Does anyone know which wire to put the switch in to keep the torque converter unlocked on my 98 4l80e. I have heard of guys putting a 3 way switch in to use pcm , always locked snd always unlocked?
Why would you want the TC unlocked all the time? That sounds like a recipe for a quick trans melt down from the heat generated.
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As b salgado says, an unlocked torque converter creates a lot of heat. Although newer truck transmissions are designed to handle this heat without frying, higher heat does mean accelerated wear.
We have an automatic transmission business in the family, and I personally do everything I can to avoid towing with my torque converter unlocked. I manually downshift a gear if the load (steep hill, headwind, etc.) causes the torque converter to run unlocked in the higher gear. I have towed with GM OverDrive automatics since buying our first ('84) Suburban, put over 100K miles on every one before trading, and with the above rule in mind, as well as regular fluid and filter changes, I've have never had to have a trans repair or replacement.
I'm at a loss as to why you would want to do this, unless your torque converter clutch is failing. If it is, and you tow with the clutch unlocked, trans failure won' be far behind.
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I believe the purpose of the modification is to be able to keep the torque converter locked in all gears for towing and engine braking and to avoid it switching from locked to unlocked constantly on rolling hills. I don't know anyone that would want to purposely leave it unlocked. The nature of the switch in the system would allow a position for fully locked as well as fully unlocked even though unlocked is not desired. Simple to defeat, just don't throw the switch in that position.
The reason for wanting to keep it unlocked is in stock form the converter locks up and i loose 400 rpm this kills my acceleration.only wanting to keep it ulocked to merge on freeway. engine braking is already good stock. I had the same truck without lock up and it was fine.
So, can't you just crack throttle a little further open to get acceleration and unlocked TQ? This may include a gear drop I know. Correct me if I am wrong, but lugging in a high gear has no advantage over letting the trans pick it's optimum gear and converter combination. That's the trouble with automatics, they have a set of parameters, we don't get to decide!
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black flag racing wrote: The reason for wanting to keep it unlocked is in stock form the converter locks up and i loose 400 rpm this kills my acceleration.only wanting to keep it unlocked to merge on freeway. engine braking is already good stock. I had the same truck without lock up and it was fine.
It sounds like you got a problem with your truck. I can get my TC to lock and unlock just by adjusting my right foot. Hills are not an issue. It took me a while to "learn" how to drive the truck. If you pay attention to your tach, it is pretty easy when you figure out where it locks and unlocks. You are correct about the 400 RPM difference, now you just have to learn how to make it do what you need it to with your foot. It is actually easy and no modifications are necessary.
Can we assume you are already running out of OD and wanting more oomph? Yep then unlocking that converter will give you more and a lot of heat. I think that is a question that has to be answered up front.
Some folks may be comaparing your unit to newer ones. My truck (different brand) will go to torque converter lock up when out of overdrive. That serves me well for what you want.
You cannot unlock my converter by mashing on the foot feed, all that will result is a huge roar when the thing kicks down a gear and the torque converter unlocks momentarily for the shift, then the R's go nutso, I don't do that.
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