This has come up from time to time and since my info. on it is buried in my gauge install thread I thought it might be best to post the info here in its own thread.
So the idea behind this is to install a switch that can manually override the unlocking of the torque converter. As y'all likely know, with the E4OD, if you just lift your foot off the throttle the converter unlocks. When you touch the throttle again the revs pick up while the converter locks up and the revs come back down. Don't believe me? Try it.
Of course, this is a nuisance and generates torque converter heat. I don't know about y'all, but I want to keep my E4OD alive for as long as possible! So a buddy of mine told me a trick. Bill at http://www.dfuser.com/
told me that if I tap a wire leading to the tranny and ground it through a switch that I can manually lock the converter. Intrigued, I decided to research it more and went for it.
It's painfully simple for something that might otherwise seem rather daunting.
1. Locate a large wire bundle under the truck next to the transmission. Look for a purple/yellow wire. On my '96 there was only one and I only found it after cleaning off the wires. They were dirty.
2. Tap into that wire and run the wire up to your dash area or wherever you want to install a switch to control the converter. I mounted mine on the dash like such....
3. Mount the wire to the switch and ground the other tab on the switch so that when you flip the switch it will ground that wire. The grounding of the purple/yellow wire is what locks the converter.
Now my buddy, Bill, sells a really cool switch. It's a three position toggle switch. When I flip the toggle down, it locks the converter. So even lifting off the gas or hitting the brake, the converter stays locked. It's great on the highway when you're in traffic, but never going very slowly.
When I flip the toggle up, it also locks the converter, but you have to hold the toggle up or it will return to center/off. It's called a momentary switch. Anyway, Bill sells them and they're cheap! Comes in handy if you're going to go up a big hill or something and want the converter locked for just a brief period of time.
The only thing to watch for is if you forget to unlock the converter and you go slow enough, you may trip your check engine light. I did it once when I forgot and slowed down to 10-15 mph!! WAY too slow. Keep in mind normally my converter won't lock until 27-28 mph. I got Advance Auto to clear it for me and all's well. Sometimes the CEL will just go off after a day or two, but it doesn't harm anything as far as I know. I only had it reset once. The two other times I did it, the light eventually just went off. I've also had the O/D light flash on the stalk a couple times, but it's not too common.
Bill's been doing this trick for his customers for years. It's super handy, informative, and will help me preserve my tranny.
I got a little fancy with my gauge install. I wired a green LED next to my tranny temp gauge. The toggle switch will also provide a ground for the LED and so it illuminates whenever the converter is locked....so I don't forget too often to unlock it as I slow down.
And here's the gauge install thread for those interested.