A6 6L80E first/second gear issue...

[G8-4-speed]

I have two G8's that have had issues now with holding second gear. Both are 400+HP with 2800 stalls and both fall out of second gear under power. Has any one else had this issue or know a fix? The transmission holds the power fine initially but as soon and the rpm stop accellerating, it seems to drop line pressure and then the trans wont hold the gear anymore. Then when the rpm jumps, so does the line pressure and it grabs the gear again.

If you look at the scan, look for when it is in second at WOT. If you watch, the rpm flash's and the car accellerates then there is a couple rpm spikes. If you watch the MPH is isn't wheel spin. Also you can monitor the table display and see there is no commanding clutch for anything else to be happeneing. I have tried raising the base line pressure tables without and luck. Or maybe I just haven't put in the right number.......yet.......

[Bill@HPTuners]

Post the stock tune and last tune you loaded to the pcm.

[madvette08]

Is this happening while in Drive or in manual?

Ian

[G8-4-speed]

I am running a beta version of software and need to contact support at hptuners.com

[thesubfloor]

I have two G8's that have had issues now with holding second gear. Both are 400+HP with 2800 stalls and both fall out of second gear under power. Has any one else had this issue or know a fix? The transmission holds the power fine initially but as soon and the rpm stop accellerating, it seems to drop line pressure and then the trans wont hold the gear anymore. Then when the rpm jumps, so does the line pressure and it grabs the gear again.

If you look at the scan, look for when it is in second at WOT. If you watch, the rpm flash's and the car accellerates then there is a couple rpm spikes. If you watch the MPH is isn't wheel spin. Also you can monitor the table display and see there is no commanding clutch for anything else to be happeneing. I have tried raising the base line pressure tables without and luck. Or maybe I just haven't put in the right number.......yet.......

At what frame(s) do the RPM spikes happen?

[G8-4-speed]

Attatched is the stock file and the modified file.

The frame of the gear hold issue is 6170 and after. It is a persistent issue that doesn't "learn" it's way out of. I have more scans with the same thing happening but theres no point in posting. It happens above 400 ft lbs VCM calculated Tq, after the 4000rpm, and once the rpms level out(turbine accelleration slows down).

[G8-4-speed]

I am running a beta version of software and need to contact support at hptuners.com

Sorry, I couldn't upload the files and e-mail Bill earlier. the Network wouldn't support the large files.... from where I was at.

[thesubfloor]

Attatched is the stock file and the modified file.

The frame of the gear hold issue is 6170 and after. It is a persistent issue that doesn't "learn" it's way out of. I have more scans with the same thing happening but theres no point in posting. It happens above 400 ft lbs VCM calculated Tq, after the 4000rpm, and once the rpms level out(turbine accelleration slows down).

You have got MAJOR wheel spin issues which is more than likely the cause of the problem.

I've already gone through 8 transmissions in my 2007 Corvette as I drag race it quite regularly (over 200 times so far in just 2010) and the one thing that's most prominent about the 6L80 is they're notoriously fussy about wheelspin. If I don't hook properly when I launch the car I usually just get out of it as I know it's probably not gonna shift properly.

It also looks like you might have mechanical issues too based on the jaggedness of your RPMs. You might want to check out the scans in my thread from earlier this year which turned out to be two broken valve springs:

http://www.hptuners.com/forum/showthread.php?t=28474

I don't think it has anything to do with the calculated TQ values you're seeing either as my car runs low 10's and I'm making high 400's (TQ) to the rear wheels and usually cut high 1.4 60ft times.

The other thing I just noticed in your tune is that you have your upshift values way too close to your downshifts for both part and full throttle which can cause the transmission to get really confused.

As an example, in your "WOT Shift Speed vs. Shift - Normal" table you've got your 1-2 upshift and 2-1 downshift both set to 21. The general rule of thumb for this is to keep them at least 5MPH apart although I've noticed in the stock tune they're separated by as little as 2MPH in a few cases.

Hope all of this helps,
Christopher

[G8-4-speed]

The valve train is fresh and all my scan rpm lines look like that. But good observation. I have been through a few cams and went pretty crazy on spring pressure to look for changes in the scan. I recently added LS3 intake valves to my setup. Never seen any changes at any rpm.
I have tried an easy roll into 2nd gear and it will still drop in/out of gear without wheel spin. It does it at the track with drag radials. I thought I read something you wrote on the Vette forum about not changing the "max line pressure vs gear vs rpm". Since it will show an error when you try to change it back stock. Well, in either case that did happened. Not sure if it causes a problem or not. No matter what I set any of the line pressure tables, it will drop out of gear. I have the table display setup to show on-coming clutch and current gear. There doesn't seem to be anything "changing" of gear by the TCM but I don't have a PID to watch line pressure.

