KC_kid

iTrader: (5)

I don't fully understand when or why the torque converter locks up, please educate me.

I've read it needs to be 75deg & 45mph to engage lockup. Does it matter what gear you're in? What happens when you downshift, does it stay locked up? If the converter is locked and you hit the gas, does it stay locked? If your cruising down the interstate in OD with TC locked and you come up on a hill, tranny downshifts, does TC stay locked?

Is there a way to tell if/when it locks or if/when it unlocks?

Just looking for general info here, please throw out anything useful in addition the questions. Thanks

Gadgetized

iTrader: (9)

Think of the torque converter like 2 box fans touching each other. The first box fan is the only one with the power on. The 2nd one is moved by the air off of the first one. The 2nd fan will never have 100% power transferred to it. If you were able to lock those fans together, it would run at 100%. That is where a lock up comes in. If you can lock the engine through the lock up clutch/clutches, you lower heat, help mileage, and transfer 100% of the power.

The lock up can be set wherever you want it in the tune. If you have a stock or single disk clutch, I woul not suggest to have it lockup unless you are cruising at highway speeds. When it is engaged it feels like it is shifting into another gear. Drive at highway speeds, and pull it into drive. Then shift it into OD. It will shift into OD, then the next time it feels like a shift, that is the lockup. When the tranny is shifting the lock up is not applied as it would ruin the clutch very soon.

If you have a multi disk lock up clutch, you can apply it while going WOT as there is more surface area of clutch material.

Slammed96

iTrader: (5)

Gadgetized has a good explanation, to build on it, the best way to "see" your converter lock on the highway, is to cruise at a steady speed in OD, slowly give the truck gas, after a certain point you will see/feel your RPM jump slightly, in my truck about 300 or so, that jump is the converter unlocking under acceleration. You will also see this in cruise going up a gentle hill before your truck downshifts.

Circle-D

iTrader: (21)

Good info Gadgetized, and to expand a little further... The lock up clutch inside the converter is controlled/activated by fluid pressure. Fluid is sent down the center of the input shaft in the off position. Then the lock up solenoid is energized and fluid is redirected around the stator and pressurize the converter applying the clutch. Like mentioned above, you can turn on the lock up when ever you want, its all in the tune....

Chris

KC_kid

iTrader: (5)

Thanks for the explanation. I understand the concept of a torque converter, what it is and why it's there. I have a stock 6l80e and TC and I have a Blackbear Autocal tune. I also understand that you can tell a small RPM difference when the converter locks/unlocks, but is there any other way to see it? For example, if I do a log with the Autocal, can I view when it locks/unlocks? Or with a scan tool type program? I'm using the Android torque app with the bluetooth OBDII adapter.

Also, I think it was answered but I was curious, if my truck downshifts on the interstate, the torque converter will unlock, correct? I'm asking this because I downshift all the time while trying to maintain speed and I'm wondering if I should choose a slightly shorter gear to minimize this, or go with one that puts me in a lower cruising RPM range. I want this discussion to be about torque converter lock/unlock and not about gear selection, but that is part of the reason why I'm asking. I want to maximize MPG on the highway and I feel like attempting to keep the TC locked will help with that effort.

Gadgetized

iTrader: (9)

Yes, you can tell with the Torque app. How well do you know the software? You will need to more than likely set some stuff up in the app to make it work, but it won't be too hard. You can't command it to lock up though. You can only tell when it is locked up.

KC_kid

iTrader: (5)

Not that well, yet. I've only had it for about a week and haven't had the chance to play around with it yet. I need a dock or something so I can easily see the screen while driving.

Do you mean that I can tell by monitoring the RPM in the app? Or it actually tells me I'm locked up. I'll see what I can figure out with it...

Circle-D

iTrader: (21)

I have never used the app, but I would imagine there is a parameter for TCC apply or slip you could watch.

Chris

silver-mod-o

iTrader: (15)

Good discussion happening here

You'd probably be surprised how many people who race these things have no idea how a converter works and the difference in locked/unlocked. Knowledge is a great thing, and good on you for not being afraid to ask a simple question.

Slammed96

iTrader: (5)

Im going to guess along with Chris and say it will probably tell you when your TCC lockup solenoid is engaged or disengaged. Thats the best way I could think they would be able to remotely monitor the converter's activities.