TCC 3rd gear lower/upper limit vs. TPS%

One of my previous issues, which I thought was an actual transmission issue, may not be, although I still think the transmission in my truck could be due for a rebuild in the future.

Let me preface this by stating that I was considering going back to a 1228062 ecm, but due to the lack of defined parameters available in the xdf for that ecm, I am going to stick with the 1227747 ecm.

In any case, back to the reason for this thread.

I need to get the TCC locking up properly and so far, I've since figured out that with light acceleration, the TCC was locking up too soon, which I think contributed to making me think that there was a tranny issue when I mentioned it a couple of weeks ago.

I've changed that parameter for the 3rd gear lockup and it seems to be shifting smoother without the knocks from hell from locking up way too early.

Now the issue is acceleration that is more than light.

Seems that the tcc doesn't want to lock up until 4th.

Not liking that because it seems the rpm's climb too high in 3rd until it shifts into 4th.

That brings up the TCC 3rd Gear Upper Limit vs. TPS% parameter.

Attached is a data log and bin for example and is a current bin.

I am guessing right now, but based on the data run, I am thinking that upping each cell another 2% might get the shifting closer?

Thanks!

Do you understand how the lower and upper limits work? The TCC will lock when the %TPS is below the lower limit and it will unlock when the %TPS is above the upper limit. It won't change state with the %TPS between the limits.

I've seen it listed as the TCC locking when between the limits which is wrong.

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Originally Posted by lionelhutz

Do you understand how the lower and upper limits work? The TCC will lock when the %TPS is below the lower limit and it will unlock when the %TPS is above the upper limit. It won't change state with the %TPS between the limits.

I've seen it listed as the TCC locking when between the limits which is wrong.

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Oh man.....I swear I read the description for those parameters and I must have been asleep or something......

Just so that I am clear, with the current settings, the TCC will not lock when I accelerate at I'd consider a moderate rate.

If I want the the TCC to lock with more than "grandma acceleration", I'd want to up the "lower limit" and drop the "upper limit"?

that's good.

the tcc locking during any type of acceleration is incorrect behavior for that component.

any settings that allow it to lock during acceleration are to avoid unintended momentary disengagement of the tcc under rediculously light acceleration.

the tcc should only be used in 3rd and 4th gear crusing in an operating range near or below the stall point of the torque converter, where torque converter would be too slippery, cost you fuel economy, and generate too much heat over a long cruise.

if it's revving too high between shifts, that's a shift point thing. the lockup clutch shouldnt be tuned in to try and work around that fact. it isn't designed to hold up under torque or anything.

I was under the impression that the TCC locking up during normal acceleration was normal.

Thanks for explaining that, it's appreciated!

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Originally Posted by damanx

I was under the impression that the TCC locking up during normal acceleration was normal.

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It is! Under the conditions you set forth in the bin. You would not want TCC on as soon as in 3rd or 4th but as you reach your speed it should lock and stay locked within the TPS guidlines.

You would not want it on during high load like WOT... although some newer models do.

i hate the way the older style TCC stuff was setup..... TCC load limits indexed against MPH makes the space pope cry. later masks that indexed against TPS% are so much easier to work with.

anyways, FWIW, i run with the converter locked up to about 90kPa(and at that point, a downshift isn't out of the question).... i'm not a fan of the TCC unlocking for anything other than a downshift(either by coastdown or foot to floor throttle). i want to say some/a lot of calibrations actually lock the TCC when above a specified RPM too, though it is quite high, i want to say near 5000RPM for most applications i've looked at.

$42 has four qualifiers, CTS, MPH, RPM and then the TPS % High and low. Seperate for 3rd and 4th gear. So it's pretty easy to get it right where you want.

There's also a mandatory TCC lock MPH Parameter.

Low gears means third. High gear is 4th or OD.

Quote:

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TCC Load Upper Limit Vs MPH, (Low Gears)
TCC Load Lower Limit Vs. MPH, (Low Gears)
These two tables contain the upper and lower load limits (%TPS) between which the TCC can be locked when in low gears. The TCC will unlock if the load is above the upper limit or below the lower limit.

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I remember seeing the 5000 rpm limit that you are talking about Robert.

Tomorrow I'll get a log and see if I can explain better what I am asking about.

At best right now, and kind of guessing at the numbers, but it seems that the TCC doesn't lock up in 3rd even when accelerating at a rate where the kPa might get to about 50, maybe 60.

Quote:

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Originally Posted by damanx

At best right now, and kind of guessing at the numbers, but it seems that the TCC doesn't lock up in 3rd even when accelerating at a rate where the kPa might get to about 50, maybe 60.

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I find that acceptable MAP to be locked, not to high a load. But if the High and Low TPS% aren't set right? It won't! There's no MAP in the qualifiers for TCC lock.

Do a data log on a open road and steady TPS, see what it does. Next log hold the go peddle a little further, higher TPS% etc... and post it up. You'll figure out which needs adjustment.

Like ADSU looks like 49.92% TPS is the max for TCC to stay locked in either gear. Which would work fine in my V8 with 3:73 gears but maybe not so good with a V6 and ? gears?

Yes, v6 with 3.73 rear.

I suppose that there is the possibility of a tranny issue too.

Well yeah...

If you go by a tranny shop that has cutaways you'll see the older TCC has very little clutch surface, this is the reason for it to be unlocked during high load... or it will slip and create lots of heat!

Newer TCC like 95 up had PWM TCC and the clutch was bigger and much better grade material.

Quote:

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Originally Posted by damanx

Oh man.....I swear I read the description for those parameters and I must have been asleep or something......

Just so that I am clear, with the current settings, the TCC will not lock when I accelerate at I'd consider a moderate rate.

If I want the the TCC to lock with more than "grandma acceleration", I'd want to up the "lower limit" and drop the "upper limit"?

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EagleMark posted what Tunercat says, but the description is wrong.

What steveo posted is correct. You really don't want the TCC locking unless you're at light acceleration or basically leveling out at speed. You need to work on the governor if you disable the TCC and the transmission isn't shifting when you want it it.

To get it to lock, the lower limit has to be above the %TPS at the speed you are traveling.

The %TPS upper limit has to be higher then the %TPS lower limit.

I tend to first set the TCC so it will just be locked. I go for a drive and record the %TPS at the different speeds I would drive in 3rd and 4th gear. I then set the TCC so it unlocks at about 20% more %TPS at each speed, which would be the upper limit table. Set the %TPS lower limit about 8% lower. For my driving, I want to accelerate if I've added 20% more throttle, so unlock the TCC and go.

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Originally Posted by lionelhutz

EagleMark posted what Tunercat says, but the description is wrong.

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Hmmm... ? Your right! How does this look?

TCC Load Upper Limit Vs MPH, (Low Gears)
TCC Load Lower Limit Vs. MPH, (Low Gears)
These two tables contain the upper and lower load limits (%TPS) between which the TCC can be locked when in low gears. The TCC will lock when TPS% is higher then MPH for Lower limit. The TCC will unlock if the load is above the upper limit.

Quote:

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Originally Posted by EagleMark

These two tables contain the upper and lower load limits (%TPS) between which the TCC can be locked when in low gears.

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This line is wrong. The TCC could be either locked or unlocked between the limits. The 2 limits create the TCC control hysteresis. It's more like this. At the mph you are traveling, the TCC will lock when the %TPS goes below the lower limit and unlock when the %TPS goes above the upper limit.