Need help understanding TCC Duty Cycle

I'm trying to better understand how to tune the max/ min TCC Duty Cycle tables. With the stock tables this is what I found.

First, I don't like the hard engagement of the TCC when it initially locks up, like when I'm getting up to speed from a dead stop to ~50 mph at about 15% throttle (light acceleration). It engages firmly and it just feels sloppy to me. :shrug:

Second, when I'm accelerating in 4th with the TCC locked (say when I'm getting on the freeway) I can feel the TCC slipping a little.

I tried setting the Max duty to 100 in all the cells. There was no slipped at all and I liked how I could accelerate with the TCC locked and not feel any slipping. However, when I did this the TCC engagement was very firm. I also tried it the other way around, now engagement is nice and smooth but the slipping under power becomes an issue. :doh:

Can you guys help me find a balance?

The factory scheme tries to enforce a finite low
slip RPM, the evident thinking is that you can't
servo to zero slip so get near-zero as a best
practical trade between economy loss in the
TCC frictions, and pump loss from excess pressure.

Naturally this brings in variation day to day, and
a higher chance that slip under load will be more
than you want (possibly even leading to P1870).

TCC duty is the last step in a pressure knock-down
chain. It delivers a % of the applied PCS (force
motor) line, straight-up (Force motor duty is upside-
down, a blowoff type valve, more current = less
pressure).

So even at 100% TCC, if force motor is blowing off
all line, you don't get much at the TCC.

TCC duty min/max are not the place for fine tweaking,
you need control over the duty vs torque profile, or
you work at it using the shift pressure, modifiers and
force motor table. I'd leave the TCC full on if you are
making decent torque, set & forget at 99%.

Of course my knowledge is only V8s and there may
be V6 nuances I don't know about.

well, I tried setting them at 100% and it was engaging VERY firm. Felt like a manual trans with a drop clutch.

You know what though, I think I may have solved the problem another way. The reason shifting into overdrive feels so sloppy at times is because the TCC is locked when shifting into 4th gear. (I can't imagine that being very good for it). So, what I did was disabled 3rd gear lockup and have the trans shift into 4th sooner while keeping the same lockup for 4th. Very smooth now.

For a V6 try setting your MAX table to 100 and MIN to 55. Raise your upshift and downshift speeds a little over stock and I think you'll like it. If TCC lock is still a little firm for your liking, drop the MIN to 50.

I'll have to try that too- you aren't kidding about how firm it is at 90%! Big difference vs a 4L60E!

sorry to bring this back from the dead but I have a 4t65e-HD car with a 3500 converter and when my converter tries to lock even under light load in 4th gear i have to let off the throttle a little bit so it will lock. Once its locked its fine but if i back off of the throttle to cruse it will unlock again... 3500 stall with 3.69 gears sucks on the highway with an unlocked converter

Copy of tune? We can help more than likely with a scan and tune bud. Make sure you are scanning commanded gear, shift commanded, input shaft speed and output shaft speed. And the normal stuff like RPM and such... a copy of your config will help us see what you see as well!

I'm glad someone revived this one I actually hadn't seen it yet and may finally be able to assist! If most of you experience this issue especially on higher mileage cars, a MUCH trusted GM Technician told me the *TCC Solenoid* can't keep up to the task a lot of times in the older vehicles. This could cause a slippage even in 3rd gear without the converter even set to lock up or not, simply because of how integral a torque converter is in/on an automatic transmission. Only while producing the sickest amount of power in 3rd gear "power band" have I noticed it, never from a low RPM dig, so I at least think that's what it is on my car. It's really just a rarely used family car, not a track car, never goes on the highway, and with the trouble you could get into if you drove it like that regularly, I've decided to slack and not fix it yet as we will rarely see this issue. But I promise to revive with a re-post with the results when I finally fix it.

*I'm 99% sure he had concluded TCC Solenoid, I will check with him, re-edit this post if needed and erase this amendment and all *'s soon.

Quote:

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Originally Posted by Dr. Nopps

I'm glad someone revived this one I actually hadn't seen it yet and may finally be able to assist! If most of you experience this issue especially on higher mileage cars, a MUCH trusted GM Technician told me the *TCC Solenoid* can't keep up to the task a lot of times in the older vehicles. This could cause a slippage even in 3rd gear without the converter even set to lock up or not, simply because of how integral a torque converter is in/on an automatic transmission. Only while producing the sickest amount of power in 3rd gear "power band" have I noticed it, never from a low RPM dig, so I at least think that's what it is on my car. It's really just a rarely used family car, not a track car, never goes on the highway, and with the trouble you could get into if you drove it like that regularly, I've decided to slack and not fix it yet as we will rarely see this issue. But I promise to revive with a re-post with the results when I finally fix it.

*I'm 99% sure he had concluded TCC Solenoid, I will check with him, re-edit this post if needed and erase this amendment and all *'s soon.

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Hey! I made an account on this forum just to reply to you. I'll be buying a tuner soon, but I wanted to say my 2000 Buick Regal GS has the same problem.
It was my GRANDMOTHER'S car, and slips the exact way you described.
I took it to GM as well, they confirmed - TCC solenoid.

Please let me know when you fix it and what options you chose. I'll be buying a tuner and this is all new to me :D

I can feel the TCC slipping a little.may be this is right!