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Nailing down a broken flywheel
Posted to Technical Tips Forum on 9/19/2013 24 Replies

Up until a couple of weeks ago we had never replaced or had any problems with broken flywheels on the newer, to us, Gm full size pickups.

A customer came to us with 04 2500 HD 6.0 with a 4l80e trans. The complaint was a tick in the motor. When I first heard it sounded like a lifter ticking away. Under the hood though I could not isolate the noise to the top of the motor and noted it was best heard behind the frt. tire in the wheel well.

I also noted that the noise did not leave when dropped into gear but when you power braked it did go way at about 1200 rpm. With it in neutral the noise was still clear at 1500 rpm.

When we got into the shop the noise went away. The customer was good enough to understand and took it home. He reported the noise would come and go at will. Last I had talked to him it had not bothered for two weeks.

I did note a bulletin about flywheels cracking. A peek on iATN showed up some reports of them breaking also.

Enter truck number two, a 05 Tahoe with the 5.3 and smaller auto trans. Again,exact same noise, same effect when power loading it and this one did not go away. A stethoscope picked the noise up best between the starter and the block clear to the back. In the shop we pulled the little round inspection cover off the lower bell housing and with a good light were able to see a crack.

We replaced the flywheel, which was cracked clear around the bolt pattern and when done I called the other customer and told him I was now positive we had a cracked flywheel. He got it right in and we replaced it also.

It is interesting to note that although both trucks sounded and acted exactly the same they have different engines, different transmissions and different part number flywheels. Also the service bulletin only applied to the 3/4 ton, not the Tahoe.

And the news you can use? Sounds like a lifter, maybe a bit faster, hear it behind the frt. tires. In the air with a stethoscope you pick it very strongly between the starter and the engine block.

FWIW we used new GM parts, the new flywheel was slightly different, also used new bolts, they came with a locking agent on them, and the spacer.

Roy from Iowa

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car Vehicle Data

2005 Chevrolet Tahoe LS 5.3L

Engine5.3 L
Trans4-speed Automatic (Electronic)