HELP!!! flex plate hitting dust cover

[achevy1978]

hi all,
i replaced my th400 and when i started it i got a horrible sound scared me..
it was i'm assuming the flex plate hitting the dust shield... so i ground down where the scraping was
and it was okay in park but when ii put it in gear its back even worse....why

[bd]

A few possibilities...

• You may have installed the dust shield incorrectly, so it drags the front of the flexplate.  Remove the flexplate to see if the noise disappears.
  
  
• Did you replace the converter bolts with taller bolts (thicker heads)?
  
  
• You may have a cracked flexplate.
  
  
• You may have insufficient clearance between the converter and front pump.  You should have noticed about an inch gap or a little more between the converter and flexplate before bolting them together.
  
  
• You may have excessive endplay on the crankshaft allowing the flexplate & converter to walk fore and aft.

[achevy1978]

didnt replace bolts , newer flex plate,converter seemed fine . i'll get uner with a scew driver and see iff there is play in crank.but new bearings were put in ....may try to find a plastic one but i wont be able to use the torque arms

thanks

[bd]

Any chance something got trapped in the bell area, or something unnoticed wasn't removed that should have been, before the trans was stabbed?  When was the crank thrust replaced?  Could the flexplate be backwards?  If all you did was replace the trans, all other things being equal, you shouldn't have to substitute a different dust cover casting.  So, what changed?  Does the noise disappear when you remove the dust cover?

[achevy1978]

yea when i take it off the noise is gone... thrust was done with rebuild no excessive play that i remember

[bd]

Good!  Are there telltale 'grind' marks on the cover?  What was hitting?

[achevy1978]

there were but i couldn't tell what was hitting. i figured a balance weight on flex plate but didn't see anything...so i ground out the cover and got it to stop in park but when in gear its bad.....i don't get it

[bd]

That's why I asked about crankshaft end play.  The rotating assembly with flexplate/converter may be thrusting forward.  You really should check the end play on the crank using a dial indicator - should measure 0.002" - 0.006" on a small block, 0.006" - 0.010" on a big block.  A cracked flexplate can allow relative movement between the converter and crank flange, as well.  Did you by any chance remove the flexplate while the transmission was out?

With the dust shield removed, drive axle(s) supported on jack stands, and the drive wheels safely off the ground, have an assistant start the engine and shift the trans from park into gear as you watch the converter to see if it noticeably shifts forward.  Keep your clothes, hair, body, tools, etc. a safe distance from the flexplate and converter while the engine is running.  Be mindful of 'hot' exhaust components.

[achevy1978]

no flex plate is fairly new...i tried to crank but didn't see any noticeable movement...