Flexing a Flex Plate?

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Below are the pictures of my crank and TC after about 4 months and 1500 miles. The snout of the TC was tight in the crank when I put it together (didn't know better always a stick guy before). Had the proper clearance between the TC pads and flex plate before pulling it forward. Noticed the crank walking one day and found I had about 0.032 crank movement and a wiped thrust bearing.

Good info on TC dimensions and clearances, surprisingly little out there about this.
Torque Converter info for various transmissions





Crank.jpg
Torque Converter.jpg
 
It looks like lots of folks have this same B&M flex plate lying around loose. Can someone put a straightedge across the back of their flexplate and let me know if theirs is in fact perfectly flat?

As per my post #10 above, the "flat" section of my flex plate is a little bit concave from the engine side although I can't put a straightedge on the back with it bolted to the crank.

I didn't check for perfect flatness when I originally installed it, and am wondering if my flex plate is somehow to blame for this poor fit now??

Covering all the bases. Thanks.

Mine was perfectly flat.
 
Below are the pictures of my crank and TC after about 4 months and 1500 miles. The snout of the TC was tight in the crank when I put it together (didn't know better always a stick guy before). Had the proper clearance between the TC pads and flex plate before pulling it forward. Noticed the crank walking one day and found I had about 0.032 crank movement and a wiped thrust bearing.

Good info on TC dimensions and clearances, surprisingly little out there about this.
Torque Converter info for various transmissions



View attachment 1715465635

View attachment 1715465635 View attachment 1715465636

Ouch! Kim
 
You guys might find this interesting:

While I have been talking with Hughes today about possibly shipping the TC back to them, I also put in a call to B&M (Holley Group) to ask them a few questions about the flatness of the Flex Plate etc. While I do not have plans of doing this, here is what I was told:

"There is not a set tolerance on flexplates. It can vary from 1/8” up to ¼” when they are setting flat and not bolted to anything. Bolting to a converter and crankshaft is what straightens them up"

NOT part of my plan, but interesting enough to share.
 
You guys might find this interesting:

While I have been talking with Hughes today about possibly shipping the TC back to them, I also put in a call to B&M (Holley Group) to ask them a few questions about the flatness of the Flex Plate etc. While I do not have plans of doing this, here is what I was told:

"There is not a set tolerance on flexplates. It can vary from 1/8” up to ¼” when they are setting flat and not bolted to anything. Bolting to a converter and crankshaft is what straightens them up"

NOT part of my plan, but interesting enough to share.

Yep, I found the same thing in my endless search for information on what went wrong. I was worried about mine since I had to pry it apart, but thankfully it stayed straight.
 
I didn't do that this time around, because I am replacing with the same* TC so figured a smooth swap. Originally, I did have to slightly egg out a couple of the holes for the after market "production variances". Having the flex plate bolted to the crank and the TC pilot hub engaged in the back of the crank is the only way I can think of (with my cardboard and PlayDoh) to ensure that both pieces are concentric before starting to massage bolt holes.

*almost the same
I’d also be worried about how the centerline of the converter as mounted to the crank lines up with the trans centerline, the pump bushing won’t like anything being off as I believe that is mentioned in the B&M paperwork. Think rapid bushing wear and leakage. Line boring of the block changes alignment, and while an oem flexplate actually flexes and is more forgiving the B&M doesn’t and isn’t. Pretty damn rigid as I’m sure you’ve noticed. Have you checked crank pilot depth, and the converters pilot? Difference in positioning from block/trans mounting surface of the oem plate vs. the B&M? Likely some hardened sae washers (Hillman brand at better hardware stores) is all you’ll need but lots to check over.
 
I’d also be worried about how the centerline of the converter as mounted to the crank lines up with the trans centerline, the pump bushing won’t like anything being off as I believe that is mentioned in the B&M paperwork. Think rapid bushing wear and leakage. Line boring of the block changes alignment, and while an oem flexplate actually flexes and is more forgiving the B&M doesn’t and isn’t. Pretty damn rigid as I’m sure you’ve noticed. Have you checked crank pilot depth, and the converters pilot? Difference in positioning from block/trans mounting surface of the oem plate vs. the B&M? Likely some hardened sae washers (Hillman brand at better hardware stores) is all you’ll need but lots to check over.


When you look at the B&M you would think it doesn't flex (I know I did), but it actually does. How much, I can't say, however after my second go around I found marks that showed movement.

Agree with the alignment and currently making sure that the snout is aligned with the center of the crank so there is no pressure points.

I guess the point I'm trying to make is that the TQ needs to be able to slide inside the crank to allow for fluctuations in tranny pressure surges and that the flex plate flexes.
 
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