6l80 WOT Slipping

[Cal Naughton Jr]

Using BlueCat to set the shift and TCC schedule on a stock Silverado/6l80 combo. TC is unlocked during shifts, raised oncoming pressures, and lowered WOT shift time to 3.4xx. First WOT pull and 1>2 was violent and may have slipped. Definitely had a rowboat feel, and the log isn't pretty. The shift time seems modest compared to others on the forum, so should I increase the pressures a little more? The log shows 2k rpm of trans slippage near the top of first, but it accelerated strongly the entire time. Stock truck and TM hasn't been touched. Ideas?

Silverado_6l80_WOT12.hpl

[GHuggins]

The 2300 rpm slip is 2nd gear engagement. Going to be 100% honest with you here. I kill tm 90some percent of the time on transmission side in the 6speeds then use the pressure and timing settings to control the shifts, BUT you can set the shift inertia settings higher and then make their corresponding timing settings lower under the shift timing tab. Honestly everything needs to work together, but the longer it takes to complete the shift the more it'll slip the clutches. Plus something a lot of people just don't seem to understand is that if the ecm or tcm see's something it isn't happy about, it'll still kick in torque management to complete a shift even if it is completely disabled. The engine side of the calibration will play into all of this with certain tables. The 100% row of the driver demand table for instance will aid in deciding what is used for torque management during the shift whether it be throttle or spark and how much of it will be used. Default trans settings on the engine side also controls the tm during shifts. Lots of things play into it.

[Cal Naughton Jr]

Thats a relief. Is that what you're saying caused the rpm dip at 3:59:29? I see tm pulled over 38* at one point. Just not sure why it was such a hard shift. Do you get your tune 100% before removing tm% or vice versa?

[GHuggins]

I start right from the getgo with all the 6speeds I tune but I have basic tuned tunes ready to go. If yours is pulling that much timing and dipping the rpms to complete the shift you really need to look into the shift timing settings and by those I'm referring to the settings all relating to the inertia settings. Unfortunately you can also have valve bind that will cause those same issues. This is really common with the 8 speeds for the 1-2 shifts for example. You can sometimes perform a scanner valve clean and then drop the pan and change the fluid to Mobil's then install a new filter and be good to go. Other times you have to replace the valve bodies, but again that's if you have that issue.

If you haven't seen it yet watch Cringer's 6l80 tuning video on youtube. Goes by SilverSurfer on there.

[Alvin]

Using BlueCat to set the shift and TCC schedule on a stock Silverado/6l80 combo. TC is unlocked during shifts, raised oncoming pressures, and lowered WOT shift time to 3.4xx. First WOT pull and 1>2 was violent and may have slipped. Definitely had a rowboat feel, and the log isn't pretty. The shift time seems modest compared to others on the forum, so should I increase the pressures a little more? The log shows 2k rpm of trans slippage near the top of first, but it accelerated strongly the entire time. Stock truck and TM hasn't been touched. Ideas?

Silverado_6l80_WOT12.hpl

Can you post the tune file?

"and lowered WOT shift time to 3.4xx" - This line doesn't make sense to me.. an appropriate WOT shift time target would be .15-.25

I strongly recommenced not removing TM from a 6l80. You can reduce it but you often don't have to reduce by much at all.

[Cal Naughton Jr]

After reviewing my tune, it seems I misspoke. Stock shift time was 3.4xx and is now 3.0xx. During the dip, I also noticed the PCS 4 Cmd Pressure had not yet reached 110 psi. Perhaps I didn't leave enough time to complete the shift and the trans and tm pulled the rpms down as it fully engaged?

BlueCat basically left WOT 1>2 stock, leaving the rpms the same, 5600, and raising the mph from 31 to 33. It blows past these conditions but still shifts at 5800 like I wanted. Other than torque adder timing and oncoming pressure preset, everything has been left stock, but it never shifted that hard.

Will definitely be giving SilverSurfers videos another watch.

