Product Description
CUMMINS 4089976 OEM PISTON & RING KIT (.020 OVER) – ISB 5.9L 305HP (2003–2004)
Upgrade your 2003–2004 Ram 2500/3500 5.9L ISB with the genuine CUMMINS 4089976 OEM piston & ring kit (.020 over) engineered specifically for the 305 HP common-rail calibration. This single-cylinder service kit includes the piston, matched ring pack, wrist pin, and retainers so you can restore compression, sealing, and durability after a proper overbore.
Why Choose Genuine Cummins 4089976?
- Direct-fit .020" over (+0.50 mm) piston & ring kit for 2003–2004 ISB 5.9L 305 HP Ram trucks.
- Correct bowl shape and compression ratio for OEM 305 HP common-rail tuning.
- Matched ring pack for strong sealing, low oil consumption, and long service life.
- Includes hardened wrist pin and retainers for a complete cylinder solution.
- Genuine Cummins metallurgy, heat-treat, and QC—no guessing, no shortcuts.
Fitment Details
Primary Automotive Fitment:
- Engine: Cummins ISB 5.9L, 24-valve common-rail, 305 HP rating
- Years: 2003–2004 (primarily 2003–early 2004 305 HP calibrations)
- Chassis: Dodge Ram 2500 & Ram 3500 pickup
Industrial / Off-Highway Fitment:
- Used on various Tier 2 ISB/QSB 5.9L applications and select 4B/6B/ISB families (verify by ESN/CPL).
- Common CPL/E-code associations: 2998, 8213 (always confirm using engine serial number).
Important: This is a .020" overbore (+0.50 mm) piston kit. Block machining (bore/hone) is required. Always verify piston spec, bore size, and CPL/ESN before ordering.
Cross-Reference Cummins Genuine Parts (On CPP Diesel)
- Standard-bore OEM piston kit for 03–04 305 HP: CUMMINS 4089950 OEM PISTON KIT (STANDARD) – ISB 5.9L 305HP (2003–2004)
- .040" over OEM piston kit for 03–early 04 305 HP: CUMMINS 4089977 OEM PISTON KIT (.040 OVER) – ISB 5.9L 305 HP (2003–EARLY 2004)
- Recommended Cummins ring set for .020" over ISB 5.9L: CUMMINS 4089181 OEM PISTON RING SET (.020 OVER) – RAM 5.9L ISB (2003–2007)
- Related OEM sensor used on 03–04 ISB 5.9L: CUMMINS 4897224 OEM COOLANT TEMPERATURE SENSOR – ISB 5.9L (2003–2004)
- Later-design .020" over piston kit for 04.5–07 ISB 5.9L: CUMMINS 4089670 OEM ENGINE PISTON KIT (.020 OVER) – 5.9L CUMMINS (2004.5–2007)
What's Included
- (1) Cummins OEM piston – .020" over (+0.50 mm)
- (1) Matched piston ring set
- (1) Hardened wrist pin
- (2) Pin retainers / locks
Installation Notes
- Have the block professionally bored and honed to Cummins spec for .020" over pistons.
- Measure and set piston-to-wall clearance per Cummins service manual.
- Check ring end gaps and file-fit as needed for your target application.
- Confirm piston orientation (bowl/relief and directional arrows) before final assembly.
- Verify CPL/ESN and piston spec before ordering a full set of six kits.
Specifications for cummins 4089976
| Attribute | Value |
|---|---|
| Brand | Cummins Genuine Parts |
| Part Number (MPN) | 4089976 |
| Product Type | Piston & Ring Kit – Single Cylinder |
| Bore Size | .020" over / +0.50 mm (overbore) |
| Engine Platform | Cummins ISB 5.9L (305 HP common-rail), Tier 2 ISB/QSB 5.9 (select applications) |
| Automotive Fitment | 2003–2004 Dodge Ram 2500/3500 with 5.9L ISB 24V common-rail, 305 HP |
| CPL / E-Codes | Common CPLs: 2998, 8213 (verify for your ESN) |
| Cross Reference (OE / Aftermarket) | Cummins 4089183 (superseded), PAI 111545-100, related Cummins kits 4089950 (standard bore), 4089977 (.040" over) |
| Quantity Required Per Engine | 6 kits (sold individually) |
| Package Weight (Approx.) | ~3.1 lb (single-cylinder kit) |
| Package Dimensions (Approx.) | 5.75 in x 5.75 in x 8.0 in |
| Shipping Info | Ships from CPP Diesel; typically leaves warehouse in 1–2 business days. Free shipping in the lower 48 states. |
| UPC | Not specified by Cummins (contact us if you require the carton UPC) |
| GTIN / EAN | Not published (GTIN not provided in available manufacturer data) |
| Prop 65 | WARNING: This product can expose you to chemicals including engine exhaust and byproducts which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov. |
FAQ
WILL THIS FIT MY 2003–2004 5.9L CUMMINS RAM?
Yes, this kit is designed for 2003–2004 Ram 2500/3500 trucks with the 5.9L ISB 24V common-rail rated at 305 HP. Some 2004 California-emissions trucks use different pistons, so always verify by VIN/ESN and CPL.
HOW MANY CUMMINS 4089976 KITS DO I NEED FOR A FULL REBUILD?
Each CUMMINS 4089976 kit services one cylinder. You will need six (6) kits for a complete 6-cylinder 5.9L engine rebuild.
DO I HAVE TO BORE AND HONE THE BLOCK FOR .020" OVER?
Yes. This is a .020" over (+0.50 mm) piston. The block must be bored and honed to the correct oversize, and piston-to-wall clearance must be set per the Cummins service specification.
WHAT IF MY ENGINE IS STILL STANDARD BORE?
If your cylinders measure within standard spec and you are not overboring, use the standard-bore OEM kit CUMMINS 4089950 instead of 4089976.
CAN I MIX STANDARD AND OVERBORE PISTONS?
No. Cylinder bores and pistons must match size. You cannot mix standard and .020" over pistons in the same hole. Each cylinder that is bored .020" over must use a 4089976 kit and the corresponding overbore ring set.
IS THIS A GENUINE CUMMINS PISTON & RING KIT?
Yes. This is a genuine Cummins OEM kit with Cummins-boxed piston, rings, wrist pin, and retainers. CPP Diesel sources directly from trusted Cummins distribution channels so you get authentic parts, not knockoffs.
