Product Description
CUMMINS 4089671 OEM ENGINE PISTON KIT (.040 OVER) – RAM 5.9L (2004.5–2007)
The genuine CUMMINS 4089671 OEM .040 over piston kit is the factory-engineered oversize piston assembly used when rebuilding worn or damaged 2004.5–2007 5.9L Cummins ISB engines. Oversize pistons restore proper cylinder sealing, compression, and durability when cylinders have been bored to .040" over during machining. When it comes to engine internals, only true OEM Cummins pistons deliver the metallurgy, skirt coating, weight matching, and ring compatibility required for long-term reliability.
This complete piston kit includes the correct .040" oversize piston, rings, and pin components engineered specifically for the 2004.5–2007 common-rail 5.9L. Whether you’re doing a full overhaul, repairing scuffed cylinders, or rebuilding a high-mileage 24-valve, this OE piston kit ensures factory performance and service life.
Key Features
- .040" oversize piston kit for machining and cylinder overhaul.
- Genuine Cummins OEM piston with correct alloy, skirt coating, and weight spec.
- Direct replacement for 2004.5–2007 ISB 5.9L common rail engines.
- Includes rings and wrist pin components for a complete piston assembly.
- Restores compression, sealing, and engine efficiency.
Fitment Details
- Engine: Cummins 5.9L ISB Common Rail (24-Valve)
- Years: 2004.5–2007
- Vehicle Applications: Dodge/Ram 2500 & 3500
- Notes: Used ONLY in engines bored .040" over. Always confirm with your machine shop and VIN/ESN.
Cross-Reference & Companion Cummins Parts
CPP Diesel provides all major Cummins components needed for a complete 5.9L rebuild. Pair CUMMINS 4089671 with these verified working Cummins OEM parts:
- CUMMINS 4089153 ENGINE MAIN BEARING SET
- CUMMINS 4955859 CONNECTING ROD BEARING SET
- CUMMINS 4089649 PISTON RING SET (STANDARD) – shows ring format consistency
- CUMMINS 3929011 WRIST PIN BUSHING
- VIEW ALL GENUINE CUMMINS OEM PARTS
Common Cummins supersessions: 4089671, 4089671NX (reman). Always confirm piston size and compatibility via VIN/ESN.
Installation Notes
- Requires machine shop confirmation of .040" cylinder overbore.
- Check piston-to-wall clearance per Cummins service specifications.
- Always measure ring end gap before installation.
- Replace wrist pin bushings and connecting rod bearings during rebuild.
- Professional machining strongly recommended for best results.
Specifications for cummins 4089671
| Attribute | Value |
|---|---|
| Brand | Cummins (Genuine OEM) |
| Cummins Part Number | 4089671 |
| Oversize | .040" Over (1.00 mm over standard) |
| Function | Complete piston, ring, and wrist pin kit for 5.9L ISB |
| Engine Compatibility | 5.9L Cummins ISB (2004.5–2007) |
| Vehicle Fitment | Dodge/Ram 2500 & 3500 |
| UPC | 190910289353 |
| GTIN | 190910289353 |
| Shipping Weight | Approx. 1.9 lbs per piston |
| Shipping Method | Standard ground; heavy-duty items ship insured |
| E-Codes / Emissions | Non-emissions component |
| Prop 65 Warning | WARNING: This product may expose you to chemicals known to the State of California to cause cancer and reproductive harm. Visit www.P65Warnings.ca.gov. |
| Country of Origin | As labeled by Cummins (varies by production batch) |
Frequently Asked Questions
WILL THIS PISTON KIT FIT MY 2004.5–2007 5.9L CUMMINS?
Yes — as long as your engine has been machined to .040" over. Always verify piston size using your VIN/ESN and machine shop measurements.
WHAT DOES .040 OVER MEAN?
It indicates the cylinder has been bored .040" (1.00 mm) larger than stock to clean up wear, scoring, or distortion.
SHOULD I REPLACE ALL PISTONS AT ONCE?
Yes — Cummins recommends replacing pistons as a set to maintain balance, weight matching, and combustion uniformity.
WHAT OTHER PARTS SHOULD I REPLACE DURING A REBUILD?
We recommend main bearings, rod bearings, wrist pin bushings, and inspecting the crankshaft, rods, and cylinder head components.
IS THIS A GENUINE CUMMINS PART?
Yes — CPP Diesel sells only authentic Cummins OEM piston kits for maximum durability and accuracy.
