I know I've seen a write- up on this, but I've searched around and can't find it.
I want to have a switch to keep the tc unlocked. It helps me when climbing with a heavy load. I can in essence split gears...

TIA

Phy

 

You have one already,that is,if you don't mind the flashers blinking.Simply turning on the flashers will unlock the converter.Keep in mind,when the converter is unlocked,trans temps run much warmer (like the old C6 trans) so watch your gauge.

 

Thanks for the reply, HDXLT.
I use the flashers now, but would rather have a switch. I do watch my trans temp compulsively, and understand that with the converter unlocked the beating the fluid takes inside the converter will raise temps more quickly. (One of these days I need to build that trans fluid thermostat valve setup you wrote up, to route fluid to the external cooler rather than the radiator when it's warm.
The reason that the flashers unlock the converter is because the PCM unlocks the converter when you hit the brakes, correct? The PCM watches the brake light circuit to do this, and the flashers also energize the brake lights, correct? If so, I could find the wire where the PCM taps into the brake circuit, connect 12v from a dash switch there, and use a diode to keep it from back-feeding the brake light circuit. This should make the PCM think the brakes are on, and unlock the converter. It's kinda taking the long way 'round to get there, but it should work.

I did find online last night a write-up of a comprehensive circuit to control lockup. It's more complex, but looks really good. It has positions for unlock, auto, and lock, with LED's and such. One good feature is that even in the lock position, it allows it to unlock in 1st and 2nd gears. This ensures you don't forget and try to stop with the converter locked.
If I get ambitious, I may try to build this circuit...

 

That's a certain way to overheat the transmission. The radiator cooler removes more heat from the ATF than the external cooler. Why in the world would you want to remove the best cooler you've got when the trans needs it the most?

 

Yeah I wouldn't ever bypass the radiator.I have t-stat in front of my rad and aux cooler to help get temps up to 180F.I have no problems maintaining around 180-190F temps at the test port.

 

does all the e40ds do that witht the flashers?

 

Thanks Mark, I didn't know that about the radiator cooler. I thought when the coolant gets hotter, that it would be detrimental.

Thanks for clarifying, HDXLT.

Right now, I have the radiator cooler and an external cooler hooked up in series. I'll just leave it like that for now.

Phy

 

Yes, getting the ATF hotter would be detrimental. But I noticed you called it a cooler. A cooler does not heat things, it cools them. The radiator cooler always cools the ATF. I've measured this in ambient temperatures from -40 t +115°F and I could never find a condition where the coolant in the cold side of the radiator (where the trans cooler is located) is hotter than the ATF. It's a myth that the ATF flows through the radiator to warm the ATF. That's NOT true.

 

Thanks, that makes sense. I hadn't thought about that before. Even when the engine coolant temp is high, that's at the top of the engine, where the coolant is leaving the engine and going to the top of the radiator. By the time it's at the bottom of the radiator, it has cooled down considerably, and that is where the ATF cooler is.

Thanks, Mark!