Cracked Flywheel
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Teching In
Joined: Feb 2005
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Cracked Flywheel I'm not sure if this should go under this form or engine but, here goes. I have a 2001 Yukon XL Denali. It has a 6.0L, 4L80E tranny and AWD transfer case. About two months ago it developed a clicking sound similar to valve clatter. I took it to my local mechanic who is a genius with GM trucks and upon further investigation it turned out to be a cracked flywheel. Thinking that this was an isolated incident, the flywheel was changed with an updated unit and I thought everything was fine. I moaned and groaned to GM about the problem but because it was off warranty no luck! Low and behold, about a month ago the noise reappeared. I have since changed the flywheel again.
Has anyone else had a similar problem with this engine/tranny combo? The cracks are concentrated from the crank bolt holes outward and toward one another. The only thing that the mechanic can see is a bit of additional movement in the crank in and out.
Hope someone can shed some light.
Has anyone else had a similar problem with this engine/tranny combo? The cracks are concentrated from the crank bolt holes outward and toward one another. The only thing that the mechanic can see is a bit of additional movement in the crank in and out.
Hope someone can shed some light.
The transmission in your truck is a 4L65-E. The torque converter can be causing it too. Are you running an aftermarket one? A converter that is out of balance or has an off-true welded hub on it could be the problem. Getting a bad stock one isn't unheard of either...
Thread Starter
Teching In
Joined: Feb 2005
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Thanks for the input guys! I'm pretty sure it is a 4L80E tranny. When it was apart for the first flywheel all the fluids were changed to synthetic in the tranny and the filter was changed. A hefty charge for a 4L80E tranny filter. The Denali seems to have a somewhat unique drivetrain. Even something as simple as a u-joint for the rear shaft stumped the jobbers - needed to get them right from GM using the VIN number.
There was nothing obvious about the torque converter when it was out. Everything seemed fine. Can't really tell with out measuring though.
What would make the crank drift with such force that it would crush the flywheel? Even with some fore and aft play, all the force within the engine is directed at turning the crank not forcing it back and forth.
The other thing that we looked for was some sort of casting imperfection that was preventing the engine and tranny housing from mating square to each other but, again nothing obvious.
There was nothing obvious about the torque converter when it was out. Everything seemed fine. Can't really tell with out measuring though.
What would make the crank drift with such force that it would crush the flywheel? Even with some fore and aft play, all the force within the engine is directed at turning the crank not forcing it back and forth.
The other thing that we looked for was some sort of casting imperfection that was preventing the engine and tranny housing from mating square to each other but, again nothing obvious.
Originally Posted by Jafobob1
The Denali seems to have a somewhat unique drivetrain....
Look for the code in the Glovebox.
M30=4L60-E
M32=4L65-E
MT1=4L80-E
Sorry to disappoint you.
