We have a 72 Pontiac Lemans with a stroked engine putting out 650 HP and 725 TQ. Street/strip car. We did some blasts on a deserted road to seat the rings in the engine. Car pulled hard in every gear and trans worked fine. We rebuilt the trans same time as engine. It worked perfectly fine during the blasts. On the way home the car would want to lock up in third gear.
We pulled the pan and found small pieces of metal that looked like the springs in a roller clutch/sprag. Took it apart and sure enough the intermediate roller was destroyed. It was the stock 8 element roller.
Trans has an ATI stock rebuild kit #406330. Turbo-Action reverse manual valve body #24141. PTC 5000 stall converter.
Here are some pics:
Stock intermediate roller clutch.
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The inner race of the roller clutch.
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Case of the TH400
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Clutches and steels look good.
Oil is blackened, not sure why. Maybe from breaking in???
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Thinking of using this sprag. It is a 34 element peice, #34652A
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What are your thoughts on how we should progress on this TH400 transmission.


Thanks.

Anybody?

You really want an early 400 drum that uses the sprag instead of the roller clutch. Use the 34 element instead of the 16. Make sure when you change drums that either the drum or the piston has a checkball, you don't want to run it without at least one of them having that.

Thanks for the reply.
Where on the drum is the checkball, can it be seen or heard?
Where on the piston will the checkball be?
Would it be OK for both to have a checkball?

Whether it has a ball in the piston or drum, it can be seen. Only the aluminum pistons MAY have a ball, the molded or steel pistons do not. The drums, just look, you will see it if it is there. If both have a ball, not a big deal.