I have a question about transmission. I am bout to buy a 700R4 trans. The question i have is about the lockup torque converter. Do I have use a lockup TQ Converter are can I use the B&M 2500 Stall that I have. I have a 350 that is in pretty good shape should i just stick with that. I also want to know if it is possible the get 350 to run just as smooth as a 700R4?
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You can not use a TH350 Converter with a 700R4 transmission. I believe that is what you were asking. The only time you can use a TH350 converter with another transmission is the TH400 and you must have a dual bolt pattern flex plate and converter to swap back and forth if you wanted to. You do not have to use a lock-up with a 700R4 but it is suggested to decrease the heat in the transmission and increase fuel mileage.

The hub on a 350 torque convertor is 1.873" in diameter, and the 700R4 is 1.746" in diameter. Big difference, it wouldn't even try to fit the 700 pump bushing. You can run a non-lockup style torque convertor in a 700R4, but the transmission needs to be modified with a special lockup valve in the pump which will still allow proper cooling and lubrication.

I'm not sure what you are asking on your last question on if you can make a 350 as smooth as a 700R4. Are you asking about the shifts, engagments, or what?

what i am asking is i know that the 700R4 is a 4 speed and the 350 is a 3 speed. How can I get my 350 to shift as smooth and lighten the up on the 3 gears light a 700R4?