I really appreciate the tips and will give it a shot but this is the second G8 TCM that this is giving me a headache on. I have tried several drastic things on the other car. I tried dropping all the downshift points to the base downshift mph and it still did the same thing. The most recent had no issues until the stall converter was added. Didn't touch the tune and developed the issue.

What I have learned from tuning the A6 is when adding a stall, the TCM looses shift speed. I think the TCM watches turbine accleration to control line pressure. When the TCM see the big rpm flash from a stall, then the rpm acceleration slows down, is drops line pressue/shift pressure based on reduced rpm accelleration. Converters do soften shift but with the A6, it goes from crisp shift to sloppy shift and even flares with the addition of a converter. So there is more calcutions going on than we have control of as of this time.

[thesubfloor]

The valve train is fresh and all my scan rpm lines look like that. But good observation. I have been through a few cams and went pretty crazy on spring pressure to look for changes in the scan. I recently added LS3 intake valves to my setup. Never seen any changes at any rpm.
I have tried an easy roll into 2nd gear and it will still drop in/out of gear without wheel spin. It does it at the track with drag radials. I thought I read something you wrote on the Vette forum about not changing the "max line pressure vs gear vs rpm". Since it will show an error when you try to change it back stock. Well, in either case that did happened. Not sure if it causes a problem or not. No matter what I set any of the line pressure tables, it will drop out of gear. I have the table display setup to show on-coming clutch and current gear. There doesn't seem to be anything "changing" of gear by the TCM but I don't have a PID to watch line pressure.

I really appreciate the tips and will give it a shot but this is the second G8 TCM that this is giving me a headache on. I have tried several drastic things on the other car. I tried dropping all the downshift points to the base downshift mph and it still did the same thing. The most recent had no issues until the stall converter was added. Didn't touch the tune and developed the issue.

What I have learned from tuning the A6 is when adding a stall, the TCM looses shift speed. I think the TCM watches turbine accleration to control line pressure. When the TCM see the big rpm flash from a stall, then the rpm acceleration slows down, is drops line pressue/shift pressure based on reduced rpm accelleration. Converters do soften shift but with the A6, it goes from crisp shift to sloppy shift and even flares with the addition of a converter. So there is more calcutions going on than we have control of as of this time.

If you've change even one value in your max line pressure table with the beta version, the only fix (that I'm aware of at least) is to start off with your stock tune and then copy over all of your changes EXCEPT for the line pressure table. I did that with mine and have been fine for several months now.

If everything's set up properly there's no reason you should get either sloppy shifts or flare between shifts as I can actually break the tires free on my 1-2 shift as shown in the attached scan.

If you're able to recreate this problem easily on the street, take a scan and post it here. I'm still not quite sure what you mean by "drop out of gear" so hopefully another scan might help illustrate what it is you're experiencing. What I'd specifically like to see is an example of this but without the excessive wheelspin that was in the scan you already posted.

Although you might be lucky and have this be a fixable tuning issue, it almost sounds like you might have burnt up some of your clutch packs. If that is the case then you might want to consider your rebuild options....

[G8-4-speed]

If you've change even one value in your max line pressure table with the beta version, the only fix (that I'm aware of at least) is to start off with your stock tune and then copy over all of your changes EXCEPT for the line pressure table. I did that with mine and have been fine for several months now.

If everything's set up properly there's no reason you should get either sloppy shifts or flare between shifts as I can actually break the tires free on my 1-2 shift as shown in the attached scan.

If you're able to recreate this problem easily on the street, take a scan and post it here. I'm still not quite sure what you mean by "drop out of gear" so hopefully another scan might help illustrate what it is you're experiencing. What I'd specifically like to see is an example of this but without the excessive wheelspin that was in the scan you already posted.

Although you might be lucky and have this be a fixable tuning issue, it almost sounds like you might have burnt up some of your clutch packs. If that is the case then you might want to consider your rebuild options....

It will tear-up the tires on the shifts now but at first going from a stock converter to a stall the shifts get weak.

