lvhdude

Hello, New to the forum so apologies if my queries are redundant. I am working on a new to me 55 chevy with a 265 backed by a TH350C. These are new to me, and I'm told I can run them without worrying about the lockup function, and have read that they have more converter slip. I have read that they worked with a vacuume switch to unlock the converter under load, and a brake switch to unlock when the brakes are applied, and they ran through a neutral safety switch for, well I don't know. Now that I'm dizzy from conflicting info, here's some questions. 1) Why would I want it to unlock if I'm on the brakes? Seems like engine braking would be better locked up. 2) Why the neutral safety switch? If it's in neutral or park what's the issue? 3) Does the trans put pressure to the lockup clutch only in 3rd gear? So I would not have to worry about how it works in 1st and 2nd? Or is it applied in all 3 gears? My thinking is power to the lockup solenoid through a vacuume switch that will unlock at what ever GM thinks it should, 10" of vacuume or so, and maybe a toggle switch if I want to turn the function off. Like if I'm really flogging that high torque 265. Yes I realize there are some kits to basically disable the function, but I kinda like the idea at cruise. No it wouldn't be my first choice of a trans to swap in. Yes down the road it will get re-powered and a true OD trans, but for now I'm kinda working with what I've got. Thanks in advance for advice from those who know these gearboxes.

tayto

all GM lockup transmission of that era use a brake switch and vacuum switch to control lockup. i believe one of the reasons for the brake switch is so the vehicle wont stall when coming to a stop with converter locked.. personally I don't like these transmissions that don't use ECU control. With a computer lockup is setup to engage a certain speeds. I daily drove a car for 5 years that locked up immediately upon shifting to 4th, it just sucks IMO. I think TCI makes a kit to control lockup with a speed sensor but it is expensive.

all automatics should have a neutral safety switch, but it doesn't have anything to do with lockup.