How to Wire a Switch to Lock Up the Torque Converter on a 700R Transmissionby Robert Moore
Torque converter lockup on the 700R4 transmission is controlled by the TCC solenoid. When the solenoid is engaged, fluid is applied to the torque converter clutch, creating lockup and a direct link between the engine and transmission. This feature is often controlled by the vehicle's computer when certain conditions are met, however this can be bypassed, and a toggle switch can be used to control torque converter lockup anytime the driver wishes.
Gaining Access to the TCC Solenoid
Drive the vehicle onto car ramps, put it in park, and set the emergency brake. Put on safety glasses and place a large drain pan under the transmission pan.
Loosen the transmission pan bolts four or five turns each, and gently pry down on the edge of the transmission pan, being careful to prevent any bending or warping. Allow as much fluid as possible to drain from the broken seal between the transmission and transmission pan.
Place one hand firmly on the transmission pan and hold it to the transmission case. Remove the transmission pan bolts by hand and slowly lower the pan down into the large drain pan. Remove the filter by pulling down on it. The TCC solenoid is connected to the valve body of the transmission.
Wiring the Solenoid and Sealing the Transmission
Disconnect the negative and positive terminals of the battery. Locate a body ground under the vehicle and attach one end of the 16-gauge wire to the body ground. Run the ground wire through the transmission wiring grommet, and attach it to the negative side of the TCC solenoid.
Decide where the toggle switch will be located within the vehicle, and install it. Connect the 10 amp fuse block (without fuse installed) to the positive battery cable, and route the wire through a firewall grommet, into the vehicle. Attach the constant side of the toggle switch.
Attach 16-gauge wire to the "on" position of the toggle switch. Route this wire through the rubber grommet in the firewall and down to the transmission. Direct the wire through the transmission wire harness grommet and attach it to the positive side of the TCC solenoid.
Install the new filter into the transmission by gently pushing up on it. Place the new transmission pan gasket over the transmission pan, aligning all holes. Press the transmission pan back onto the transmission and hand-tighten the bolts that secure the pan to the transmission. Torque the transmission bolts to the manufacturer's recommended torque with a small torque wrench.
Secure all 16-gauge wire to the vehicle with zip ties to prevent any hanging wire. Ensure the toggle switch is in the "off" position, and install the fuse into the fuse block. Add transmission fluid through the transmission fill tube, checking the fluid level every quart to prevent over filling. Back the vehicle off the car ramps.
- The toggle switch can be installed in any location inside the vehicle.
- Always leave enough extra length when cutting wire, so it can be secured later.
- Never turn on the torque converter lock-up at slow speeds, as this may damage your vehicle.
- Never attempt to drive a vehicle with low transmission fluid.