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Bent Flexplate?

I have a 1969 Mach I mustang with a 1968 390 FE motor 4bbl (original 428cj). I just installed this motor back in May 2009. The transmission was not replaced. My problem is I have a slight scraping sound inside the transmission bell housing. This ocurred after I filled the transmission with fluid. I think the flex plate is bent. I shimmed the starter but this did not work. Is there any way that I can figure this problem out without removing the transmission and replacing the flex plate?

With the car on a lift, remove the bell-housing dust cover so you can SEE the flex plate and observe it’s rotation with the engine running…

“Neutral Drops” (you wouldn’t be doing smoke shows would you?) have been known to twist the centers out of flex-plates…

The flex plate could also be bent because of any wrestling matches trying to install the motor or if the torque converter was not fully seated when the engine was installed.
If the converter was not seated on the splines all of the way then tightening the torque converter bolts could have distorted the flex plate. Eventually the converter may seat but the flex plate could still be bent.

It was a bad torque converter (I Think). I removed the trans over labor day weekend. I looked at the flex plate and initially thought it was bent. I took it off and found out it was not bent. I installed a new torque converter and a rebuilt transmission and every thing is fine. What I think happened last year was when I installed the rebuilt motor I only put 2 quarts of trans fluid in the trans. On initial start-up I think I ruined the torque converter. This time I put 8 quarts in the rebuilt trans started it up and put in 2 more.

other things to consider: the middle stub of the torque convert must fit into the back of the crank shaft. — Check how the flex plate fits on the TQ before installation – internal and external balance of the engine.

the original 428cj was internally balance so the flex plate had no weight attached to it. I installed a rebuilt engine and I do nit know how it was balanced, the flexplate that came with the rebuilt motor had a weight on it . I replaced it with no weight on it.