Torque Converter Clutch Disable On Demand

[1997ThunderbirdLXV6]

Has anyone ever added a switch to manually control (inhibit) torque converter lockup at will?

Think stock tune. I imagine it would be a matter of fooling the PCM into thinking the brakes are applied when they're not.

Yes, I'm going somewhere with this question. I've done plenty of monitoring of TCC slip recently using my OBD Fusion app. In 3rd, there is A LOT of what Ford calls "controlled slip", which is an attempt to be most fuel efficient while also softening the effects of releasing and reapplying the throttle in urban traffic, etc.

It causes wear on the torque converter, but more so it can be annoying in hilly terrain. My neighborhood is mostly hilly with 25 mph speed limits. You drive around in 3rd, and the transmission lugs the engine at 1,200 rpm or so with TCC locked vs. a healthier 1,500 rpm with TCC unlocked. Yes, I guess I could simply put it into manual 2nd... Humor my question though.

 

[Grog6]

Yes, you can do that; if you use a double pole switch, you can switch between eec/manual.
Grounding the tc solenoid will enacle tc. I DO NOT ADVISE IT.
With the box I made, you can switch gears as you wish.
There are several ways to ruin a trans using that box. tc should be ok, possibly.

the eec may detect it, if it does, the od light flashes, and you go to limp mode; only 2nd gear, and no advance.
Cycling power usually clears that, but I've had to clear the eec.

 

[MadMikeyL]

If you only interrupt the brake on/off switch signal to the ECM, I don’t think it would throw any codes or cause any limp mode. But you would have to interrupt it only going to the ECM, otherwise your brake lights would be on all the time. Interrupting the TCC signal wire from the ECM to the trans definitely would cause codes, and likely limp mode.

 

[1997ThunderbirdLXV6]

If you only interrupt the brake on/off switch signal to the ECM, I don’t think it would throw any codes or cause any limp mode. But you would have to interrupt it only going to the ECM, otherwise your brake lights would be on all the time.

Yes, understood about the brake lights.

But does the PCM do anything  else with that information? I mean, I would be simultaneously on the throttle and on the brakes (not actually on the brakes, but the PCM would think I am). Would the PCM change any behavior other than TCC not locking up?

Interrupting the TCC signal wire from the ECM to the trans definitely would cause codes, and likely limp mode.

Understood, and I was not suggesting that at all.

Yes, you can do that; if you use a double pole switch, you can switch between eec/manual.
Grounding the tc solenoid will enacle tc. I DO NOT ADVISE IT.
With the box I made, you can switch gears as you wish.

Yeah, I was not suggesting that level of manual input.

I was only suggesting the ability to switch between A. automatic TCC lockup per PCM (=stock), and B. no TCC lockup at all.

 

[Grog6]

Dinking with the trans controls is a great way to ruin a trans. I was diagnosing an already broken trans, and had nothing to lose. I had a leaking vb, that included the direct clutch and TC. I literally put a mushroom stamp on a VB.


This is what happens if the 2-3 accumulator freaks due to the 127.5 mph upshift bug.
I had OD off, when I hit the bug. It shifted about a thousand times between 3 and 4 before I lost pressure. This VB was toast.
This was mostly my fault, I forgot about the bug until Don told me what the deal was.

 

[1997ThunderbirdLXV6]

Dinking with the trans controls is a great way to ruin a trans.

Ok, but...

Are you saying that in response to my suggestion?! Because I felt what I suggested seemed perfectly safe (?). I mean, what harm can an unlocked torque converter do? At most, create heat; but since I installed the external cooler, I no longer worry about heat too much.

 

[1997ThunderbirdLXV6]

...and I'm at no risk of reaching 127.5 mph.

 

[1997ThunderbirdLXV6]

Other question while I'm reading up about this:

What's the difference between VSS (vehicle speed sensor) and OSS (output shaft speed sensor)?

I thought the VSS was on the...output shaft (?).

 

[MadMikeyL]

In our cars, we only have the VSS, which is the gear driven one. Later cars use the OSS, which is the magnetic pickup. And some later 4r70s use both. But for your purposes, the ECM interprets OSS based on VSS signal. As for other things the ECM depends on brake input for, I don’t know off the top of my head, but I doubt it would be anything that would affect drivability. A quick test would be to put your left foot just barely on the brake enough to turn the lights on and drive it and see what happens.

 

[1997ThunderbirdLXV6]

In the 1997 Ford EVTM, it shows both sensors. But these manuals aren't always error free...

 

[1997ThunderbirdLXV6]

Here's an interesting tidbit I came across in my reading.







So there's a limitation to my entire idea in that above 1/3 throttle position, it'll still do whatever it wants to.

 

[Grog6]

That's to enable two-footed driving; ask a cop. It's used in pursuit.
I went to driving school with the state troopers in nashville in '79.
Basically, you maintain half to full throttle while brakeing, keeping the engine in the powerband.
It kills trans', and eats brakes. But its faster in traffic.

 

[1997ThunderbirdLXV6]

Thanks, @XR7-4.6 for moving the posts.

I'm undecided on this project, mostly because, as @3_97_Sports pointed out, I could achieve the same result by simply tapping the brake. But A. I'm not in the habit of getting my left foot involved, and B. that's just a very brief unlock.

Too cold today to do anything outdoors, but at least I can theorize.

Here is the basic diagram:




The red box is RELAY 1 in the drawings below.

Now, to understand the drawings below, remember that I have a small 4-way stalk on the right of my steering column (a repurposed Mercedes cruise switch); currently its only function is for O/D off.



This 4-way switch consists of three normally open and one normally closed switch.

Option 1

For the purpose of this drawing, the box marked "STALK" utilizes one normally open and the normally closed switch.

RELAY 2 is wired to be a latching relay. That means that, if I disable the TCC using this setup, it won't lock up until I reactivate it.



If I went with this, I think I'd want to have a light akin to the O/D OFF light to illuminate when the TCC is disabled.

Option 2

Another option would be to only unlock the TCC while I hold the switch. Much simpler...but somewhat tedious while steering.




Option 3

I haven't drawn this out yet, but Option 3 would be a self-canceling TCC disable. I would still wire up a latching relay activated by the steering column stalk, but it would unlatch the next time I hit the brakes.