TCC apply/release values in stock 6T70 tune

I have a 2012 Impala with a 6T70 transmission and have a few questions about the stock TCC apply/release settings that don't many sense to me and wanted to get some input from others with more experience.

First, from what I've read, the TCC apply values should *always* be higher than the TCC release values. However, in the stock tune I've noticed this:
- In the part-throttle tables, the 4th gear apply value is "6" at 0% throttle, while the release value is "30" at 0% throttle?
- In the wide-open throttle tables, the 2nd gear apply value is "12", while the release value is "311".
- In the wide-open throttle tables, the 6th gear apply value is "93", while the release value is "96".

All of these seem to break the "apply value should also be higher than the release value" rule. So what really happens in those situations? Are they errors in the stock tune?

Also, I've noticed that the wide-open throttle tables do not always match the 100% throttle values in the part-throttle tables. Shouldn't these always match? If they don't match, what values are actually used at 100% throttle (which I'd assume is the same as "wide-open"?)?

Thank you! Just trying to understand these "inconsistencies" in the stock TCC apply/release speed tables!

The stock TCC tables are a mess. Check out the trans tune I did in this thread for some tips.

http://www.hptuners.com/forum/showth...eds-fresh-eyes

Russ Kemp

Ok, I'll check it out. Thank you very much for the reply, I appreciate it!

So I just took a look at that tune file, but it appears that the TCC lockup is completely disabled for gears 1-4 (apply and release values are all set to 318).

Also, the WOT apply/release values for 5th gear, @ 100% throttle (in "normal" tables) is 160/113 - while it's 318/318 in the WOT table for 5th gear. So in this situation (where they are different between "normal" 100% value and WOT table value) which values would be used - the "Normal" 5th gear, 100% values or the WOT 5th gear table values?

Also, what happens if the apply value is lower than the release value (like it is in certain situations in the stock tune)?

Thank you!

Yes, I disable TCC lock up until 5th gear, as it prevents the engine lugging at lower speeds. You want the TCC to lock slightly higher than the trans upshift, and the TCC to unlock slightly higher than the trans downshift. So the TCC might lock in 5th gear if you hit 160 MPH, if your car went that fast, then raise the 100% TPS lock up speed. But I believe the WOT apply speed would prevent the TCC lock up at WOT regardless of the normal table speeds.

Russ Kemp

Thank you very much for the explanations. I'm very new to all of this, so I really appreciate the assistance while I try to understand this stuff. I do understand that I would never actually go 160mph in this car, but I was just curious about the "theory" part of it (whether it would use the gear 100% throttle table setting or the gear WOT table setting at 100% throttle - if they different).

I do have a few more questions for you (if you don't mind - you've been extremely helpful!):
1. What happens if the TCC release speed is higher than the apply speed?
2. What happens if the TCC apply and release speed are set to the same value?
3. Are there any other significant "side effects" of disabling the TCC completely in gears 1-4 (higher trans temps?, fuel efficiency changes?, etc)
4. I'm assuming that the "throttle %" in these tables is the pedal-throttle percentage and not the actual throttle percentage (which would never reach 0%) - is that correct?

Unlike most performance guys, I'm looking for very smooth, comfortable shifts - my goal is to make the shifts as un-noticeable as possible. Most performance guys seem to like the fast, "firm" shifts (which are extremely noticeable!) - which I don't like - it's a daily driver, not a race car - I don't ever try to see how fast I can get from 0-60mph, etc - I prefer comfortable, seamless shifting. Any tips on what to change to make the shifts as seamless and un-noticeable as possible? Should I keep the TCC locked as much as possible or unlocked as much as possible for my goals - or doesn't it really relate tp what I'm looking for?

Again, thank you very much for spending the time to answer my questions - it is very much appreciated!

Changing the TCC tables isn't going to have the desired effect you're looking for, though it may reduce some drivability quirks. If you want smoother shifts, you'll have to play around with the shift pressure tables and desired shift torque tables. I'm at work right now, but when I get home later I can show you what I'm talking about. I'm also tuning a 6T70 right now. In the mean time, can you post your stock tune?

Russ helped me out too, he's awesome.

