Product Description
Cummins 3963379 — Rocker Lever Cover Gasket (Rocker Box to Cylinder Head)
MPN: 3963379 | Also Known As: rocker box gasket, valve/rocker cover lower gasket | Related/Cross-Refs (ID only): 3955109, 131692
Why This Part
- ✓ OE sealing between the rocker lever housing (“rocker box”) and the cylinder head.
- ✓ Direct-fit for Ram 5.9L/6.7L ISB—stops seepage and keeps the valve train clean.
- ✓ Durable OEM material designed for heat and oil resistance.
- ✓ Prevents leaks that can coat the engine and degrade hoses/belts.
Quick Specs
| Type | Rocker lever housing gasket (rocker box to head) |
|---|---|
| OE Part # | 3963379 |
| Qty Required | 1 per engine (sold individually) |
| Material | OEM composite/elastomer (oil & heat resistant) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 2003–2024 | Ram 5.9L & 6.7L ISB (24V Common-Rail) | Ram 2500/3500 |
Notes: Cummins notes primary use on later EPA13+ ISB/QSB 6.7; many retailers show full 2003–2024 Ram coverage—verify by VIN/ESN if components have been changed.
Often Paired With
- Upper valve cover gasket: 3954324 (pairs with the lower rocker box gasket)
- PCV/CCV filter (6.7L service items)
- Brake-clean & lint-free wipes to prep sealing surfaces
What’s In The Box
- (1) Genuine Cummins Rocker Lever Cover Gasket (3963379)
- Other gaskets and hardware sold separately
Install Tips
- Clean mating surfaces thoroughly; remove old sealant/debris.
- Seat gasket evenly; torque rocker box fasteners to spec in sequence.
- Recheck for seepage after initial heat cycle.
FAQ
WILL THIS FIT MY 2003–2024 5.9L/6.7L RAM?Yes—retail fitment shows 2003–2024 Ram 2500/3500 with 5.9L/6.7L ISB. Cummins also notes primary usage on later EPA13+ ISB/QSB 6.7 variants—verify by VIN/ESN.
IS THIS THE LOWER GASKET UNDER THE ROCKER BOX?Correct—this seals the rocker lever housing (rocker box) to the cylinder head. The upper valve cover gasket (e.g., 3954324) is separate.
IS THIS A GENUINE CUMMINS PART?Yes—OE Cummins 3963379 for proper fit and long service life.
DO I NEED SEALANT?Follow Cummins service info. Most installs are dry on clean, flat surfaces; apply sealant only where OEM procedure specifies.
ANY SIGNS THE GASKET HAS FAILED?Oil seepage around the rocker box perimeter, burning oil smell, or residue on the block. Replace promptly to prevent mess and soft-part degradation.
