Product Description
Genuine Cummins
Cummins 3949688 — Rectangular Ring Seal (CP3 Injection Pump to Gear Housing)
MPN: 3949688 | Also Known As: CP3 gear access cover seal, rectangular O-ring
Why This Part
- ✓ OE sealing for the CP3-to-gear housing interface to prevent fuel/oil leaks.
- ✓ Direct-fit for 2003–2018 Ram ISB platforms (5.9L & 6.7L; see fitment).
- ✓ Rectangular-cross-section ring maintains seal under heat/cycle.
- ✓ Low-cost insurance any time the CP3 pump/cover is removed.
OE Fit Stock Replacement 1 Per Interface
Quick Specs
| Type | Rectangular ring seal (CP3 to gear housing) |
|---|---|
| OE Part # | 3949688 |
| Qty Required | 1 at CP3 gear access cover (sold individually) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 2003–2007 | Ram 5.9L ISB (24V Common-Rail) | Ram 2500/3500 |
| 2007.5–2018 | Ram 6.7L ISB (24V Common-Rail) | Ram 2500/3500 |
Industrial/Off-Highway: Also used on ISB/QSB applications—confirm by ESN.
Often Paired With
- CP3 gear access cover seal (round): Cummins 3946689
- Oil cooler gaskets: 3864458/4895742 (5.9L) · 3974127/2830559 (6.7L)
- Fresh oil/filter after major fuel/oil system service
What’s In The Box
- (1) Genuine Cummins Rectangular Ring Seal (3949688)
Install Tips
- Clean the groove; lightly lube the seal with clean oil before install.
- Seat evenly; avoid twisting the ring. Inspect mating surfaces for nicks.
- Replace any time the CP3/cover is removed to prevent seepage.
FAQ
WILL THIS FIT 2003–2018 RAM 5.9L/6.7L?Yes—it’s commonly used on ’03–’18 Ram ISB platforms at the CP3 gear access cover (verify by VIN/ESN).
IS THIS THE “RECTANGULAR” SEAL? WHAT’S DIFFERENT?Correct—3949688 uses a rectangular cross-section to maintain clamp load. It’s distinct from the round CP3 cover O-ring (3946689).
HOW MANY DO I NEED?One per CP3 gear access cover interface. Replace whenever the cover/pump is removed.
IS THIS A GENUINE CUMMINS PART?Yes—OE Cummins 3949688 for proper fit and long service life.
DOES THIS ALSO APPLY TO INDUSTRIAL ISB/QSB?Yes—this ring is also used on many ISB/QSB engines outside of automotive; confirm by ESN.
Product Videos
Custom Field
Vehicle Year 2003,2004,2005,2006,2007,2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018
Vehicle Make DODGE
ENGINE 5.9L,6.7L
