Th200 lockup?

[fly_25]

How do I know if I have a lockup transmission? Ever since I had the car the lockup never worked so I'm curious if this car even has a lockup. It's an 85 cutlass. i know the vacuum switch is supposed to lock the transmission but the transmission plug only has one green wire

 

[ssn696]

That looks like a non-computer lockup setup. When you stomp on the gas, the vacuum switch senses lower vacuum when the carb opens up, breaking the circuit, enabling the torque converter to unlock let to the transmission downshift.

The four-pin plug goes into the transmission. There should be a switched connection on the brake pedal, separate from the brake light switch, that also unlocks if the brakes are applied.

If you eliminate the lockup, don't discard the wire harness and vacuum switch...that's useful for those of us wanting to use a 200-4R or 700-R4 without a computer.

 

[ELCAM]

If the transmission has the 4 pin connector on it it is a lockup unit.

This is a homemade lock up system , your car would have the computer controlling the lockup from the factory and would not have used the vacuum switch.

The one wire on the connector is all you will need but you will have to change the wiring on the valve body. The computer wiring will not be setup to use just one wire.

You need to pull the pan, make sure the green wire goes to the positive side of the TCC solenoid (might be correct as is but best to check) The difference will be the computer used to ground the solenoid with a wire in that connector, you will need to change it so the ground goes through the 3rd gear pressure switch grounding the TCC solenoid through the transmission case.