Look again at frame 6170, there is wheel spin to that point then the mph drops and the rpms still climb(clutch lets go) then at frame 6190 the clutch slams back on again and breaks the tires back loose(see MPH jump). When your driving the car is feels much worse than a little what you see on the scan.
Its like driving a 6 speed and pushing in the clutch and dumping it while at wot in thrid gear. The clutches are good, for now. It is a pressure drop. There is nothing commanding or clutches on-coming or off-going. I just don't know what to manipulate to get the results needed. Will try a few suggestions but I feel it will need flashed back stock with a Tech 2 first to get rid of the bug or maybe a newer Beta. Bill/Tech support is looking over things to see if there is anything they can do while I try not to break it in the mean time....

Appreciate you taking the time to look over the tune.

I bet if I lock the converter in second, it will hold second like a champ.......

[scottywheels]

cant lock them yet, HP Tuners says they are working on fixing it

[G8-4-speed]

cant lock them yet, HP Tuners says they are working on fixing it

I'll manually lock it with the Scanner.

[thesubfloor]

It will tear-up the tires on the shifts now but at first going from a stock converter to a stall the shifts get weak.

Look again at frame 6170, there is wheel spin to that point then the mph drops and the rpms still climb(clutch lets go) then at frame 6190 the clutch slams back on again and breaks the tires back loose(see MPH jump). When your driving the car is feels much worse than a little what you see on the scan.
Its like driving a 6 speed and pushing in the clutch and dumping it while at wot in thrid gear. The clutches are good, for now. It is a pressure drop. There is nothing commanding or clutches on-coming or off-going. I just don't know what to manipulate to get the results needed. Will try a few suggestions but I feel it will need flashed back stock with a Tech 2 first to get rid of the bug or maybe a newer Beta. Bill/Tech support is looking over things to see if there is anything they can do while I try not to break it in the mean time....

Appreciate you taking the time to look over the tune.

I bet if I lock the converter in second, it will hold second like a champ.......

First of all, I absolutely can't emphasize this enough - if you leave hard and without decent traction the 6L80 gets very confused and you cannot look at a scan to determine whether or not the car is behaving properly because all bets are off at this point. Until you can punch the car and not see wheelspin you are simply wasting your time.

What you're seeing around frame 6190 is the car shifting into 2nd gear and when it does, you're starting to get wheelspin again. I'm not sure if you realize this or not but your car does not go into gear at frame 6088 as that's just the TCM commanding the shift which doesn't happen until frame 6190.

Similarly, 3rd gear is commanded at frame 6213 but doesn't happen until frame 6223 and it's not coincidence that you start to get traction again because by this point your gear ratio isn't as high.

Something you have to realize is that 1st gear is already pretty steep in a stock 6L80 so when you throw a converter into the mix (even a 2800) it makes traction even more of an issue. To give you some numbers, a 6L80 with 2.56 gears is equivalent to a 4L60 with 3.73 gears. In my car as an example I'm running 3.42 gears which is equivalent to a manual transmission with 5.11 gears so to say that I leave pretty hard is an understatement.

I recently tried helping somebody with a supercharged 2010 Camaro SS who was having a similar problem as you and I told him quite simply that even if he flew me out to Tennesee and paid me $10,000 it is impossible to properly tune a car with a converter on the street since you can't get decent enough traction. Heck, I've even had trouble doing at a dragstrip with decent drag radials on some of the cars I've worked on.

I'm sorry if any of what I just wrote sounds harsh but I have logged a LOT of hours at the track so I know what works and what doesn't and the very first thing I noticed when I looked at your scan yesterday was the lack of traction and how you won't be able to figure anything out with those kind of conditions.

Oh, and if you try locking the converter in 2nd gear you'll burn up the lockup clutches before you know it because they're not meant for that purpose. I don't lock my converter at all at the track and I have no problems having it shift properly as long as I get decent traction.

[04blackgmc]

good info

[G8-4-speed]

The car ran 11.00 @126 w/6.5 lbs of boost and shifts perfect at the track. There is an issue with the max pressure vs gear table but its hard to tell if it actually has an affect on the max pressure. If you upload a modified table with "another" tuner, the 4000 and 7000 rpm tables will show up as "0" psi. BUT, it still shifts good at WOT so it can't be said that it causes the problem.

The trans ended up being a quart low and I added 1 extra quart which seemed to be the biggest fix for the problem. The transmission is very sensative when it come to fluid level. There is still a 2nd gear flare at light throttle when cold but I believe this is a clutch seal issue that is addressed in a TSB. We'll have to see if I can grease the wheels and get this fix at the dealership.

On my G8, I just added an 3/4 of a quart and the flare at high rpm went away.