8L90 Manual mode tuning(TUTD)
 

Just wanted to share some information for those looking to maximize their A8 performance when doing a roll.

What I have always found annoying with the A8 is that when going from a Roll, you either leave it in Drive and let the trans skip shift on it's own (which is slow if roll racing), or you put the shifter in manual mode, select the gear you want to do a pull in, then floor it, and move the shifter back to Drive (so the computer takes over). That works fine when you are stock or mild bolt-on but can be hit or miss when you start making more power and the car accelerates much quicker in the lower gears.

After the Whipple build, I found that when doing a low roll from first or second, the trans would no longer shift consistently from 1st or 2nd gear when moving the shifter from manual to D. The engine pulls to quick through the RPM band to make the shifts on time. It would either be short shift or touch the limiter. So I knew there had to be a better way.


I was on FB reading some posts by Brett @ PrayPerformance about Manual Mode Roll tuning. Then it dawned on me that we can edit the TUTD tables that control Manual Mode. If you look at these tables, each gear is set the same mph at all tps % to a number that the ECU will never see before reaching the REV limiter. So this means you have to manually command the shift. That is ok, but we all know the computer does a better job with the shifts. So I started messing with these tables and was able to get my transmission to shift at commanded MPH in each gear without needing to move the shifter over to D.

Here are the benefits of doing this.

1) The ability to leave the gear selector in manual mode without worrying about moving the shifter back to D to let the computer shift.

2) Now you can modulate the throttle if the tires are spinning and the computer will not short shift. It will stay in the same gear until X mph is reached to command the shift.

3) No more forgetting to move the shifter back to D after doing a burnout and hitting the limiter after launch because you forgot to move the shifter back to D.

4) Much easier to dial in the shift points and get consistent shifts because you don't need to off set with a bunch of lead time in gears 1 & 2.

5) You still can enjoy manually shifting the car for spirited driving just like before, the only difference is once you reach commanded MPH the Trans will shift on it's own.

Below are pics of the Stock TUTD settings( Pic 1-3) vs My TUTD settings (pic 4-6) for reference.

I tried this exact thing and wasn’t able to get it to shift. I dropped the numbers pretty low with no luck.

I was able to tune out 1st in the manual mode which I wasn’t able to do in the auto modes.

My process for racing at the track is keep it in manual mode for the burn out and launch then slap it over to auto. This gets me a 2nd gear burn out and launch without touching the shifter.

Then you did something wrong because it works well. 3 tables need adjusted for it to work. Brett has been doing this for his customer's tunes for a while now.

I hope you are right, I will look at my tunes when I get home. I do know the 17’s are flaky with the trans stuff unless it is just a problem for me. You can’t do a read and see what is in there.

That is odd...

One thing I had to make sure was all 3 tables lined up perfectly.

I need to send my TCM out and stop slacking. No excuses now that cooler weather is upon us. I can’t say thanks enough for sharing. I probably have enough of your shared information to fill a 2” binder.

No problem! :)

This is good stuff. Nice job!!

Thanks!

Now to get this working on my I4...

I have set 3 tables and mine doesn't shift either. Do you have TUTD enabled by chance? Mine is disabled.

Attachment 1015326

That's disabled on mine too. The changes worked for me. I can slap it over into manual mode, take off from a dig and it'll shift automatically into 2nd at 33mph (which is what I have it set at).

Thanks for the reply.

I think that mine was working the whole time with the settings from KingLT1. I was just uneasy about the high rpms. It showed 6700 rpms when it was performing the shift on the log. Also not sure the transmission was completely warmed up. Had 200 rpms of TCC Slip. I had the settings at 62 and 6300 rpm. It was actually shifting at 62 and revving all the way to 6700 rpm on the shift. I let out of the gas when it got to 6500 rpms. I just saw 6700 rpm on the log and thought it wasn't working.

I just changed 1>2 shift to 33 like yours and 2>3 shift to 60 and 6200 rpm and it shifts much better for me. When it shifts now, it only gets up to 6475 rpms. Can adjust later when I am more comfortable with it.

Thanks again

Yep....You need to command the shift early, especially in 1st gear. At WOT, I command the shift at 33 mph, but it actually shifts at about I dunno 36-37mph not really sure, but the RPMs are around 6700-6800.

Use MPH to set your shift points, not RPMs. And command it before you actually want it to shift at. The shifting looks at MPH first. Example..you said you have your 2>3 shift at 60mph and 6200 rpms...and you saw it rev to 6700. that 6200 meant nothing.

Thanks, that all makes sense now that you explained it. Was worrying about the RPMs for nothing.

Makes me wonder why GM wouldn't program the manual mode like this from the factory. Seems like it would be better than forgetting you are in manual mode and not shifting. Seems like it would be easier on the motor.

