3-4 shift 6l80E track only...

[thesubfloor]

It's well documented on Corvette Forum, at least for all LS2 C6's, not sure if it's an issue with LS3's. If you use paddle mode to do a burnout and simply go to D and back to S mode, you will get hesitation through your shifts at WOT.

The solution is to cycle the shift lever all the way through Reverse and back, then stage and launch. I personally saw the problem duplicated and resolved in 3 C6's at the track and with at least another racer online.

That being said, this issue was found before 2.23 was released so I don't know if all the new trans settings changed anything.

That might explain it then, as I use the paddles for the burnout but stay in D for the run.

[morgan72]

Interesting to note that when i had those 2 clean runs as well on my last track visit, , there were hot laps as well, the track was about to close, and i was about to cry after changing crap up in the tune for 8 runs with no luck. i went to eat, made the change, loaded the new tune, and drove straight to the track, didn't park the car to allow the engine to cool down or anything, i just drove straight to the staging lanes and did my first run, no issues, went at it again inmediatly after that one, no issues.

So is there a timer in the tune, or is it a mechanical issue. I was think that maybe it could be a low fluid issue, but I'm not sure. So I was thinking, if I hot lap the car, turn it off and start it back up before making the 2nd pass, I would know if it is a computer or mechanical issue. Not sure where I would go next. I really want the car to be cooled down and have the trans work at the same time.

[C5pilot]

So is there a timer in the tune, or is it a mechanical issue. I was think that maybe it could be a low fluid issue, but I'm not sure. So I was thinking, if I hot lap the car, turn it off and start it back up before making the 2nd pass, I would know if it is a computer or mechanical issue. Not sure where I would go next. I really want the car to be cooled down and have the trans work at the same time.

A tuned (with 160 stat) LSx engine will run faster at lower temps, but hot trans fluid reduces drag.

[04blackgmc]

i think the hot lapping is because it has seen a 1-2 2-3 3-4 shift ... when u shut it down and restart the car it hasnt seen those shifts during that run time..

this was my reason of thinking and why mine has yet to EVER do this to me on the street.

i havent been back to the track to see if hot lapping fixes it plus the local track is so damn busy.

[LSX378]

A tuned (with 160 stat) LSx engine will run faster at lower temps, but hot trans fluid reduces drag.

Hot trans fluid also sees clutches empty and fill a lot more quickly.

They run real nice at around 220-230 deg trans fluid temp.

[ArklaTexan]

Hot trans fluid also sees clutches empty and fill a lot more quickly.

They run real nice at around 220-230 deg trans fluid temp.

I thought you want to keep the transmission temp under 200! Is the data i am reading off my aeroforce gauge fluid temp for the trans?

Also I am trying to fix the lag issue on the 3-4 shift. I am trying to make a great track tune for transmission and then load in a conservative DD trans tune when I leave. Any help is appreciated. I have a 2008 G8 GT with TVS1900 and a 3.2 pulley putting down 508rwhp. I still have stock cam and DOD garbage. Is 6500 ok to shift with these transmission at the track. I want to go higher but I cant risk hurting it.

[johnh]

My 2 cents...I wouldn't shift point any higher than 6200. By the time it shifts you'll be in the 6200-6400 range...

So you can modify the TQM so that there's less TQM at higher RPMs. This works pretty well to keep the cruise light thottle shifts smooth and soft, yet when you go WOT you can break them loose. If you really want to go all out and don't mind the transmission wear, make your track tune with upshift TQM disabled and/or reduce the shift times.

Personally,

I'd set it up where its only shifts hard at higher RPMs, leave the TQM enabled. If you want to play with the RPMs, don't forget you can use sport mode for the higher rpm settings.

[bluegoat06]

I was casually reading the other day at another guy personal website that modern transmissions have some sort of diagnostic checks that when the engine is started/restarted and inmediatly put through its pace,those tests can affect how the trans shift at WOT.

The guy was commenting about his A6 Corvette and how the 2-3 shift would be delayed at WOT after a engine restart costing him ET and traps. he mentioned the only way he found to prevent this from happening was to run the car above 20mph prior to the track run. i've been looking for the link but i cannot remember where i saw this.

