GM SuperMatic 6L80 - Unexpected 6-5 downshifts

[DrRJones]

TPS 37% cruising along, accelerate slightly as soon as I touch 107 mph the transmission will drop to 5th for no apparent reason, at least I cannot find a reason in the tune. I am pulling my hair out trying to figure out WTF is going on with this.
In the log at 7:44:35 is where it downshifts.
One other thing, during 3-4 shifts at the beginning of the shift for a split second it feels like a trans brake is applied before it completes the shift.
Its really hard to see that in the log.
I have adjusted Oncoming & offgoing pressures, shift timing, shift scheduling every way I could and nothing seems to help. I was wondering with the "SuperMatic" could it be the "oncoming volume presets"? The SuperMatic is supposed to be more robust the a regular 6l80 as far as handling a higher torque input. So if there are added clutches to accomplish this then there would be less capacity for fluid. I'm just guessing at this point.
Hoping someone would be kind enough to take a look at my tune and log and possible find something I am missing.
Thanks in advance to anyone that takes the time to look.





1984 El Camino N/A 408 Iron-Block LS3 Terminator X Max SuperMatic 6L80

[hjtrbo]

The downshift to 5th needs a binary edit to fix. Myself or trecool can do it for some beer money.

The 3-4 shift is normally very smooth, even with aggressive settings and high power levels. I'm not seeing any torque management being applied during shifting in your log (the trans torque PID value should dip like a square wave during the shift). In your tune file the torque management upshift setting is blank (TCM 421), any idea why? I'm not familiar with the Supermatic variant.

Add input and output shaft speed channels - set polling to 50hz (right click channel)
Add PCS channels - set polling to 50Hz
Add TCC slip and pressure channels - set polling to 20Hz

[DrRJones]

Thx hjtrbo for taking a look..!
A binary edit, I?m guessing you have seen this behavior before. How much beer are we talking about here? I like beer too
The TCM is a T43 maybe that?s why the torque management upshift setting is blank.
The ECM is a Holley ?Terminator X Max? from what I am understanding the TCM only sees TPS & RPM and does not interact with it therefore engine torque management isn?t possible. I believe this is because there is no VIN associated with the TCM and the Holley ECM doesn?t know what to do with it.
The BACK STORY:
All of that was unknown when I bought this SuperMatic. Once the 6l80 was installed and I tried interfacing with it using the Holley 6l80 trans tuner addon for the Terminator X which errored out on me.(https://www.holley.com/products/fuel.../parts/558-499)
That?s when I discovered the 558-499 could not identify the transmission application due to no associated VIN. Ultimately I had to use the tuning software that came with the transmission to get a canned configuration installed so it would actually operate, this software which is by the way a big POS and very limited in what it can change or adjust also it used terminology that didn?t correspond with anything mainstream that made sense to me.
I reached out to Holley & GM then to Zero Gravity Performance Who supposedly wrote the code for the T43, was then told you have to use the OEM software that?s the only way to tune the ?SuperMatic 6l80? because of it?s special build and must have the E38 ECM to get it to operate or ?it ain?t gonna work? ?
Not convinced with that I broke out my HPT
and lo and behold HPT didn?t give a shit about a VIN I could see and interact with the 6l80 so this is how I got to this point.

All in all is performing quite well, except for those two issues.

Before I go to work this morning I?ll get these setup (PCS not possible) to log while on my way to work (50 minutes) and post the results later this morning or afternoon, what ever time allows.

Add input and output shaft speed channels - set polling to 50hz (right click channel)
Add PCS channels - set polling to 50Hz
Add TCC slip and pressure channels - set polling to 20Hz

[hjtrbo]

You need torque management working. If the Holley unit is unable to do it then I strongly suggest to use another product. You will kill the box without it.

I had a look in your file, the vin is supposed to be in 4 places but all of them are blank. The upshift torque management flag has been set to 0xff. That's why it shows up as blank. The address is correct though.

No idea why the vin matters to the Holley unit. All it should need is the OS part number???

I haven't tried SPS on a standalone system like yours but it might be worth looking into to get a factory cal back into it. Based on your comments, the Holley might do what it's supposed to.

Any reason you can't run an E38? They're cheap as chips.

I won't go any further with you till the torque management is working and I don't know anything about the Holley unit. Sorry

[Alvin]

TPS 37% cruising along, accelerate slightly as soon as I touch 107 mph the transmission will drop to 5th for no apparent reason, at least I cannot find a reason in the tune. I am pulling my hair out trying to figure out WTF is going on with this.
In the log at 7:44:35 is where it downshifts.
One other thing, during 3-4 shifts at the beginning of the shift for a split second it feels like a trans brake is applied before it completes the shift.
Its really hard to see that in the log.
I have adjusted Oncoming & offgoing pressures, shift timing, shift scheduling every way I could and nothing seems to help. I was wondering with the "SuperMatic" could it be the "oncoming volume presets"? The SuperMatic is supposed to be more robust the a regular 6l80 as far as handling a higher torque input. So if there are added clutches to accomplish this then there would be less capacity for fluid. I'm just guessing at this point.
Hoping someone would be kind enough to take a look at my tune and log and possible find something I am missing.
Thanks in advance to anyone that takes the time to look.





1984 El Camino N/A 408 Iron-Block LS3 Terminator X Max SuperMatic 6L80

I've only done one of these supermatics before. My thoughts were they worked nothing like a OEM TCM. I don't think you're supposed to be able to tune it with Hptuners it just happens to work.

I was able to do the car I was sent but I was never able to undo how harsh the TCC applies. I can't remember if I tried turning TM back on. They do wierd things. Like not moving after a reflash.

[DrRJones]

The Holley ECM will do TM if it knows what application the transmission is, I'm assuming that info comes from the VIN.
My fuel system is a Holley 4150 throttle body, The E38 is not going to work.
Is it possible to apply a VIN to T43 TCM if so then I would think TM would be operational on the ECM. Thoughts?? BTW this morning log is attached. if you wanted to look at it.

[DrRJones]

I looked at the up-shift TM and it was truly blank as in the attached pic. I did have the option to enable it. hjtrbo do you mind taking another look at my updated tune and see if it is actually enabled. If it is I bet TM would work.

Thx

[hjtrbo]

Yep, it's enabled. Worth a shot for sure.

[hjtrbo]

The Holley ECM will do TM if it knows what application the transmission is, I'm assuming that info comes from the VIN

I'd be floored if that was the case. It should just be able to lookup the OS part number.

My fuel system is a Holley 4150 throttle body, The E38 is not going to work.

That answers that question. Kinda sux because you won't be able to have the rev match feature on tap downshifts. Not a biggie, but it is a cool feature to have.

Is it possible to apply a VIN to T43 TCM if so then I would think TM would be operational on the ECM. Thoughts??

Not done easily, need to workout the 4 locations. Then need to determine what if any checksums need updating. Can be tricky as the algo needs to be known.

The beer money keeps going up lol, you'll be filling my fridge at this rate

[Tre-Cool]

late to the party, at least the trans os is based off 24256125. I would just do a segment swap from an 2010/2011 hsv. reset the adapts, set your relevant tyres/diff size.

the shifting back to 5th would be highly likely related to your high 4.10 diff gear, ALL 6l80's have a maximum output shaft rpm speed, which forces the 6th to 5th downshift.

none of the software on the market has these mapped out, they are not hard to find & i've posted the location previously on the forum.