Thread: th350 to 700r4 swap

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can I still use my th350 flywheel if it is 168 tooth? I know I cant use my th350 stall converter or can I? also I`m am confused about the lock up.The trans came out of a 91 astro van if I have to buy a new converter should I get one with lock up or non lock up?

done one 700r4 project on a 283. the flywheel shouldn't be a problem, not for sure about using the 350 converter though. our tranny man said the lock up is for when in overdrive the tranny doesn't get hot, it lets fluid flow in a way to prevent this during overdrive. Never discussed using non lock ups with anyone. If you have a mild set up I'm sure the stock 700 converter would do fine, depending on what you want for stall speed, or how many pony's your planning to have. Our tranny was an '86 out of a truck to which you can run a 12 volt wire to the proper terminal to make work correctly,(powered when ign. swith is on.) But some spot in time I think the 700 went to you had to have a stand alone computer to run them. Our tranny worked great on our project. Make sure you get the cable to the carb adjusted correctly. Make sure they didn't change the bell housing bolt pattern. (I don't think they did in 91?)

You don't need a computer for a 700R4. Just the correct wiring to the overdrive terminal. Also, don't even consider a non-lockup. You'll fry it. They only lock up in overdrive unless you wire in a switch to manually lock it.

you can not use a 350 converter the 700 is 17/8 inches longer than a short shaft 350 also the mount holes are 17/8 inches longer you have to move your crossmenber and shorten your drive shaft.
the tv cable runs your shifts you have to use it adjust it so there is no slack at full throtle If you drop the pan you will see 2 wires going to the tcc solenoid one side has a + the other a - this is at the front of the pan, near the back is a one wire switch on you 91 trans this is 4th gear .cut and splice a terminal to the - wire on the solenoid to the 4th gear switch then run 12 volts to the a terminal on the out side of the trans this is the front outer conector.This is what those $100 kits do go luck

thanks for all you guys help I have not done the swap yet but i wanted to get my ducks in a row before i just jump in to it.

You could make it even easier and go with a 200R4.The trans is the same length and uses the same yoke as the turbo 350.I ran one behind a 400hp SBC for years with no problems at all.

1lowryd, Keep in mind that the 700 R4 was designed for the 3:73 and 4:11 rears. The TH350 runs best with 3:42 or better. With a TH350 and 3:73 rear you'll be turning 3000 RPM @60 MPH. With a 700 and 3:73 rear you'll turn 2600 @ 65MPH. If you can marry that 700 to a 3:42 or better, then you'll be looking at higher cruising speed with lower RPM's. The end result is that you won't get your neck snapped on take off, better fuel economy, better highway cruising speeds, and you'll have the available RPM's for on ramps and passing. Something to think about.