Chris@HPT, you think you could take a look at this in your free spare time ? i know you're extremely busy, but it would good to know how can we prevent this from happening with a table in HPT, or maybe you could find something in there that at least tell us to drive the car above a certain mph letting her go through an especific shift sequence or something. hot lapping seems to work, but i know at our local tracks hot laps are impossible given the number of cars racing. so we have to shutdown after every run and wait for the next round.

[04blackgmc]

everytime i hot lap mine it shifts perfect... most the time i have to sit in the pits for 30-60 mins fans on high and hood up and just idle...

sucks but the 3-4 works when i dont turn the car off...

learned all i have to do it go part throttle in the parking lot and pull into the lanes (as long as the car sees a 3-4 shift)

[ArklaTexan]

everytime i hot lap mine it shifts perfect... most the time i have to sit in the pits for 30-60 mins fans on high and hood up and just idle...

sucks but the 3-4 works when i dont turn the car off...

learned all i have to do it go part throttle in the parking lot and pull into the lanes (as long as the car sees a 3-4 shift)

my problem is my car has as blower (tvs1900) and the IAT would go through the roof if I let it idle.

[thesubfloor]

but my LS7-powered 2007 A6 Corvette shifts perfectly every time, all the time no matter whether it's been sitting for several hours or if I hot lap the car 3 or 4 times in a row.

Now having said that it might be relevant to note I'm currently on my 8th 6L80 (with this most recent one being a rebuild from Century Transmission in TX using the new Alto clutches) so it definitely wasn't an easy journey getting to this point. I was able to blow up #5 (a dealership rebuild) and #6 (a low mileage one from a 2008) in 23 passes each at the track and was ready to do a 4L65 conversion before I eventually got in touch with Century.

Although I was hoping to have Mike put me in touch with someone who raced their car as much as I do (I already have just over 190 passes in 2010 alone) and could attest to the longevity of the Alto clutches, no such person existed so I basically ended up becoming his "test mule" which I was more than happy to do.

The first one he built (#7) lasted 83 low 10 second passes before it let go as a result of a lip seal that rolled off causing the 3-4-5 clutch pack to burn up prematurely. When he tore it down last week, had he not been able to find a proverbial smoking gun as to the cause of the failure I might have been concerned but was relieved that it was a different part that let go and not the clutches.

With trans #8, as of last Wednesday night I have made 53 perfect passes out of 54. The one and only time it didn't shift properly was on the very first pass when it bounced off the rev-limiter on the 1-2 shift which didn't really surprise me as I've had this happen on several of the other transmissions after running them at the track for the first time.

Given the clutch packs controlling the 3-4 shift are the smallest (and weakest) in the 6L80, I think the reason that my A6 behaves so well is a combination of the Alto upgrades as well as the tuning changes. For anybody interested in trying out my transmission settings I've posted up my current tune.

[bluegoat06]

Wow, i didn't know the 3-4 clutch packs were the weakest ones. I guess that's why you have 0% TM for the 1-2 and 2-3 shift, but 100% for the 3-4. i'll add more TM in my 3-4 shift, i run 10% now, even though i don't have LS7 power levels, but i really like to have a long lasting trans. Thanks for info

[bluegoat06]

everytime i hot lap mine it shifts perfect... most the time i have to sit in the pits for 30-60 mins fans on high and hood up and just idle...

sucks but the 3-4 works when i dont turn the car off...

learned all i have to do it go part throttle in the parking lot and pull into the lanes (as long as the car sees a 3-4 shift)

I'll try the parking lot idea letting her do the 3-4 shift. Thanks for the info.

[thesubfloor]

Wow, i didn't know the 3-4 clutch packs were the weakest ones. I guess that's why you have 0% TM for the 1-2 and 2-3 shift, but 100% for the 3-4. i'll add more TM in my 3-4 shift, i run 10% now, even though i don't have LS7 power levels, but i really like to have a long lasting trans. Thanks for info

I have all my TM turned off.

Although I've got a mix of 1's and 0's under Shift Torque Factor, none of that comes into play as I've disabled my Upshift TM. The only reason those values are like that was from when I was playing around with it and just never set the values back.

