I purchased a Th400 and a 4500 stall converter at the begining of last season, only to have it come apart yesterday during a double points race...
I had maybe 50 passes on it behind a 400-450hp SBC... it should have lasted forever... attached is a picture of what I found in the pan... I'm not a transmission person, but from what I've found out they are the parts of the case that were suppose to retain a snap ring that holds the clutch pack in place... tell me what you think would have caused this to happen...

thanks

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I little more info...
I made 3 qualifing passes and went four rounds in eliminations the day before... only thing out of the ordinary was that on the last pass my trans temp went higher than normal... over 200... but trans seemed to still work. drove back to pits and sat until the next day... next day seemed fine pulling up to make first pass for time trials... burn out was off, thought my posi was slipping again... pulled up and took the green... lauched seemed ok but shifting to second sent the tach sailing...

Temp went up because the clutches were slipping when the snap ring broke/came out. Have you pulled it apart yet to see what went first.

planning on pulling it tomorrow... called the company/guy that built it for me today, but he has yet to get back to me... suppose to have a year warranty so hopefully he will stand behind it... otherwise I will have it looked at locally... I'm hoping that the damage is limited to the case... and it can be put back together without alot of $$$...

why would this part of the case fail?? My little ole 355 should not have been able to caused this damage... could it have been a bad case??

trying to have some background before he calls me....

Common failure in a t-400 case since GM introduced them.

hopefully your builder had a wide snap ring in it.

I suggest use of the waved cushion steel plate in all t-400 intermediate clutch pack setups.

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If you can't fix it with a hammer, you have an electrical problem.

Crosley suggest the waved steel plate because the trans needs the absorption[usually high line pressure on racing trans]. Not a bad idea in the direct drum, as well.

The most torque this trans will see may be during the 1-2 upshift.

A wide snap ring from a 727,chrysler trans, [forward clutch drum], will, most times, mitagate the severe stress that is exerted on the case during the 1-2 upshift.

I doubt this was done and the result will be a ruined case.