Duramax LMM Knocking: Injector or Cracked Flex-plate? Pt.1 Diagnosis - Chevy and GMC Duramax Diesel Forum
07.5-10 LMM Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

View Poll Results: What is the problem Knock?
Flex-plate cracked or bolts loose 1 33.33%
Injector Knock 1 33.33%
CP3 Pump issue or sensor 0 0%
Engine bottom end 2 66.67%
Something else 0 0%
No clue and good luck! 0 0%
Multiple Choice Poll. Voters: 3. You may not vote on this poll

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post #1 of 12 (permalink) Old 12-09-2019, 09:05 PM Thread Starter
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Duramax LMM Knocking: Injector or Cracked Flex-plate? Pt.1 Diagnosis

Hello DuramaxForum community. This is my first post, and for good reason.. I've been on this forum as a spectator looking for information to help diagnose my Duramax knock. After much research and visiting shops, I have made my own conclusion and will be dropping the Allison Transmission tomorrow. Please check out my Diagnosis video linked next.

Duramax LMM Knocking: Injector or Cracked Flex-plate? Pt.1 Diagnosis
See VIDEO: https://www.patreon.com/posts/duramax-lmm-or-1-32224165 /

Injector Knock or Cracked Flex-Plate diagnosis w/ 2009 Chevrolet Duramax LMM Dually. Give a guess in the comments section and stay tuned for Pt.2 where we drop the Allison Transmission to inspect and install new parts.

Removing the Allison transmission in a Duramax is a lot of work, so I better install some performance parts while i'm at it for preventative maintenance and improved driveability.

This episode we inspect the new Torque Converter and Flex-plate I ordered from #suncoastdiesel out of Florida to my location in Kelowna BC Canada. Featuring the GM-107X-3D billet triple-disc low stall 1800 RPM tight stator designed for towing applications., To be paired with the Suncoast Performance Diesel LBZ/LMM billet counter-balanced flex-plate. #injectorknock #crackedflexplate #duramaxknock

With changing to a 1800 RPM Low Stall performance stator from the OEM's 2200 RPM stator I hope to see a fuel mileage improvement.
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post #2 of 12 (permalink) Old 12-29-2019, 08:20 PM Thread Starter
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Duramax LMM Knocking Pt.2: Allison Transmission Removal Ep.1
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post #3 of 12 (permalink) Old 12-29-2019, 08:22 PM Thread Starter
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Duramax LMM Knocking Pt.3: Allison Transmission Removal Ep.2
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post #4 of 12 (permalink) Old 12-29-2019, 09:35 PM
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Sounds like injectors knock to me or even worse, rod knock!!!! Good luck with the fix.
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Justin 2001 LB7 Silverado 2500HD LT CCSB 4x4.
EFI Live by Idaho Rob, 536K+ and rolling, Undercover Bed Cover, Vortex spray in bed liner, Odyssey Extreme Batteries, Westin steps, Bilstein Shocks, Road Master Active Suspension, M/A Pump Rub Kit, PPE Trans Cooler, MBRP 5" Exhaust, Edge Insight CTS, K&N drop in filter, AirDog II 100 w/ CAT 751, LLY FF Housing w/ Racor, Running on LMM Blacked out Wheels & Michelin LTX M/S2 tires.
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post #5 of 12 (permalink) Old 12-29-2019, 10:43 PM Thread Starter
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Duramax LMM Knocking Pt.4: Suncoast Diesel 1800-Low-Stall Converter & Billet Flex-plate Installation

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post #6 of 12 (permalink) Old 01-04-2020, 06:56 PM
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So, $4,000 in parts and labor and is it still knocking? Not saying the Suncoast converter is a waste of money, but this seems like just a ploy for youtube views and patreon $$$$.
Who diagnosed the "cracked" flex plate?
Have the injectors even been checked?
You can turn them off one at a time with a scan tool to see which one could potentially be knocking.
Just my $0.02 (USD).

Justin 2001 LB7 Silverado 2500HD LT CCSB 4x4.
EFI Live by Idaho Rob, 536K+ and rolling, Undercover Bed Cover, Vortex spray in bed liner, Odyssey Extreme Batteries, Westin steps, Bilstein Shocks, Road Master Active Suspension, M/A Pump Rub Kit, PPE Trans Cooler, MBRP 5" Exhaust, Edge Insight CTS, K&N drop in filter, AirDog II 100 w/ CAT 751, LLY FF Housing w/ Racor, Running on LMM Blacked out Wheels & Michelin LTX M/S2 tires.
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post #7 of 12 (permalink) Old 01-11-2020, 06:08 PM
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Watched part 5 or 6 and saw cylinder #5 (passenger side, 3 back) had a balance rate of 16! That's a bad stick and that would cause the knock. If you don't replace it you can melt a piston.....

Justin 2001 LB7 Silverado 2500HD LT CCSB 4x4.
EFI Live by Idaho Rob, 536K+ and rolling, Undercover Bed Cover, Vortex spray in bed liner, Odyssey Extreme Batteries, Westin steps, Bilstein Shocks, Road Master Active Suspension, M/A Pump Rub Kit, PPE Trans Cooler, MBRP 5" Exhaust, Edge Insight CTS, K&N drop in filter, AirDog II 100 w/ CAT 751, LLY FF Housing w/ Racor, Running on LMM Blacked out Wheels & Michelin LTX M/S2 tires.
ADRENALINE TRUCK PERFORMANCE
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post #8 of 12 (permalink) Old 01-12-2020, 11:47 AM Thread Starter
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Quote:
Originally Posted by Earnhardtfan View Post
Watched part 5 or 6 and saw cylinder #5 (passenger side, 3 back) had a balance rate of 16! That's a bad stick and that would cause the knock. If you don't replace it you can melt a piston.....

ahh you missed the whole story of that segment (Disabling each injector at a time with the Tech2) which puts all the other injectors balance rates into a haze.
To clarify my words, it showed balance rate of 16 when another injector was disabled.


Thanks for checking my series.. I gotta release the next episode.. Thx for the reminder.
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post #9 of 12 (permalink) Old 01-12-2020, 11:52 AM Thread Starter
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Duramax LMM Knocking Pt.5: Allison Installation & AMSOIL Fuel-Efficient ATF
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post #10 of 12 (permalink) Old 01-12-2020, 12:33 PM Thread Starter
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Duramax LMM Knocking Pt.6: Unplugging Injectors & AMSOIL Diesel Injector Clean
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