The above pictures show the installation of my TC lock-up mod.
Clicking on each picture will open a larger version and will eventually
have more detailed text under them.

When the switch is in the left position, the green light will illuminate only when
the TC has locked up as commanded by the computer.

When the switch is in the right position, the red light will illuminate to indicate
that I have manually locked the TC regardless of what the computer thinks. The green
light will continue to monitor the computer's command to lock the TC. As such, it is
possible to have BOTH lights lit when in the right position.

I used pre-wired Radio shack 12v LED's and a "triple pole, double throw" switch is needed
to do this mod as I have done it. I couldnt get a 3PDT switch and had to settle for a 4PDT
that I found in the engineering parts bin at the radio stations I work at. Unknown part
number or manufacturer. Probably goes to a broadcast console mixer. *shrug*

I cut and tapped the TC lock wire (purple with yellow tracer on my 2000 PSD) by
tracking the correct wire from the plug located on the drivers side fender well down to
a reasonable work location near the floorboards on the drivers side. I split the loom open
to see which wire i was wiggling at the top and then cut it. The reason I had to track the wire
is there are THREE purple with yellow tracers in my wire harness, and they all three
go to the tranny, but to different functions.

There are 4 connectors underneath the brake master cylinder. 3 black ones and one grey one
You want PIN-6 of the forward most GREY connector. Pinout is as follows:

(4) (3) (2) (1)
(8) (7) (6) (5)
(12)(11)(10)(9)
(16)(15)(14)(13)

I ran a 4-conductor wire from my dash 4x4 switch, under the steering column, and then
followed the shift cable to the floorboards and made a small hole for the wire to go
under the truck. I then connected one wire (green in my case) to the transmission side
of the TC lockup wire that I cut earlier, and another wire (white) to the PCM side of the
same cut wire. Soldered and shrinkwrapped. Zip Tie and tape up and your done under the truck

Back in the cab, I used a third wire from my 4-conductor cable (black) to wire a ground
to the dash subframe, and finally the last wire (red) I tied into the "Customer Access"
switched hot wire found just above the OBD-II port under the right side of the dash.

I had to trim away some of the misc plastic on the back of the 4x4 panel, but there was
just enough room to make the switch fit. The last picture is my futile attempts to make
this mod work with a double pole, double throw (DPDT) switch before I realized I needed
a third pole in my wiring. (Circled with AHA!)

BREAKING NEWS!!!

Keep in mind, you will still need to cut the TC lock wire and bring it into the cab in order
for the lights to act independently of each other, but NOW you can use any DPDT switch of your
choosing instead of the 3PDT switch I had to use in my earlier design.

Disclaimer!!!

OK, I think I need to add some disclaimers to my webpage...

First off, you DO NOT want to "lug" your automatic transmission by "locking it in first gear at
an idle". The line pressures on the lockup plates are NOT HIGH ENOUGH at idle to hold the lockup
clutch and you will burn up your torque convertor over time. The primary purpose of the TC lock
mod is for TOWING. The TC lock mod, combined with an exhaust brake will allow you to travel down
long grades with minimal use of your service brake. This equates to cooler brakes at the bottom,
and longer brake life.

The TC lock mod is also good for long uphill driving at speeds BELOW lockup speed (about 45mph).
Keeping the Rpms up by using 1st or 2nd gear and locking the TC will allow you to keep tranny temps
down during long uphill (and uphill towing) situations. You should unlock your TC at speeds below
about 25mph or RPMs below 1000 so as to avoid TC damage from low line pressures.

This mod works on all years of 7.3l powerstrokes with an auto tranny. It does not work on 6.0/torqueshift
trucks. Wire colors have been known to change tho. The absolute positive identification is pin 4 of
the tranny plug. Located on the *passenger* side of the tranny, and plugs *DOWN* as if into the pan. The
exhaust pipe usually blocks good access to that plug.

Yes, you can do this mod without LED's by just GROUNDING the TC lock wire using a switch and a skotch-Lok.
You can also add an LED without cutting the TC wire. The only reason to cut the TC wire is to monitor both
the PCM and the TC Override seperately, such as above.