Cummins Isx Flywheel Housing Torque Specs [2024]

Before commencing any work, ensure the following safety protocols are observed:

Use a star pattern similar to a wheel lug pattern. Tighten bolt #1, then the bolt opposite it, crisscrossing the flywheel face to ensure the flywheel seats flat against the crank flange.

The flywheel housing (also called the rear gear housing or clutch housing) is the structural bridge between the engine block and the transmission. On an ISX, which produces up to 2,050 lb-ft of torque, this housing must withstand extreme torsional vibration.

Incorrect torque causes:

The flywheel housing on a Cummins ISX must be torqued using the torque-plus-angle method: 55 N·m then 90° for M12 bolts. Direct torque values alone are insufficient due to friction variations. Following the specified sequence, dowel alignment, and flange sealant application ensures leak-free operation and proper drivetrain alignment for the engine’s service life.

Disclaimer: This paper is a technical summary. Always consult the latest Cummins service manual (e.g., Bulletin 4021931, 4021932) for your specific engine serial number, as ISX generations (CM570, CM870, CM871, CM2250, CM2350) have minor variations.

References

End of paper.

These bolts attach the aluminum or cast iron housing to the rear of the engine block.

| Component | Bolt Size / Type | Torque (Nm) | Torque (lb-ft) | Notes | | :--- | :--- | :--- | :--- | :--- | | Housing to Block (M10) | M10 x 1.5 (8.8 or 10.9 grade) | 54 Nm | 40 lb-ft | Standard spec | | Housing to Block (M12) | M12 x 1.75 | 95 Nm | 70 lb-ft | Used on larger housings | | Revised spec (many ISX) | M10 (with thread locker) | 75 Nm | 55 lb-ft | Common in later service bulletins | Cummins Isx Flywheel Housing Torque Specs

Critical: Always clean blind holes in the block (oil/debris causes hydraulic lock and cracks the housing). Apply Loctite 242 (blue) or equivalent to bolt threads unless specified otherwise.

| Component | Torque (Nm) | Torque (lb-ft) | | :--- | :--- | :--- | | Starter through-bolts (M12) | 54 Nm | 40 lb-ft | | Starter to housing (M10) | 46 Nm | 34 lb-ft |

Some ISX use M16 starter bolts → torque 180 Nm (133 lb-ft). Check your starter flange. Before commencing any work, ensure the following safety

Disclaimer: This content is for informational purposes only. Always consult the official Cummins ISX/Signature/QSX Service Manual (Bulletin 3666113 or equivalent) for your specific engine serial number, as specifications can change by model year.