700R4 / 2004R Torque Converter Lockup Control Kit

The GM 700R4 and its overdrive cousin the 200-4R both use an electric torque converter clutch (TCC) solenoid that needs a switched 12-volt signal to lock the converter in top gear. When you drop one of these overdrive automatics behind an older engine that never ran transmission wiring, nothing tells the converter to lock up, so it slips and runs hot on the highway and you lose the fuel economy the overdrive box was swapped in for. This kit supplies and controls that lockup signal.

It uses a hydraulic pressure switch that threads into the transmission's fourth-gear pressure port, so the converter clutch only engages once the trans is actually shifted into overdrive and building line pressure, not in the lower gears where lockup would lug the engine. The kit includes the pressure switch, an in-line fuse, and the wiring to feed the TCC solenoid through the case connector.

Note the fitment requirement: your transmission case must have a 3/8 NPT threaded fourth-gear pressure port for the switch to thread into. Most 700R4 and 200-4R cases have this port; confirm yours before installing. This is a control and wiring kit only, not a torque converter or solenoid.