[[email protected]]

I start right from the getgo with all the 6speeds I tune but I have basic tuned tunes ready to go. If yours is pulling that much timing and dipping the rpms to complete the shift you really need to look into the shift timing settings and by those I'm referring to the settings all relating to the inertia settings. Unfortunately you can also have valve bind that will cause those same issues. This is really common with the 8 speeds for the 1-2 shifts for example. You can sometimes perform a scanner valve clean and then drop the pan and change the fluid to Mobil's then install a new filter and be good to go. Other times you have to replace the valve bodies, but again that's if you have that issue.

If you haven't seen it yet watch Cringer's 6l80 tuning video on youtube. Goes by SilverSurfer on there.

I will second this, Cringer/SilverSurfer77 has some excellent 6L80 tuning videos on YouTube, he has a 4- or 5-part series. Well worth the time to learn how to do it correctly.

[GHuggins]

^^^^ Plus when done correctly, tm disabling won't hurt anything. People having tm issues with killing or hurting transmissions are usually still stuck in the high shift pressure mindsets. I constantly see people leave tm and then run shift pressures to the moon trying to complete a shift. Counter Intuitive if you ask me. With tm disabled my max shift pressure is around 1500kpa tops and just in select gears on stock builds. TM disabled plus high shift pressures, well things can start breaking if it just happens to bang in gear hard. If you tune in the shifts (completely and not just the final desired times) you can run with or without tm and be just fine. Like I've already pointed out - if the tcm or ecm either one sees something wrong causing it to not complete a shift it will still kill power to complete it. Part of the background safeties designed into them. I do advise if you go that route to go cautiously, but if you're using tm and it's still banging into gear after hesitating then you're already doing harm even using tm... You need to get the actual shift timings figured out then go from there. I agree the 3.something times don't make sense unless you're looking at the low torque input rows. Units on the left are Nm's - this is the delivered engine torque being logged that it's using to see what shift cell to go by during a shift.

[Alvin]

The reason to keep TM in a 6l80 or 8 or 10 speed has nothing to do with preserving parts.

They are synchronized type transmissions. It lets go of one gear before applying the next. If there is no torque management it is essentially power shifting every gear. Imaging shifting a manual around town never lifting off the gas. A 4l60-80 will apply the next gear and that will overrun the one before it. They exist just fine without TM.

[GHuggins]

TCM's logic usually watches out for all of that. Plays into the tm still being used even if it's entirely disabled I was talking about. I've never had one fail disabling it in the last decade that I know of, but I tune one in to a heavy extent. Also never had one try to engage 2 gears at once not to say it couldn't happen. Either way, if one doesn't want it entirely disabled, they can always dial it back. No biggie...

[Alvin]

There are long term issues with disabling TM.. Some of them around a year or two in they will start randomly missing shifts at WOT. It will feel like they shift to neutral instead of shift.

When HPtuners first started doing 6l80s (i'm thinking this was 2008-2010ish) all we had was shift pattern stuff and a master disable/enable for TM. Nothing else. No shift pressures, times,etc. It was during this time we discovered many needed touch ups. Furthermore I get a lot of work from guys who didn't get satisfactory tunes else where. The ones with the TM disabled I have to go back and relearn, clean, reset, and start over.

[GHuggins]

Maybe it's because of how I dial mine in that they don't have that problem? I know I've stayed in contact with a few customers over the last decade that I've tuned like that and even done bigger build mod tunes for them 4 to 5 years after the fact and they've never had or mentioned having issues with wot shifts and I always ask them how they were holding up and how the vehicle had been doing. Like I said though, I tune a lot in both on the engine and transmission sides. Only problems I've ever seen with shifts were the 8speeds for wot and even then it's the 1-2 and those have valve body 1-2 issues anyway. I've had 2 in the last 3 months with regular driving issues because of the valves sticking on swapped vehicles. Even normal driving with tm, as that's the only transmission I usually leave tm on with and they still have issues shifting, but again no other shift settings to adjust other than some final "wanted" time settings and pressures. Only solution on those is to lower shift pressures and hope for the best to keep the valve from binding.

