Flex plate crack

[mjolinar]

I have a 78' 1/2 ton 4x4 with a TH350 behind a 92' small block. My problem is that I have cracked 3 flex plates one of which the entire center section was broken out, and dont know why. Anyone know what could be causing this. The transmission shifts very hard and I am wondering if that could be the cause.

Any help is appreciated.

[Lt.Del]

Just throwing a few things out here...
Are you using the same torque converter?  Could it be warped?  They aren't expensive, next time you gotta replace the flex plate, replace the converter just to rule it out if anything else.

Now, the flex plate attaches to the end of the crank.  Have you noticed any balancing problems (ie: vibrations in engine at higher rpms)?  The crank could be warped/bent.

Are you overtightening the flex plate bolts?  They don't have to be too tight to function correctly.

One other factor that is relative: the starter.  Any grinding noises from the starter/flex plate when trying to start the engine??

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4

[mjolinar]

I will check the torque converter that is a good possibility. I  Havent replaced anything yet.The starter is working perfectly, which is unusual for a chevy. Also, the flex plate crank bolts were torqued per Haynes manual. I even bought the high performance TCI flex plate this time. The only vibrations I get are at around 75 mph or 3000 rpm, but I believe that is just from slop from wear in the shaft coupler.

[Pushrod]

Did the engine come out of a standard shift vehicle? Maybe a pilot bearing is the issue here??

[roundedline]

Pilot Bearing wouldn't be an issue since the Converter doesn't seat in the crank like a input shaft of a manual does.

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[mjolinar]

It seems to be the dowel pins are worn out and they were causing misalignment.