smaynor

Sorry for this being so long, but I want to fully describe the issue I'm having with my 2006 A6.

The car:
2006 Base w/A6
Vortech Supercharger
ARH Headers
Yank PAS3400 Stall
Vengeance Tune
551 RWHP 506 RWTQ
275-40-17 MT Drag Radials

I drag race my car almost every weekend. The issue I am having is the car will not shift under WOT. I'm hitting the rev limiter on both the 1-2 and 2-3 shift on every pass, unless I let off the pedal a bit to let it shift.

This problem really became an issue once I installed the blower. I've yet to make a clean WOT pass this year.

I have adjusted my shift points down to 4700 RPM, and it still hits the limiter, unless I run part-throttle (which is no fun!)

I do not have HP tuners. The only thing I have is a Diablosport Intune that I use to adjust the shift RPM. I have read on here, however, that under WOT, the trans goes by MPH, not RPM. By running the slightly smaller rear tire, could this be throwing my shift points off that bad?

BTW, when I installed the new converter a couple weeks ago, I took the opportunity to drop the trans pan and change the fluid, filter, etc. The pan was absolutely spotless. The tiniest bit of sludge on the pan magnet, fluid clean and no burnt smell, filter clean as a whistle.

Can anyone offer any suggestions on what I could try next? It was so bad this past weekend, I killed the alternator by hitting the limiter so much (and I was working to stay off it). Had to replace it Saturday.

But, at least I did come home with a win in the class I entered.

Thanks!

realcanuk

The 6L80 transmission shifts are triggered by MPH. The tune needs to be adjusted for tire height, which in turn corrects the speedometer. After that the mph needs to be adjusted along with rpm.
There are other issues as the transmission works off a torque output model which is now different from stock because of your blower. There are tables to adjust to bring this into line, as well as pressures and shift times.
On top of all of that, a converter change requires tuning also. There is no way that thing is going to shift properly with all the changes you have made to the car.
You need to seek out a tuner who knows what they are doing. 6L80s are tricky and if not tuned right they don't last long especially when racing them.
You also should absolutely install a tranny cooler when running a stall converter, as the temps will increase dramatically. Heat is the enemy as far as transmissions go.

smaynor

I do have a trans cooler. Installed it when I did the converter. Temps are well within the normal range.

All the mods were in place, with the exception of the converter, when the car was tuned by Vengeance. They did a trans tune along with the engine tune.

Thanks

realcanuk

Got it. From the way your first post read I didn't realized it was tuned. Obviously they didn't get it dead on, which is very hard to do if not actually at the track. Just requires tweaks to the shift point to get it in line I guess.
If you lower the shift rpm, but not the mph, it wont help.

smaynor

THAT is what I've started to realize. I'm going to work on in tonight to see if there is a way I can change my MPH down a bit, but I'm not sure if the Intune will do that. I've only seen RPM in the TCM options.

I may just have to invest in HP tuners so that I can work on it as needed. I would gladly buy the tool, but I don't have a darn clue about trans tuning.

Thanks for your help!

realcanuk

If you get hpt, changing shift mph and rpm are very simple. Just leave everything else alone unless you understand the effects of the changes your make.
I use hpt myself and would happy to help if you have questions.

Fordracer9

1 more thing that hasn't been addressed. If the car sees ANY wheel spin, the A6 will NOT shift. You say you are on DRs. How old are they, and are you sure that they're not spinning at the top of the gear?

subfloor@centurytrans

I used to think this too but discovered it's not completely true.

When I ran Mickey Thompson drag radials and didn't hook right as the car launched, the run was basically over and I would usually just coast to the finish line.

With the Hoosiers that I now run however, they work phenomenally well at rehooking if I happen to spin off the line and I've even managed to win a few races that I otherwise would have given up on.

If you look at the scan shown below, I got a fair bit of wheelspin initially but the car still shifted fine for the rest of the pass after I regained traction.

Devilish34

Pretty much this.. It took me about 9 trips to the track to get it where we were happy.

Post a screen shot of where your wot mph and rpms are set..Also some tuners shorten the shift time to much thinking.

smaynor

The DR's were purchased in January of this year, and have exactly 32 passes on them. They are Mickey Thompson 275/40-17.

