350 turbo torque converter by pass switch

Are you referring to the lockup circuit? I will guess you are trying to keep the lockup feature without a computer. It's complicated if you want to make it automatic. The simplest circuit uses a pressure switch to sense the trans has gone into 3rd (TH350C) or 4th (200-4R/700-R4) gear, and a brake pedal switch to unlock when you slow down. You can add a vacuum switch (expensive) to unlock when you step on the gas, or you can use a switch on the dash or old-school highbeam switch on the floor to unlock it yourself when you downshift.

ssn696 said:

You can add a vacuum switch (expensive) to unlock when you step on the gas, or you can use a switch on the dash or old-school highbeam switch on the floor to unlock it yourself when you downshift.

Click to expand...

i like adding the vacuum switch. depending on the rear gear ratio, it helps me from lugging the engine on slight up hill grades. i find them on early 80's chevy trucks and vans. they're mounted on the firewall.

Here's the original thread:
https://gbodyforum.com/threads/200-4r-tc-lockup-kit-build-your-own.58098/#post-490669