Manually lock your Torque Converter (TC)

Old 04-11-2009, 10:36 AM
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Join Date: Sep 2008
Location: N.J. Shore Area
Posts: 3,045
Year: 1994
Model: Cherokee
Engine: l6 HO
Default Manually lock your Torque Converter (TC)

I originally made this up for locking my TC on the beach but found it works on DD pretty good too. After hitting the lock button at a certain speed and RPM it will lock the TC up, it WILL NOT engage in my jeep while sitting still but it will lock after you get moving which means it wont lock if you are just sitting so it must have a safety built into it so you cant lock the converter unless you moving at a certain RPM in a certain gear.
I wrote this write up in case anyone wanted to try it for themselves...TrekkerJmm (Tj)

Here is a pic of the relay setup. I used 2 factory jeep relays to do this because I had extras laying around. What the relays do are to send a 12 volt signal to the TC to manual lock it when you want and after hitting the brake it will dis-engage.

I used small wire to connect the relays together and very small speaker wire (Radio Shack Catalog #: 278-1301) 24 gauge wire to run to the Momentary button, Ground, brake pedal switch and to the CPU. I bought a roll because I plan on doing a transmission 1-2 gear manual lock next.

Connect #30 on both relays together along with #85 on the first relay.

This will go to the blue wire from the brake/cruise control switch on the brake pedal (yours may be a different color but this wire has +12 volts when the key is on until you hit the brake pedal then it loses the voltage and voltage will return when you let the brake up again) This wire will dis-engage the TC lock after you hit the brake pedal.

Connect Both #87ís on both relays together and #85 on the second relay together,

This will be the +12 volts that will go to the White wire with the black stripe (c14) on the CPU under the glove compartment.

Connect #86 on the second relay to a ground.

Connect #86 on relay 1 to #86 on relay 2 with a momentary push button in between them (this will be the signal to lock the converter)

This is what my relay looks like.

I used heat shrink and tape to cover the relay so it wouldn't short out the put it under the shifter handle out of the way of all moving parts.

This is the shifter handle I used that I got from Pep Boys ($23), I drilled a hole in the top and put a micro button (Catalog #: 275-1547, $3.49) in there from Radio Shack. You can use any momentary button or switch and mount it anywhere you like.

I had to add a spacer in the new shifter handle and also had to drill the bottom coupler to make it fit on the factory shifter mount. I used a 30.06 bullet shell but you can use anything that is hollow so you can run the wire through it.

This Plastic piece is inside the shifter. I had to use a Dremel to make notches in the top and bottom of the piece (I blacked out the parts that needed to be notched) so the small speaker wire I used would not bind up when pushing the top of the shifter.

This is the wire I cut from the CPU under the passenger side dash under the glove box. The color is white with a black stripe and the number on the plug is C14.

You MUST put a 3 amp diode in line from the wire from the relay (numbers 87, 87 and 85 the purple wire in the first pic) and the white wire with black stripe (C14) so no voltage feeds back into the CPU. Take the wire that you cut coming from the wire harness and the purple wire from #87 87 & 85 and solder them together with the white band of the diode facing the two wires. After your done with that step solder the wire (white w/ black stripe)from the plug end of C14 to the other end of the diode, then using some heat shrink or Black tape seal it up. I got the Diode at Radio Shack and the catalog number is 276-1143 and cost $1.59 for two but you only need one.

Here is what it should look like when your done.

I have been using it for a few days and it works fantastic!! You will notice that when you engage the TC lock your RPM's will drop down around 500 RPM's and when you give it gas the trans will not slip (Acting like a manual trans) and whenever you tap the brake it will dis-engage. Have fun...Tj
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