I agree. The stock setting bounce you off the limiter. Pretty dumb.

Because it is an actual manual mode that way. You guys have turned it into max performance auto mode.

This is Beautiful. Especially since I'm a little older (forgetful). And my new 2019 has no warranty whatsoever from GM. I think I need to have a diligent listening ear with some of you to get advice what you would do all over again if you had a new ZL1 with no warranty.... I will say that the company I bought the ZL1 from is giving me a 1 year warranty on them. So I won't make too many obvious mods from the get go. But after a year when I know the car is solid. I want to bring in a few (hundred) more horses.

Has anyone figured out how to make these TUTD edits to the T93 TCM?

That TCM is currently unsupported by HP Tuners, so no way to flash it until they do.

Any of you do any tuning with the truck OS? I have TUTD working on my 68 but it won’t tapshift at WOT using this method or manually shifting, shifts immediately and fine at part throttle. The reason I mention the truck OS is because when I’m in L gear to access the TUTD mode (different from cars) hptuners says my driving mode is in “normal” mode, not TUTD. With mine being a swap project I could be an oddball, I’ll need to do some testing on my wife’s Tahoe to see what hptuners says for driving mode when I use her TUTD. Either way just wondering if anyone has successfully figured this out for trucks. I’ve checked some truck forums and such with no luck.

8l90 Manual Mode tuning, burnouts
 

Have you had any issues with burnouts? Mine is jumping from 2nd to 3rd, then "D" drive, then neutral all in just a couple of seconds or less, (on its own)? Impossible to do a proper burnout. Launches and shifts down the track well. I know its been a while since this post, but any thoughts?

We've solved the T87a/A10 (2020+) tuning issues and can launch in first or second gear, and it shifts at set shift points automatically while in Manual. The car is faster with 1st gear launch. I drive thru the box and burnout in 2nd at around 5k rpm. No jumping from gear to gear. All runs have been with nannies off, but I'm going to leave nannies on next trip.

No issues...The problem sounds like your foot is too heavy. You don't just floor it to do a burn out. If you are going to do a second gear burn out then you need to modulate the throttle to keep it under the commanded shift MPH.

Put in manual, pull up your HUD, give it a little throttle in 1st to start tires spinning, shift to 2nd, spin them for 3 or 4 seconds at ~5k, let off and roll forward.

No you don't shift during a burnout with these transmissions. It's hard on them.

It is fine if you shift at a lower RPM. It's when you take it up to 6K+ and then shift during a burnout that really beats on them. I start in second, take it up just enough to get the tires turning, and then go to third to finish the burnout. It takes WAY too long to get a proper burnout in second gear.

Yea, I can see starting in 2nd and quickly shifting to 3rd.

I agree with that.

@KingLT1

Turns out the trans tune you helped me with already had the TUDU 2nd gear launch set up, but the shift points were too high for me still for 1-2 and 2-3. I assume because of my looser converter. So I just made the TUTD match what I had for WOT shift mphs and it works great!

:happy0180:

I am curious about a couple things with this as I am starting to do some tuning on my 21 ZL1 A10. I have read in one place that both the RPM table and the MPH table have to be fine tuned due to it looking at both tables and both have to be satisfied before it will shift. I have read in this thread that the RPM table doesn't matter, and just the MPH table needs to be dialed in. Can anyone clear that up?

Anyone care to share their MPH tables? Currently I have my set to upshift at...

1>2 32mph
2>3 58mph
3>4 84mph
4>5 99mph
5>6 120mph
6>7 149mph
7>8 181mph
8>9 250mph
9>10 280mph

It'll be a couple weeks before I'm able to test those speeds, so I was hoping to get some input before I load it in hopes of skipping a little trial and error.

The TCM must see both conditions (MPH First, then RPM second) to be satisfied before commanding the shift. So, if you set the WOT MPH shift point, do so just before the RPM you want it to shift at, because of the order in which it works.

Hmm. I loaded my tune and tried it out today but it did not appear to be following this logic. I had the Shift mph set to 58mph for 2>3 shift and RPM at 64
6,600rpm, but it appeared to shift at about 6,000rpm each of the 3 times I tried this. I will have to find a mph/speed/gear calculator to see what that works out to MPH wise as I didn't catch what the MPH was to see if it lined up with the 58mph or not. I guess it is also possible my tach was not keeping up at all, but unfortunately I wasn't logging it, so I can't go back and look.

Found a calculator and 58mph should be 6500, so neither of those really line up with the 6,000rpm 2>3 shift that i saw... I'll have to go back and look at my tune to make sure I didn't fat finger a number. I'll be sure and log it as I don't think it was the tach not keeping up. It sure felt and sounded like it short shifted too

Is there an learning/adaptive process that could be happening and may take a few drives to line itself out?