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Discussion Starter · #1 ·
I am having a 4R70W built and the builder will be giving me his second 8" custom converter. He says he can not reliably get a 10" converter to stall to 5000 or so and the 8" variant will be better and more consistent.

I am not a transmission guy and am posting this to get some feedback on possible problems with this solution.
 

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Discussion Starter · #5 ·
We have made a few of those, good for a NA setup. I would ask what he knows about the lock up, the 4R70 can lock up in WOT at the track. So you can take out a clutch fast if it is not strong enough.

Chris
Thanks,

Why is it basically a NA converter? I run a fogged but only spray a 125 hp shot.
My plan was to use the Baumann controller where I can specify a MPH for lockup if I even need to Lock it up on the track. I was thinking about a 5000rpm stall for the track but be able to lock up the converter for street driving using the two switchable program modes. Trying to have my cake and eat it too.
 

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Discussion Starter · #8 ·
Your motor requires a 5000 stall?
For street that lockup will be godsent. NA and small converters are great, robs less power. Use with a power adder like a turbo though, the torque would blow through it and the stall is too high for that kind of application. What rear gears are you running?

The New optishift from BE is pretty nice, but still requires too much tuning for me...MVB all the way :)
The thinking on the BE controller is to race in Drive in order to improve consistency. I am going from one extreme to the other having raced the manual for the last 8 years. After talking to the tran builder a little more we are going to try to build a 4500 converter. The car hits max touque at about 4700 rpm. I run 4.11 gears and a 28" tire. I launched the manual at 5500-6000 rpm but obviously have no torque multiplication. The programable controller will be nice for a street car, if it was a pure race car a manual valve body would be the choice.
 

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Discussion Starter · #10 ·
I am just checking back in on this thread to update how this 4R70W and 8" converter worked out. I have been extremely pleased with the performance of the 8" converter both on the street and the strip. I do not lock it up at the track and I have two different shift programs that I can swap out, one for street and one for race. I am able to race the car in drive and it shifts at 7500 RPM. I can cruise on the street with no problem and the converter locks up at highway speeds. I do spray this car off the hit with a 24 jet in a fogger. The converter flashed to about 4400 on motor and 5200 on spray. So far we have been able to 60' in the 1.32 as a best but it is regularly in the 1.35 area. I did bend all the vanes in the converter but luckily escaped with no other trans damage. The second converter was welded more and so far I have had no problems. Broader Performance in Wetherford, TX built the transmission and converter. He mentioned that if I wanted to race with the converter locked up he would have to install a different clutch in the converter. I am sure I am giving up some power with this big transmission but it sure is nice to drive on the street.
 
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