Heres one that might stump you.

[tactransman]

tactransman
 do you  believe the flexplate is failing because when it makes contact with the part of the pump housing that sticks out it putting  uneven pressure on the flexplate or  because the flexplate is "flexing" back and forth too much.

 How much does a converter travel back and forth normally?

Yes,the flexplate is not being allowed to spin flat and it is flexing it as it goes around.
What do you mean by converter travel? You should have to pull the converter up to the flex plate about 1/4 of an inch with everything bolted together(engine and trans.)

Here is a pic that helps explain about the converter to flex plate gap.

[hemitodd]

what i meant by coverter travel was when everything is bolted up and you pull the converter 1/4" ahead to bolt it to the flexplate,  doesn't that mean that when the motor is then running the plate is flexing a 1/4" in order for the back of the converter to run into the front of the pump? and isnt that too much for it to handle.

why is it flexig so much as to be coming in contact with it?

[tactransman]

If you have a 1/4 inch gap from the flexplate to the converter pads,it should not be hitting the pump. Is your crankshaft end play OK?

[ShelbyDogg]

When I raced, I always had to grind the front pump, right where you marked your picture. I just used an angle grinder on it and took off as much as I could.

That cracked flexplate could also me from an unbalanced engine.  My first challenger had a 440 ini t that was built by Jasper around 1975. It had 6-pack rods in it without 6-pack anything else.  It always vibrated above idle but being 17, I drove it anyway. Jumping on it one day, it vibrated so bad that the tailshaft broke off at the rear bearing, throwing fluid all over the exhaust.  Do you know anything about your engine?

[MyMopar]

If all the solutions check out, could it be that he bought a low quality flex plate?

[tactransman]

It looks like the heavier duty Mopar Performance flexplate.

[ntstlgl1970]

If it was hitting the pump wouldn't it make a hellacious racket when it was running too? I agree that the crank end play should be checked and also the line pressure on the trans (if too high can take out the thrust bearing in the engine) I also wonder about the converter being balloned...there was a thread a long time back that had pics of a ballooned converter (or maybe the mounting pad face of the converter that was ballooned out)

[Moparal]

Can you get more pics like side view and both sides of the plate?

[hemitodd]

I didnt have a 1/4" ( i used that because you used that as an example) i had about 1/8.

i will check crank endplay when i get a chance( working 60 hour weeks at the nuclear plant right now but hopefully i get a chance tommorrow).

no vibration in the in the motor seems really smooth.

i dont get the vibration until about 3000rpm.

if it was from too high a line pressure how would i check for that and whats considered too high

it is a mopar performance plate, i just installed a B&M flexplate does seem better

if i did grind the pump how deep can you go, how thick it the metal there?

again thanks for the help

[71chally416]

I seem to remember it being 1/8". Don't seem like less than that would make much difference. You should be able to clearly see where it's been hitting. Just be careful you cover the input shaft on the tranny and tape up the pump hole so it don't get grinding crap in it.

Did you check the fit of the hub into the crank hole? It can't have slop or it'll wobble in the hole under power. It's best to measure both the hole and the hub with calipers.   

[JS27N0B]

Did you check the fit of the hub into the crank hole? It can't have slop or it'll wobble in the hole under power. It's best to measure both the hole and the hub with calipers.  

I'm still waiting for this answer as well.

[ntstlgl1970]

I didnt have a 1/4" ( i used that because you used that as an example) i had about 1/8.

i will check crank endplay when i get a chance( working 60 hour weeks at the nuclear plant right now but hopefully i get a chance tommorrow).

no vibration in the in the motor seems really smooth.

i dont get the vibration until about 3000rpm.

if it was from too high a line pressure how would i check for that and whats considered too high

it is a mopar performance plate, i just installed a B&M flexplate does seem better

if i did grind the pump how deep can you go, how thick it the metal there?

again thanks for the help

Sorry, I'll clarify if the thrust bearing is bad in the engine, one thing to check is the trans line pressure to see if it is too high...

[hemitodd]

"Did you check the fit of the hub into the crank hole? It can't have slop or it'll wobble in the hole under power. It's best to measure both the hole and the hub with calipers."

sorry for not understanding but do you mean the "hub" on the front of the converter, the part i circled on the pic below(just found that pic on the web). if so i've never checked to see how it fits in the back of the crankshaft, i never knew it was important.

[71chally416]

That would be the part that pilots into the crankshaft hole 

Just looking to eliminate any possibility the person that machined it did it right. It cannot have slop in that hole.

[hemitodd]

thanks for the clarification,

im hoping that by tommorrow or i guess tonight(im at work on nightshift) i will have dropped the transmission and take pictures and measurements of everything and see what you guys think.

stay tuned.........