[thesubfloor]

Wow, i didn't know the 3-4 clutch packs were the weakest ones. I guess that's why you have 0% TM for the 1-2 and 2-3 shift, but 100% for the 3-4. i'll add more TM in my 3-4 shift, i run 10% now, even though i don't have LS7 power levels, but i really like to have a long lasting trans. Thanks for info

The other thing is that according to my trans builder TM is designed more for smooth shifting than overall longevity. As is the case with the 4L60 it's best to have the shifts happen hard and fast to minimize clutch slippage.

[8850]

The other thing is that according to my trans builder TM is designed more for smooth shifting than overall longevity. As is the case with the 4L60 it's best to have the shifts happen hard and fast to minimize clutch slippage.

Thanks for posting your file. Good info in there.

I understand how a hard and fast shift would minimize clutch slippage but in my logs with TM enabled not sure the result is less clutch slippage. My timing advance is reduced to negative values at shift resulting in a smoothing effect. I also have my shift times shortened somewhat. I doubt this will create more wear on the clutches. Don't know for sure but maybe there is slippage as well with TM enabled. Ideally, my preference would have advance reduced with almost negative clutch slippage.

[thesubfloor]

Thanks for posting your file. Good info in there.

I understand how a hard and fast shift would minimize clutch slippage but in my logs with TM enabled not sure the result is less clutch slippage. My timing advance is reduced to negative values at shift resulting in a smoothing effect. I also have my shift times shortened somewhat. I doubt this will create more wear on the clutches. Don't know for sure but maybe there is slippage as well with TM enabled. Ideally, my preference would have advance reduced with almost negative clutch slippage.

I based that info on what Mike told me after he tore it down - despite the 83 low 10 second passes and with TM completely turned off the rest of the transmission looked brand new. Given that I was able to kill two stock transmissions in 23 passes each, we both figured that if TM actually hurt the transmission it definitely would have shown up but it ended up being in great shape.

Also, not to scare anybody even more but with the four that let go prior to the two Mike built for me, in every single case I knew they were starting to die when the car stopped shifting into 4th at the track.

The other thing I noticed while reading this thread is that people seem to be bumping up their line pressures by using the table in the beta that can apparently kill the 6L80 by actually storing lower values in the TCM. I personally stopped using the beta for my car a few months ago for that very reason and won't touch it again until this bug finally gets fixed.

[8850]

I based that info on what Mike told me after he tore it down - despite the 83 low 10 second passes and with TM completely turned off the rest of the transmission looked brand new. Given that I was able to kill two stock transmissions in 23 passes each, we both figured that if TM actually hurt the transmission it definitely would have shown up but it ended up being in great shape.

Also, not to scare anybody even more but with the four that let go prior to the two Mike built for me, in every single case I knew they were starting to die when the car stopped shifting into 4th at the track.

The other thing I noticed while reading this thread is that people seem to be bumping up their line pressures by using the table in the beta that can apparently kill the 6L80 by actually storing lower values in the TCM. I personally stopped using the beta for my car a few months ago for that very reason and won't touch it again until this bug finally gets fixed.

Hadn't heard that about the beta. Good to know even if my engine makes way less power than yours.

[G8-4-speed]

Hadn't heard that about the beta. Good to know even if my engine makes way less power than yours.

It is only the "max pressure vs gear" table. If you change the pressure and upload the tune with "another" tuner it will show "0". If you don't change the table, it is fine.

[BlkLS3]

Hoping you have had some luck.

I'm still fighting the same problem. I went back to the track this weekend after using most of the settings in the tune Subfloor graciously posted. I only made two passes. First pass still did not shift to 4th so I tapped the paddle but it went to 5th. Second pass I attempted to drive th car in the pits and let it shift into 4th before running, but they kept me in the lanes so long I ended up shutting down anyway. Went home before I broke something. I'm not sure I have not damaged the 3 to 4 clutches already anyway. Annoying thing is I have made 3 runs on the highway at full throttle and it shifted to 4th every time.

At this point I'm saving up for a transmission...