Well, I guess let me explain the history of things a little. Since I purchased by 2012 Impala (with 19k on it when I bought it), I've never the liked the way it shifted. Low-speed shifting was horrible (jerky/clunky) and shifting overall was just "inconsistent". I ended up buying a mailorder tune from a well-respected tuner (@Overkill, if anyone is familiar with him) and it actually made most of my shifting-related complaints even worse - the shifts were much too "firm" for my tastes and I still had strange shifts (I call them "WTF? shifts"!)... I did like the engine tune though (3.6L LFX engine) as it made the throttle more usable and more natural. So I then started to do some research and am trying to customize the transmission tune to my liking. I'm not concerned with increasing the performance of the car (it's 300HP stock, from the factory, which is plenty for me) - I just wanted a more comfortable, more natural driving experience. This is my first 6-speed, by the way.

Anyway, after doing some research, I ended up reverting most of the @Overkill transmission part of the tune back to stock and I'm trying to change this here and there to make it more "comfortable". I'd like to get rid of the occasion "WTF? shifts" and keep the shifting as smooth and un-noticeable as possible. So far, I've found that disabling "neutral skip shifts" helped get rid of some of the "WTF? shifts". I have a feeling that the TCC apply and release speeds are the cause of some of the remaining "WTF? shifts" (since they sometimes feel like a shift) - which is why I'm trying to tune them.

My understanding is that you should never need to adjust the line pressures on a stock transmission - especially since these transmissions have the "adaptive learning" function - which should account and adjust for "normal" wear-and-tear...

So that's my story and why I'm here! :-) I can't post my current tune because the majority of it is a mailorder tune. My stock tune is posted in the repository....

Thank you!

I don't put much stock in their "adaptive" programming. Adjusting the pressures is the most direct route to changing shift feel. Besides, the manufacturer will tell you not to adjust anything about the car from stock, and here you are on a tuning site!

Can you be more specific about "WTF shifts"? Like is the car downshifting into really high revs unintentionally? I noticed the stock 3-2 downshift speed table is poorly done. It would be easy to downshift hard into 2nd gear from 4th or 5th at moderate speeds when you might have only wanted modest acceleration power. My stock trans table had a mistake that lead to a clumsy 6-4 downshift any time you called for acceleration on the highway and it annoyed me enough to drive in manual mode.

My two suggestions for making the shifts more smooth and comfortable are to decrease shift pressure by 30-50 on the Base Shift Pressure Upshift and Downshift tables and lower the values on the Shift Inertia tables by 2-4, with the lowest values being 1. It's not gonna hurt anything, see how it feels and adjust from there.

These are the tables I'm talking about.

http://cp-the-nerd.com/images/Shift_...Screenshot.jpg

http://cp-the-nerd.com/images/Shift_...Screenshot.jpg

Sorry, I wasn't very clear in my last email...

When I said that it wasn't normally recommended to modify the stock line pressures, I meant that it generally wasn't recommended by other tuners (of course the car manufacturer wouldn't recommend that!)... Most seem to say that it's better to modify the speed of the shifts and not the pressures. Here is an excellent transmission tuning guide posted by another forum member - different type of transmission, but same "theories":

http://www.hptuners.com/forum/showth...CC-TM-(w-Pics)

Since reverting back to the stock value for the shift speeds (how fast it shifts, not the shift points), the shifts are actually comfortable enough again - just need to address the "WTF?" shifts. My "WTF?" shifts are shifts that seem to occur at "unnatural" times or when the car seems to be "confused" and doesn't know which gear it wants to be in. I actually took my laptop with me during a drive to/from work one day and placed 3 markers in the log where I experienced "WTF?" shifts. After reviewing that data, it consistently seems to happen on 4th->5th gear shifts around 40mph at low throttle. I'm thinking that "strange" shifting may be TCC related.

I'm going to try removing the TCC lockup from 4th gear and see if that makes any difference. Here is the log file I'm referring to. There are (3) markers listed at the top - the "WTF?" shifts are usually a few seconds before the markers and there is always a 4th->5th gear shift right around the markers. Unfortunately, I don't seem to be able to log the TCC lockup status (should I be able to?). I was logging the TC slip rpm if that helps...

If anyone can view this log file (around the marker times) and let me know what they see, if anything, that would be a huge help!

Thank you.

Crap - can't seem to upload it (it's a 15MB .csv file - too big!)... Was going to just upload the .hpl file, but it's also too big (4.8MB)! I can email them if anyone is interested it looking at them...

I understood you, I was mostly being tongue in cheek. The 4L60/65E trans is MUCH different than the new 6-speed and requires a different approach for tuning. Chris@HPTuners has several informative threads about the GM 6-speed automatics including the 6T70 that explain this. Decreasing shift pressure where it's harsh is not going to potentially decrease longevity like maxing out pressures for faster, more crisp shifts.

When I was tuning my 6T70, changing shift time had very little effect on feel. The single most effective change was altering the pressure. Worst case scenario, you try it and don't like it, then you can return pressures to stock.

