So what is a "Mystery Switch"?
Very simple, it's a switch that allows you to manually control your torque converter lock-up solenoid. It lets you lock your torque converter in any forward gear.
Be cautious with this DIY. If you do not have a transmission that is built to handle some abuse, this modification can be damaging to your tranny. A good torque converter, billet input shaft and valve body, at a minimum, are suggested before using this mod.
The type of switch that you use for this is up to you. If your intent for this mod is towing or using it with an engine brake, I suggest using a toggle type switch. If your interest is racing or dynos, I suggest a push on, momentary type switch to keep you from forgetting it and stalling the truck.
So, on with the DIY......
First, you need to figure out where you want to put the switch. I placed mine so that I could lift a finger from the gear selector and hit the button. I decided to place it on the radio bezel. My switch is a momentary on type switch.
Once you have the location determined, you need to have the materials to do the install. A grand total of about $15 worth of electrical components is all that is needed. The biggest thing you my need to purchase, as most of us do not have these on hand is a pack of 33 ohm resistors. These resistors are necessary for this install, otherwise manually activating the TC lock-up solenoid will set a code and put the truck into limp mode.
Now we can figure out how we are going to rig this up. It's actually very simple, the most time consuming part is getting your wiring neat and out of the way.
This is basically a two wire hook up. One from the torque converter lock-up solenoid wire and one to ground.
What this system does is GROUNDS the TC solenoid circuit.
Here is my basic diagram of how the system is rigged.
The wire we need to tap is the #7 pin on the transmission solenoid assembly. The wire is Yellow w/ a Light Blue stripe.
The connector that you need to remove is located on the drivers side of the transmission and is located directly above the dog ear for the transmission jack.
Once you have pulled out the connector and located the #7 wire (Yellow w/ Light Blue stripe), you need to tap into that wire. The method you use is up to you, I used a t-tap.
Once you tap the wire, you need to run your lead up into the cab. It is easier to feed the wire from the engine bay DOWN to the transmission. I HIGHLY recommend that all connections for this DIY are soldered and shrink wrapped.
Once the wire tap has been completed, you need to weatherproof it. I used a piece of 1/2" heat shrink tubing to go around cover the t-tap. I then went over that with electrical tape.
Once the lead is inside the cab, you can connect your 33 ohm resistor. This resistor is necessary, otherwise this will set a code and put the truck into limp mode. These resistors are approx $0.99 at Radio Shack. Solder your resistor to the wire and then connect the wire to your switch wiring.
Once the switch location has been determined and the switch is mounted, you need to conenct your wires to it. One wire is from the transmission and one goes to ground. Any clean, metal ground will work fine.
Once you have the wires connected to the switch, you are ready to put everything back together and try it out.
It's that easy.
Remember, keeping the TC locked at low speeds will bog the truck and stall it if you come to a stop. REMEMBER TO UNLOCK THE TC.
If you have a set of electronic gauges that shows the TC condition, you WILL NOT see the TC locked when you manually engage it. This is because the monitor gets it's signal from the TIPCM, not the TC itself.
Topic: Mystery Switch Install - 3rd Gen 5.9 CTD (Read 21201 times)