Sometimes I do get some spin at the top of 1st gear. When that happens, I just let off and coast it out. Not worth risking losing control and wrecking the car over trying to salvage a run. If I spin off the line, I will let off and try to roll back in. I'm working on controlling that wheel spin right now. Leaving off a 3400 stall v/s a stock converter is taking some getting used to!

smaynor

BTW, Thank you Subfloor for your advice. I was hoping you would drop by and give some input. You seem to be one of the most knowledgeable people here about the A6.

When my trans gives up (when, not if), I will be contacting Century for the rebuild and/or parts. Yours seems to be the most abused, longest lasting A6 on the forum!

Devilish34

Next go around try the Hoosier drag radials.. They IMO are the best DR out there.. They also recover better than the MTs if they spin

subfloor@centurytrans

No problem.

There's something else to consider and it elaborates a bit on something realcanuk mentioned earlier.

If you're running injectors larger than 63lbs but your transmission settings weren't scaled correctly then I can pretty much guarantee it's never gonna shift properly no matter what tires you have on it.

In 2009 and older cars the PCM has a 63lb injector limitation and running larger ones than that can mess up your transmission quite a bit. Basically what happens is that in order to get the injectors to work at all, the MAF values needs to be scaled to effectively fool the PCM. While that works fine for the engine, it does however cause the amount of calculated torque to be misreported which is what causes the transmission shifting issues. What you end up with is the engine making 600 lb/ft of torque (as an example) but the PCM thinks you're only making 300 lb/ft so it sets the line pressure in the transmission to the smaller calculated value and voila, it won't shift properly.

smaynor

They are 60# injectors.

Again, everything was in place, with the exception of the stall, when Vengeance did the tune. He did do a trans tune while on the dyno, but I'm not sure what he did as far as trans settings. I expect that my car wasn't the first A6 he had seen, but I don't know anything about tuning a trans anyway.

realcanuk

I don't know when the original tune was done but there were tables added not to long ago to HPT to actually adjust the torque model and get the reported torque closer as opposed to previously where other adjustments had to be made to get these things to shift.

smaynor

Tune was done on January 11, 2014.

It was right after I finished installing the blower. Tune was done, however, with street tires, which are slightly larger diameter than my drag radials.

I did look through some things on my Intune yesterday. I did find a place where I could set the tire size. I changed that to the correct size, and also adjusted the shift points again. Drove it around a bit tonight and then ran down to Mexico and made a couple WOT starts.

It actually shifted! Now, I'm not going to get overly excited just yet. We will see what it does at the track Friday night, but at least it did shift at WOT, even with a good bit of spin on one start.

realcanuk

Good news! If the tire size is off, the speedo will be and therefore the shift points. Tire spin won't prevent a shift unless it is actually trying to shift while the tires are spinning.

CI GS

This is an interesting thread. I've always heard that it's the MPH that determines the shift points and have seen as well that the WOT Shift Speed needs to be adjusted to change the shift points.
But, what I don't get is the math that GM uses to determine the shift speeds.
What I mean is: I have looked through the TCM tables on all of the TCM tunes that I have on my laptop for my Vette, my Sierra Denali and my brother's 2010 Camaro, and the indicated WOT Shift Speed for each of them is around 10 MPH below what I calculate the shift speed should be at the desired shift RPM. For example, I calculated that at the designated shift point of 6400 RPM, with a 2.73 final drive, a 4.03 first gear and a 26.12" tire, my car should be doing 45.29mph in First gear. But, the shift speed given for the WOT shift speed for 1-2 in the tune is 32.9 mph??? Ditto for the shift speeds for all the other gears as well. WTH?
I see the same kinda thing with all of the other TCM tunes that I looked at.
So, what's up with that? If the shift speed is what determines when the transmission should shift, why is the indicated WOT shift speed so much lower than what the car is actually travelling when it shifts??
Or am I missing something here?

REDC4CORVETTE

The trans tune is wrong!!
The tables for the trans need to make the trans keep the line pressure up in anticipation of the next shift or the car will redline in every gear.
If the trans is tuned right the engine rpm's should raise when the trans down shifts ,if it doesn't then the trans needs the computer reflashed so it maintains a load on the engine.You should see engine drag engauged when slowing down at times, if the trans is set up right .You will burn up the trans if you keep it the way it is.
Call Chuck Cow he knows about this problem.

realcanuk

What you are missing is that the mph commands the shift. In my logs the shift is commanded at the mph I set every time. Now, when the shift completes is another story. It takes a certain time to complete (based on many settings and variables) and in a car with big power, especially in lower gears it can be quite a few mph until it does. The trigger speed needs to be below where you want the actual shift. How much is trial and error as it varies.