I'll keep doing the 6speeds the way I do. If I see issues arise, I'll change it Just not a fan of lowering final desired and jacking pressures through the roof.

[Cal Naughton Jr]

Missed Alvin's comment before my last post. I was incorrect for a 3rd time, I misplaced my decimal. The only shift timing I've altered has been the torque adder parameter, which stock was set to 0.3496 at WOT. The hard shift was caused by changing this to 0.3057 and has been fixed by raising it to 0.3203. Crazy how these small changes can make such a significant impact.

I don't mind removing some tm but won't be removing it all. Silversurfer removed 50%, but then put it back to stock at a later time? Not getting crazy with it as this is a dd and not a race truck. It's also my toy hauler and I don't like that there's not a separate shift table for tow/haul mode. Reliability is my main concern.

I'm also wondering what the deal with TCC Adapt is. Stock has the Torque Min above the Torque Max, which seems strange?

Lastly, are there any significant gains to be had by running higher octane fuel? I'm sure it's a case of GM riding the knock line but raising shift points with BlueCat still gets KR at light cruising on stock timing tables.

Here's my current and stock tune

2015_FRFR_83.hpt
Stock_2015.hpt

[edcmat-l1]

When HPtuners first started doing 6l80s (i'm thinking this was 2008-2010ish) all we had was shift pattern stuff and a master disable/enable for TM. Nothing else. No shift pressures, times,etc.

I remember. I bought EFIlive back then just for the 6 speeds and the VVE availability as well. I did a lot of crossover tuning for a few years. Do a calibration with EFIlive and suck it back out with HPT.

I also do not remove TM. I modify it slightly but most of the time I keep it nearly 100% intact. Some pressure and shift timing changes and they all seem to work beautifully.

[edcmat-l1]

Lastly, are there any significant gains to be had by running higher octane fuel? I'm sure it's a case of GM riding the knock line but raising shift points with BlueCat still gets KR at light cruising on stock timing tables.

Absolutely. The reason the timing tables are so low is because they're set up for crap fuel. Put some high test in it and crank some timing in it. It'll help with load induced knock also.

[lippmoney]

Hats off to you real tuners who know and understand all of this. Reading these posts and responses is incredible to me - it's like a lifetime of another language that you all are speaking fluently like its no big deal. Bravo.

[MeshaalMMT]

having full TM on the trans side is very important.

[Alvin]

People hear torque management and instantly think of it as a nanny mode. We just need the power to let up a bit when you disengage the clutch, apply next gear. Just like a manual would do. Specifically because these transmissions do not shift like older 3/4 speeds. You can still get tire barking shifts with full torque management.


And 100% on the 93. Trucks pick up huge with tuning on 93. On 87 a lot of trucks especially 6.2's or late 5.3's will knock big time on the stock timing tables. If you have to pull timing to keep it from knocking than you also won't be picking up much with a tune.

[Cal Naughton Jr]

Good info, I'll get my wallet out for my next fill-up.

Since I'll be in the spark tables, I figure it'll be a good time to get acquainted with the VVT/VCP parameters. What's the general consensus on Desired Angle the low/med/high tables? I see some people copy the low table over to the med/high, and others zero the high table, and some zero all three. Then there's the VCP Spark, which most seem to zero and address in the main spark table. It doesn't seem anyone messes with the VCP PDA tables.

[GHuggins]

Again, it's because people don't bother to dial the tunes in. The PDA part is for swirl control. I don't worry about that as it may or may not even be used, but the variable cam spark is pretty important if you're utilizing variable cam for engine load and towing.

You want a general rule of thumb on where to start - take the mid table and cut the lower load below 3600 rpms in half then paste the whole into the high and low tables. Cut the cam ignition timing modder in half. I really recommend if you have the ability to do so do both highway mpg dial in for all of the tables then throw about 5000 behind her and finish it up.

Like I've stated even on the transmission stuff. TM is used whether it's disabled or not. I've been through these things heavily with tuning. I even disable tm on the vip ones I do which weight up to 15000lbs and if they were having problems, I would know.....