Torque Converter Lockup Switch for Late Model Automatic Transmission Equipped Mopars
Install of a Torque Converter Lockup Switch for Mopars Short Cuts
by: Stevan Gajic

Introduction

How many times have you followed a manual transmission equipped vehicle down a hill and watched him use only the compression of his engine to hold him back and wished you could do that? Manual transmissions use a clutch which does not slip when fully engaged, transferring all the power from the engine to the wheels, or vice-versa. Automatic transmissions, on the other hand, use a torque converter to multiply the engine's output allowing shifts while under full power, among other things. This slippage, however can also reduce the engine's holdback ability -- so you're more likely to accelerate downhill even with your tranny locked into first gear.

Many manufacturers today use a locking torque converter on automatic transmission equipped vehicles. The reason this is done is to lower the operating temperature of the transmission, since slippage builds up heat, as well as to boost fuel economy. The on-board computer controls a solenoid which locks and unlocks the torque converter at the correct times on the highway. It doesn't, however, know how to use this neat capability in off-highway situations. There's no reason we can't use this great feature ourselves by simply installing a manual switch to toggle between locking the torque converter or letting the computer control it. Please note that because of the increased number of electronic components, this trick doesn't work on 1999-and-up 24-valve Diesel-equipped Ram trucks.

Installation

When installing the circuit bridge make sure there is no possibility of a short to ground.

First note that some vehicles initially will need to be taken to the dealership to have the latest version of the powertrain control software flashed into the computer. Once that's done, the install goes easily enough. You will need 2 tab terminals (male), 2 tab connectors (female), 1 switch (common Radio Shack variety will do nicely), a tap splice, an o-terminal, and some wire. The first step is to use a short piece of wire to connect the 2 male tab terminals, thus making a circuit bridge. Once this is done, locate the transmission control relay in the main fuse box. Pull it and install the circuit bridge into the 2 slots that are parallel. This provides the power to the lockup solenoid and will be electrically hot so make sure it can't short to ground accidentally. You won't need to reuse the relay.

Mount the switch in your dash in an easy to reach, out of the way place. Make a wire with a female tab connector on one end and the o-terminal on the other. Make sure it's long enough to run from your switch to a convenient grounding location. Attach to ground there and connect to one of the non-center terminals on the switch. This is the side that will be the locked position when finished. Locate your Powertrain control module, and on the connectors, locate wire B11. This will be the orange wire with a black stripe on it. Tap into this wire, make sure not to cut it, and run from the wire to your switch, through the firewall. Install a female tab connector on the switch end and attach to center terminal. Reinstall any panels you may have removed in the process of the install and take a test drive.

Do not cut the wire but only splice into it using a tap splice. Then run the wire to ground with an interrupting switch inline.

Effects on Driving

When the torque converter switch is in the off position there should be no change in vehicle operation. While the switch is turned on, however, the transmission will upshift as speed is increased but will not downshift until the converter is unlocked. It will also be possible to stall the engine if you fail to depress the clutch while coming to a stop with a manual transmission.