion and surface finish; select Grade-B when required by spec.
- Follow Cummins service manual for head bolt torque sequence/angles and lubrication.
- Replace TTY head bolts or upgrade to studs; chase threads and check fastener stretch as applicable.
- Clean deck and head surfaces thoroughly; verify RA/Rz per OEM spec for MLS sealing.
What’s Included
- (1) Multi-Layer Steel head gasket, Grade B (thick)
Why Buy From CPP Diesel
- Diesel specialists with ESN-verified fitment support
- Fast shipping and easy returns
- Great bundle options with head bolts/studs, upper gasket sets, and coolant
FAQ
What does “thick” or Grade-B mean?Grade-B is the thicker OEM-specified head gasket grade for the 5.9L ISB. It’s commonly chosen after machining or when piston protrusion measurements require additional gasket height. Identify Grade-B by the two closely spaced hole marks on the gasket.
Will this fit all 2003–2007 5.9L Cummins trucks?
Yes—this gasket targets 2003–2007 Dodge Ram 2500/3500 with the 5.9L ISB common-rail. For industrial/ag (QSB) engines, confirm by ESN.
Do I need new head bolts or studs?
We strongly recommend new fasteners. Many builders upgrade to head studs on common-rail 5.9L engines for improved clamping and longevity.
Can I use this on an O-ringed or fire-ringed head?
Consult your machine shop and the Cummins manual. MLS gaskets can work with certain O-ringed setups, but fire-ring builds often require specific gaskets and procedures.
How do I choose the correct thickness grade?
Measure piston protrusion and follow the Cummins specification chart. If machining has reduced deck height or you need added clearance, Grade-B (thick) is typically specified.
Product Videos
Custom Field
YEAR 2003-2007
MAKE DODGE
ENGINE 5.9L
