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Toyota6.6L Duramax Flywheel Bolt Installation Guide (2001–2021) — FW100
This guide covers installation of the XOTIC PERFORMANCE™ FW100 flywheel bolt kit for the 6.6L Chevrolet / GMC Duramax. Prefer a printable copy? Download the PDF manual.
Threadlocker on the threads, lubricant under the head — two different products, two different places. The manual calls for Permatex Medium Strength Threadlocker BLUE on the bolt threads to resist vibration, and the supplied assembly lubricant under the bolt heads so the torque reading is accurate. Putting threadlocker under the head, or lubricant on the threads, gets you neither result.
Why flywheel bolts deserve attention
The flywheel bolts are the only thing holding a heavy spinning mass to the end of your crankshaft, and they see a load case most fasteners never do: constant torsional reversal. Every combustion event tries to accelerate the crank; the flywheel's inertia resists; the joint has to hold through both. On a diesel with a manual transmission, add clutch engagement shock on top of that.
When a flywheel bolt loosens, it does not fail quietly. The joint starts to fret, the bolt holes elongate, and the crank flange — a part you cannot replace without pulling the engine — gets damaged. This is a low-cost, high-consequence fastener, which is exactly the kind worth upgrading. XOTIC PERFORMANCE™ flywheel bolts are manufactured from our premium XOTIC 7200 steel alloy and backed by a lifetime warranty.
Before you start: verify first
Confirm that part number FW100 is compatible with your application before installing any components. Inspect all components for damage and report any issues to us before proceeding. Clean the crank flange and the flywheel's mating face — any oil film or debris between them changes how the joint clamps.
How to install flywheel bolts on a 6.6L Duramax
- Inspect first. Before installing any components, check for product damage and report anything you find.
- Apply threadlocker. Apply Permatex Medium Strength Threadlocker BLUE to the threads of each flywheel bolt to prevent them loosening due to vibration.
- Lubricate under the heads. Use the provided assembly lubricant under the head of each bolt. This reduces friction and allows for accurate torque readings.
- Fit the flywheel and hand-tighten. Place the flywheel onto the crankshaft and run all bolts in by hand before any torque goes on.
- Torque to 250 ft-lbs in a cross pattern. Work across the flywheel rather than around it, so pressure is distributed evenly as the joint pulls up.
Duramax flywheel bolt torque spec
| Fastener | Torque | Pattern |
|---|---|---|
| Flywheel bolts | 250 ft-lbs | Cross pattern |
A common mistake to avoid: torquing around the circle instead of across it. Going bolt-to-adjacent-bolt pulls one side of the flywheel down before the other and can leave the assembly sitting slightly cocked on the flange — which shows up later as runout and vibration. Always work in a cross pattern.
Frequently asked questions
What is the flywheel bolt torque spec for a 6.6L Duramax?
250 ft-lbs, applied in a cross pattern, with threadlocker on the threads and assembly lubricant under the bolt heads.
Why both threadlocker and lubricant?
They do different jobs in different places. Threadlocker on the threads stops the bolt backing out under vibration. Lubricant under the head controls the friction at the bearing face, which is where most of the torque you apply is actually consumed — without it, your wrench reads 250 ft-lbs long before the bolt has reached the intended clamp load.
Can I reuse the factory flywheel bolts?
We wouldn't. Flywheel bolts are cheap relative to the crank flange they protect, and the factory hardware has already been through its service life. If the flywheel is off, replace them.
Do I need to lock the crank while torquing?
Yes — 250 ft-lbs will turn the engine over otherwise. Use a proper flywheel holding tool rather than wedging something against the ring gear.
While the flywheel is off
See our 6.6L Duramax head stud guide (CP877) and the main stud guides for the LB7/LLY (MP877) and LBZ/LMM (MP881).
Need help?
For technical support, email support@xotic-performance.com. All XOTIC PERFORMANCE™ fasteners are covered by our limited lifetime warranty. Finished your install? Tag #XOTICPERFORMANCE on Instagram for a chance to be featured.
© 2026 XOTIC PERFORMANCE™. This installation guide is an original copyrighted work of XOTIC PERFORMANCE™. Reproduction, distribution, or use of this content in whole or in part without written permission is prohibited. Doc ref: 2025.10.21 (web edition 2026.08).
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