Let us know how it goes when you alter TCC lockup. My driveability issues in the Malibu were all related to trans shift-speed tables like I described. The throttle was dialed so far back that the car would bury itself in high gears and refuse to drop out, which caused too little spacing between gears and would drop two gears when you only needed one.

Now that is really strange. I completely understand that tuning the newer 6 speeds is completely different than the older 4 speeds, but even my mailorder performance tune didn't touch the line pressures. Just by changing the shift times and minor TM changes, it had a huge impact (mainly the shift timings - shifts were much "firmer" - in fact, too firm for my liking - but the performance guys love it!). It's not just that one guide that mentioned that you typically shouldn't change the line pressures on a stock transmission - I've seen it in multiple places - especially since the adaptive system will just try to get it back to "normal" anyway (in fact, I've also read that you really need to disable the adaptive learning while tuning the line pressures on these transmissions because the adaptive learning just tries to re-adjust anyway). But I honestly don't know either way - just basing things on what I've read from other tuners.

Anyway, I'll try disabling TCC lockup in 4th gear and see how it goes. As of now, I'm fine with the pressure settings - it's just the occasional "strange" shift/tcc-lockup issues that I need to address - the "firmness" (or lack thereof) is fine with the stock shift time settings.

Thanks!

EDIT: Ahh... Apparently, even though we have the same transmission (you have a 6T70 you said, right?), the transmission shift time tables are very different. You have tables I don't and I have tables you don't. My tune changed the shift firmness via "Shift Time Torqu Adder" settings - I don't even have the shift time settings that you do... Not sure what is different between our transmissions, but something is very different...

EDIT2: My research shows a 2009 Malibu having a 6T40, not a 6T70... Might be the difference...

EDIT3: Sorry, looks like the 4-cylinder version is the 6T40 and the 6-cylinder is the 6T70 - so not sure why the transmission tables are different...

JT, I would try disabling the TCC lockup in 4th gear, and then enable it in 5th gear only above 45mph, see if that helps. You may use a little more fuel in the 40-45mph range under cruise since the converter will free-rev rather than being clutch locked

I had already disabled TCC lockup in 4th and it definitely seems much better... I am currently using the stock transmission settings though. Honestly, I'm not sure how to properly set the TCC lockup table speeds for 5th and 6th gear on the Overkill tune - could you shoot me an updated tune with the TCC lockup speeds for the 5th and 6th gear - that would be a huge help!

Thanks.

The trans tables are different because your final drive ratio is 2.44 versus 2.77 in mine, so each gear redlines at a higher speed than mine. The reason is fuel economy, though 2.77 is already pretty damn tall, but whatever.

I didn't mean that the table *values* were different, I meant that the actual tables themselves are different. For example, under Transmission->Auto Shift Properties->Shift Time, I don't even have the Base Upshift or Base Downshift time tables at all! My shift times are changed mainly with the "Shift Time Torque Adder" tables. I'm also missing some of the "Inertia" tables that you have.

I guess they are just different versions of the controller software. Changes to my "Shift Time Torque Adder" tables make a very big impact in the firmness of the shifts (without messing with the line pressures at all). I just found it strange that there were entire tables missing for my car that you had being that it's the same transmission...

Quote:

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Originally Posted by jtrosky

I didn't mean that the table *values* were different, I meant that the actual tables themselves are different. For example, under Transmission->Auto Shift Properties->Shift Time, I don't even have the Base Upshift or Base Downshift time tables at all! My shift times are changed mainly with the "Shift Time Torque Adder" tables. I'm also missing some of the "Inertia" tables that you have.

I guess they are just different versions of the controller software. Changes to my "Shift Time Torque Adder" tables make a very big impact in the firmness of the shifts (without messing with the line pressures at all). I just found it strange that there were entire tables missing for my car that you had being that it's the same transmission...

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Ah, I did notice that when I was looking through the stock Impala tune. I'm not sure what that's about. Other GM vehicles with FWD and RWD 6-speed transmissions match my table layout almost exactly. Maybe contact support about it and see if there are issues with the Impala PCM read.

Just to follow-up about the "missing" tables in the transmission section of my 2012 Impala. I checked with HPTuners support and the tables are not really "missing" - GM just changed the way that the newer 6-speed transmissions are tuned (both FWD and RWD). For example, the newer Camaros have the exact same transmission table layout as my Impala. So, like I said earlier, even though we both have a 6T70 transmission, the methods used to tune certain things on them are apparently very different.