Non-computer controlled automatic transmissions, specifically GM 200-4R and 700-R4 models, use electric solenoids to activate the lock-up feature on the torque convertor. At the appropriate time, as determined by the TV cable system, an electric signal is passed through a relay to the solenoid that engages the lock-up clutch. When this happens, the internal clutches on the convertor push forward to the internal flywheel, eliminating the built-in slip of the convertor. This can feel like small shift and you will see the engine speed drop 200-500 RPMs.
The lock-up feature is factory installed on vehicles with this transmission from the factory, but these popular automatics are regularly swapped into non-overdrive cars. In order to regain the lock-up feature, you need to wire it. There are ways of making your own kit, but if you use a torque convertor lockup kit like the Painless Performance system shown here, the process is greatly simplified and well worth it. Our local NAPA was more than happy to order the kit and it was in our hands in just a few days. One of the added benefits of the wiring kit is that it also gives you control of when the convertor locks up. You can add a switch to lock or unlock the convertor whenever you choose. If you are drag racing or towing, you want to leave the lock-up off, and other times when you may want to force it on. Regardless, if you want the choice, then you need one of these kits.
For documentation purposes, we installed the kit on a 200-4R transmission that was not installed in the vehicle. This torque convertor lockup kit is easily installed in the car as well, so don’t think you need to pull the trans, you can leave it in place and wire up the convertor.
The process starts with removing the pan. If you have a drain plug, drain it first. Most stock pans do not have drain plugs, so you will need to be careful. We suggest breaking all the bolts loose, removing most of them and leaving a few in the front of the pan. Break the seal of the gasket, and allow the fluid to drain. This way you won’t get soaked. The fluid will take a good 10 minutes to drain. Remove the pan.
With the pan off, you will see the filter, behind that is the valve body. The filter is held in place with an O-ring, pull on the filter with a twisting motion and it should pop out. Now is a great time to replace the filter.
You will see some wires running to a round flat pressure switch, this will be replaced by the switch included in the kit. Using a wrench, remove the switch and install the new one.
At the front passenger-side of the case, there is a solenoid retained by two bolts. Remove these bolts and replace them with the supplied studs.
Install the new solenoid supplied in the torque convertor lockup kit. The solenoid is retained by new nuts that thread onto the newly installed studs. The solenoid is longer than the original, which is why it needs the studs.
On the interior of the driver side of the case, the factory wiring port is located. Disconnect any plugs connected to the inside of the port.
Route the wires coming off the solenoid through the original wire clips, and attach the terminals to the new pressure switch and to the port on the side of the case.
Place the new gasket onto the case and reinstall the pan. The gaskets tend be a pain to install, get each bolt started and then move around the pan one by one. If the gasket slips inside the pan, use a pick to snag it and drag it back in place. Reinstall the pan and tighten the bolts in a criss-cross pattern.
The torque convertor lockup kit comes with a new brake switch. It is a direct replacement for stock GM brake switches. It has two sets of terminals, one for the brake lights and one for the transmission. The transmission terminal is the rear most set. The red wire connects to a 12v ignition source. The second length of purple wire connects to the other terminal on the new brake switch.
Connect the supplied plug in to the outside port on the transmission. This purple wire will control the operation of the converter. The other side of the purple wire connects to the vacuum module that installs as close to the engine as possible. This needs a vacuum line from the engine.
With the installation complete, you can now enjoy the benefits of your lock-up torque convertor. This installation typically takes 2-3 hours, depending on your skill level. Don’t forget to fill the transmission with new fluid before driving the vehicle.
Check out all the drivetrain products available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on how to install a torque convertor lockup kit, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.
A life-long gearhead, Jefferson Bryant spends more time in the shop than anywhere else. His career began in the car audio industry as a shop manager, eventually working his way into a position at Rockford Fosgate as a product designer. In 2003, he began writing tech articles for magazines, and has been working as an automotive journalist ever since. His work has been featured in Car Craft, Hot Rod, Rod & Custom, Truckin’, Mopar Muscle, and many more. Jefferson has also written 4 books and produced countless videos. Jefferson operates Red Dirt Rodz, his personal garage studio, where all of his magazine articles and tech videos are produced.