Strange noise...

[64nailhead]

That is bizarre! I have a Trailblazer SS with an LS2 6.0 After I converted to a 4L80E, I've gone through 3 flexplates in 3 years (over 90K miles). First one was a strong TCI (SFI rated) that cracked along all three converter mounting points. The other 2 were stock flexplates and did the 360 crack around the crank mounting point.

It's driving my Transmission guy crazy. He's checked everything trans related and can't find an issue there. I didn't think about the crankshaft end play as a possible culprit. I'll be watching this thread as everything unfolds.

Hutch

The bolt hole failure I've only seen when the bolts aren't tight enough. The center breaking is generally something else - TC swelling, crankshaft end play or too much torque for the flexplate. I would like to see all 3, especially the one with the bolt failure to see if there is any evidence of it showing issues at the crank bolt hole area.

 

[Turbolq4]

I had a 69 GTO with an angry 400 in it. It twisted the center out of it's flexplate. Wished I would have taken pictures but didn't.

 

[SoFloG]

Well... months later I discovered the problem today. It was ever slightly running on the starter gear, no visible wear marks, and the bendix is fully retracting. While under there I touched the starter gear with my knife and the noise left. We're talking like .5mm. I loosened the bolts on the starter and retorqued them with a cont hair of extra clearance and it seems to have done the trick. The starter has slight in/out play on the gear so even though it was retracted, the gear would slip out and make this miniscule contact with the flywheel. I'm just glad I don' have to yank the trans.

 

[Opie Knievel]

I'm just glad I don' have to yank the trans.

Good news indeed! I'm glad you got the problem fixed.

 

[SoFloG]

Thanks guys, I'm gonna shim it as well,but at least now I can focus on my head swap.