Strange noise...

[pontiacgp]

What would cause that? sh*ts crazy

Cheap flexplate, a good aftermarket one won't crack

 

[MrSony]

Even if it isn't the flexplate, if it is a stocker or a no name, get rid of it. Things that spin, don't cheap out on.

 

[565bbchevy]

If the torque converter bolts are incorrect they could bottom out before being fully tightened and make a lower engine knocking noise.

 

[oldsmobile joe]

excessive crankshaft end play can contribute to a cracked flex plate.
joe

 

[SoFloG]

I've got new grade 8 nuts and thru bolts.on the converter with washers and lock washers between. The converter and flywheel are definitely 1 with each other. I'm thinking I may have spaced the tc too much not allowing for rearward deflection, and maybe that cracked the flywheel?? I have yet to confirm this though, got too cold and too late to mess with the car, so tomorrow hopefully.

 

[SoFloG]

Even if it isn't the flexplate, if it is a stocker or a no name, get rid of it. Things that spin, don't cheap out on.

I agree, I don't cheap out on anything especially any component that moves.

 

[Pontiac455]

If the flywheel were cracked you would notice the noise while starting the vehicle hence the torque being applied fromtthe starter turning over the engine. The flywheel wouldn't survive several 6000 rpm pulls before s-ing the bed. Check the bolts like 565 says.

 

[Wraith]

I've had the opportunity to see three cracked flexplates, all new OE Chevrolet, all brand new crate engines, two ZZ4's and one 290hp. All of them presented noises while idling or light load, starting or under power they would lock up the crack and you would hear nothing, all at/around 8K miles. All three were replaced with new SFI flywheels plus grade 8 hardware and never had a problem again.

 

[SoFloG]

Bolts are not the issue, I have through bolts with nuts. There are no wear marks anywhere on anything.

 

[Wraith]

I know it sucks but I'd pull the transmission and look at the converter, when I did mine the crack was barely visible but made sounds randomly. I'd have never guessed it if my buddy hadn't just went through the same thing. You could try hitting the flywheel with a hammer first, it should ring true if good, kind of like a tuning fork, would be off if cracked.