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I've been running a th350 in my girlfriend's pure stock this season and I've already gone through two of them. I know the first one didn't have the torque converter seated in the front pump good enough and the second one was living on borrowed time anyway. My question is how can I build a good th350 for circle track racing that will hold up? It's bolted to a bone stock 4.8 ls motor at the moment. Does being at an angle around the corners matter? Will it still work the same way, or is it more akin to the motor where you can potentially starve the pickup by cornering at speed? The car is set up for a three speed transmission and I have two cases to build. I don't want to change setup (gearing, powerglide), and I already have the th350s that need rebuilt, so I'm not going to toss them out just to buy a different transmission
 

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1979 Chevrolet Malibu 496-TH400-9" (cruiser). 1992 Chevrolet S10 355-700r4-7.625" (daily driver).
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Hopefully some of the circle track folks can chime in on the effect of cornering at speed. I'm limited to street/strip and daily drivers. I'm thinking the passenger side of the TH350 case would act as a pretty good "baffle" of sorts. Given the full mark being the surface where the pan bolts on, there isn't much space for fluid to really climb. I can't think fluid would climb the dipstick tube that far. If you wanted to build something into the pan on the passenger side that could help keep more fluid in the pan. I'm curious to hear what others think or what they do.

How much shifting happens and what gears are being used? I've spoken to people that stay in one gear going around the track.

Do you have a gauge for transmission temperature and a good cooler? If it runs too hot all the time, the longevity won't be there no matter what you build. If you are keeping it cool, the TH350 is plenty capable of that power level.

You mentioned a little about both failed units. How did the unit that was "on borrowed time" fail? Are you burning clutches or breaking hard parts? Were these stock builds or were these built along the way?

How competitive is all of this? Obviously more money spent can yield better performance. If this is more about having fun, wanting to finish races and trying to minimize expenses I think you could stay pretty basic here.

I'm a shade tree mechanic and a hobbyist. I'm not a real transmission guy, but I tinker with a few here and there. I joined this forum about 6 months ago and someone shared this link. This is great stuff from professionals.

 

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You need to buy or build a circle track competition level TH350. The converter needs to be of a stall that matches the cam and it really needs to be of the type with furnace brazed elements. There are converters sold specific to the circle track application.

The Crankcase Collition link that 1979Malibu linked is a good source for the builder. As far as pans go the usual change is a deep sump with matching deep pickup. This is good at just keeping enough oil over the pickup that it doesn’t suck air in the turns. In a left turns normal rotation being clockwise as viewed from the front oil that stacks up on the right side of the case gets into the rotating elements where it is thrown over the top of these elements back into the pan on the left side so there is compensation for the turn dynamics forcing oil to the right.

Bogie
 
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