T Converter lockup switch tow haul mode
I just installed a lockup switch on my dash for to manual lock the torque converter.I got this idea from a buddy with a dodge cummins who had a lockup switch on his dash. After searching the internet, there is plenty of info on how to do it, I just wanted to put it here for us to use.
I have had pcm4less reflash my pcm twice and it was way better, but it still would unlock the TC under high load conditions which is exactly opposite of what I want. Un-locking does help a 4 speed auto by making a bit more torque to the wheels and providing a fake in-between gear ratio so it acts like a gear between 3rd and 4th. If the transmission controls were smarter, I wouldn't have cared so much but even after the reflash, mine would unlock when towing into a head wind and stay unlocked for many miles which gets horrible gas mileage and makes a lot more transmission heat. I believe this is the main reason why these have such a bad rep for poor fuel economy.
So here is how to do it on a 2004 I6. (other years may be different)
you need a toggle switch mounted somewhere on the dash and about 4 feet of wire (two conductors). You can poke a hole through the rubber boot under the dash where the big bundle of wires passes through the firewall, just be careful not to nick any of the factory wires.
Next take the cap off the center connector on the PCM module. On the I6, the PCM is mounted right on the drivers side of the intake manifold. If you need more room to work you can disconnect the plug from the PCM. Disconnecting the battery is a good idea, (but I skipped that part).
From here there are one or two wires that will be cut and grounded through your switch depending on how you want the lockup to work. You can connect the ground side of the switch to the fat black wire in the center pin of the plug, I just cut off a bit of insulation and soldered it on.
The main lockup wire is a tan/blk wire on pin 37 (there are numbers on the back of the plug). This will be cut and connect the side going to the trans to the other wire from your switch. The remaining piece of wire from the PCM will need to go through a 100 ohm 5 watt resistor to a 12v source. I just connected it to the backup light fuse in the fuse box. This is only necessary to keep it from turning on the check engine light.
At this point the converter will lock whenever the switch is on IF the PWM solenoid is allowing it to. The PWM solenoid is controlled by another wire that lets the computer make a "softer" engagement of the converter clutch. I tried it this way and it would still be totally disengaged below 1500 RPM and the Partially slipping the TC at 1800-2000RPM.
There is a PWM solenoid valve mod which can be installed in the transmission which will make the PWM on all the time and the converter will be on or off with no slip. This is part of the Transgo shift kit.
I don't have my Transgo shift kit installed yet so I decided to switch the PWM circuit to full on as well. The PWM wire is a brown wire in pin22. I just cut it and connected the trans side to the same switch as the tc wire. Then I use another 100 ohm 5 watt resister to connect the PCM side to the 12v source on the fuse box to keep it from turning on the check engine light.
Now my converter is full locked anytime - anywhere when the switch is on. It will stall the motor if you forget to turn it of when you stop. (thats how my buddys cummins is too).
Here are some negative side effects to be discussed:
When the switch is off the TC is always un-locked. If you used a double pole switch you could probably wire it another way so the off position re-connects the PCM to control the lockup. I like it this way better but I am a control freak.....
The engine may PUSH the vehicle slightly in an emergency stop menuver that could ad a few feet to you stoping distance if you dont flip the switch off in time. This could be fixed by putting a relay in the circuit that triggers from the brake light.
There are some people saying the PWM mod is hard on the torque converter because it allows full pressure on it all the time. I am no expert but from my research, the older 4l60e and 700r4 trannys came that way from the factory so I can't see it being a big deal.
I don't have a lot of miles on it yet an I am going to install the transgo shift kit soon. But I wanted to try it on a stock tranny first. My trans has 100,000 miles on it so I will post back any pros and cons I find.