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Discussion Starter #1
I have a new carbed LS 408 combination that I put together that has <10 passes on it total so I'm trying to get the bugs worked out before next year. The engine runs very strong but I found that its going very lean the fuel pump isn't keeping up. Easy fix with a new fuel pump. The next problem is the trans/converter.

I have a th-350 with a reverse full manual valve body and t-brake that was build by a very reputable local shop. The converter is a circle D 230mm advertised to stall at 4800-5000rpm. The converter was brand new and the th-350 was build about 3 years ago and probably has 30-40 passes on it and a few hundred street miles. The engine seems to like to be shifted between 7000-7200rpm.

The rpm drop between shifts seems pretty good.
1st gear shift at 7020RPM drops to 6430RPM in 2nd
2nd gear shift at 7020RPM drops to 6320 in 3rd
My time slip shows me trapping at 125.97mph @ 7500RPM


I'm concerned about the slippage I'm seeing if I'm doing the calculation correctly. I'm not sure if its a trans problem or converter problem or both. I used the calculator in the following link for the calculation.
http://www.wallaceracing.com/converter-slip.php

mph 125.97
rpm 7500
gear 4.33
circumference 89.25 (measured)
slippage = 13.99%

At the request of the converter builder I turned my 2 step rev limiter way up to see what the actual stall is. It went to 5600rpm for a split sec then the car rolled forward and the t-brake would not hold it. Its always held in the past but I've always had the 2 step set at a lower rpm 2500-3000rpm. Possible trans problem?

Let me know what you guys think? Sorry for the long post but I want to get all the info needed in there.
 

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It appears as though the converter is a little loose at 17%. Its showing the true stall speed on the gear change which is between 6300 and 6400 rpm. If you plan on shifting at 7000 , a 5500-5700 stall converter would be a better choice.


Hutch
 

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Discussion Starter #3
Thanks for the reply. Any idea why the t-brake didn't hold at high rpm? I was wondering if you should plan on a trans rebuild this winter or stick with it. And if I rebuild it anyway would I be better off to go with a th-400? I've already got the csr shield on my th-350 and the trans x-member set up for a th-350 which makes me hesitate to change transmissions but I will if needed.
 

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Not sure why it started moving on the transbrake. It could be low pressure on the brake but if you don't leave higher than 3800 or so it will never be a problem. Depending on what you have in mind for the future will tell whether a trans change is required.


Hutch
 
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