CUMMINS 4089977 GENUINE PISTON & RING KIT (.040 OVERSIZE) - OEM FOR 2003-2004 5.9L CUMMINS

The Cummins 4089977 Genuine Piston and Ring Kit (.040" Oversize) is the OEM solution for rebuilding high-mileage or damaged 5.9L Cummins common rail engines that require maximum cylinder reboring. This kit ensures proper compression, oil control, and long-term reliability.

Made from high-strength aluminum alloy and paired with precision-machined rings, this kit is ideal for stock replacements and towing builds.

Features & Benefits

• OEM Quality: Manufactured by Cummins for perfect fit and durability.
• Oversize Bore: Designed for cylinders bored .040" oversize.
• Complete Kit: Includes piston, wrist pin, circlips, and piston rings.

Cross Reference Part Numbers

• Cummins 4089977
• Replaces: 4089404, 4089975
• Interstate McBee M-4089977

Frequently Asked Questions

When should I use a .040 oversize piston?

Choose this size when your engine block requires the maximum allowable overbore (.040") to remove deep wear, scoring, or damage.

Can I use this kit for high-performance applications?

Yes, though forged aftermarket pistons may be a better choice for extreme boost or racing builds.

Do I still need to hone the cylinders?

Yes. Proper honing is essential for optimal ring seating and engine life.

Related Piston & Ring Kits for 2003-2004 5.9L Cummins

• Cummins 4089950 Genuine Piston & Ring Kit (STD) - OEM - Standard size for cylinders within factory spec.
• Cummins 4089976 Genuine Piston & Ring Kit (.020 Oversize) - OEM - For cylinders bored .020" oversize.
• Cummins 4089977 Genuine Piston & Ring Kit (.040 Oversize) - OEM - For cylinders bored .040" oversize.