Need some schooling on flex plates

[b5blue]

How can that skinny hunk of steel do what it does and why would it need to flex? Flex plates seem way too flimsy for there job...I mean we chain/bolt/strap our engines down to hold all that power. Everything else on our mighty Mopars is MASSIVE yet it all runs through a piece of sheetmetal not much bigger than a hubcap? Whats up with that? Which one would you recommend for my 440/727?  I'll be pulling the tranny soon for a streetabilty rebuild and new 145K converter...good time to up grade from bone-stock one?

[Cooter]

By that reasoning, look at the driveshaft and what it does.....I mean, let's face it, it is nothing more than a piece of exhaust tubing that has to put at least 600 Ft. Lbs. of torque down to the road, with u-joints on each end...The Flex plate doesn't have to be huge as it is not like a Clutch and flywheel here...This is why Stall converters don't perform like every average "Joe" thinks they do and rev up and slam into gear...If they did, then you would be correct...As it is, they only drive a fluid coupling which is much softer on it than a clutch...

[skip68]

One thing to keep in mind is when you change the stall converter, the flex plate may not work.   You may need to buy another flex plate that matches the bolt pattern of the new converter.       I know what you mean though.   When I did mine I was shocked that the flex plate was so weak looking.   

[b5blue]

It's not a matter of how hard 450lb of torque or 400 horsepower is applied it's that it still transfers through that plate (to me) and what aspect is flexing. I do not think drive shafts are at best 14 gauge exhaust tubing, that's a bit overboard and counter to the topic, have you got a hangover Cooter?  I have a Mopar 145K going in and a forged crank 440 I do need to check for 5/16th or 7/16th converter bolts. SFI plates are at least a full disk but I'm not getting what or why "flex"?

[Just 6T9 CHGR]

I run the B & M flexplate....much more beefy than the stocker...




This happened on my old engine.....dont know how

[b5blue]

THAT is my concern exactly! 

[Ghoste]

It isn't flexing rotationally, it flexes back and forth between the rear of the engine and front of the transmission.  When your torque converter is turning, keep in mind that is like two fans in there facing each other.  The fluid being flung from one fan against the other has the effect of trying to not only force the receiving fan to turn but also force both fans away from each other.  The flexplate allows for this action of the torque converter to be trying to force the engine and trans components away from each other.  This an awkwardly worded oversimplification but I hope it makes some sense of it for you.

[b5blue]

It's a darn good start.....I think.....so my TC slides in and out a little on the input shaft. 

[John_Kunkel]

The flexplate can be so thin because the majority of the load it sees is shear load.

[Cooter]

If your engine is set up and balanced properly, I wouldn't think you'd need any stronger flex plate..I've been puttin' over 650 HP through a stock Flex Plate and it's fine..I say that and it could break tomorrow, but most of the time when the plate breaks it's from Harmonic vibrations, not so much as from torque...BTW: If you've ever cut a driveshaft into, you'd see just how "thick" it really is...