Greetings!

I previously started a thread like this in Tech but wanted to repost here in General Discussion and get more input. Sorry for the goofy thread title


The A6 transmission in my 09C6 w/Z51 (9000 miles) in light throttle acceleration conditions like in traffic seems like the torque converter is not locking just right.

Hard(or impossible) for me to clearly explain what it does but I will try.

It does it in D or Sport mode, while using the paddles.

For instance: after slowing for traffic and resuming slight acceleration to increase speed the car is in third gear(using paddles) the engine reaches approx 1500/1600 rpm and then falls to 1200 rpm. Its almost like the transmission is changing gears...it does the same thing in any of the higher gears depending on the speed the car is traveling.

If this is normal thats great I will try and get used to it.
My question is (finally) Reckon GM has a "update" available for the A6 that will cure this ? I will probably carry it to a dealer and let them check it out but figured I would try and see if this is normal and if not, if you guys new what the solution is.

Thanks in advance for any help or tips.

Bert

Roll Tide!

 

We have an identical car (2009 A6 Z51) and I have not been able to duplicate this condition.
Sometimes if the tranny was just finishing an upshift and I apply some power (which would cause it to downshift), there will be a momentary "dead spot" in the throttle as the transmission figures out it now needs to downshift, and then does it. But the engine does not rev, nor does the tranny seem to slip; it just won't put the power back in until the shift is finished. Just like it should.

But you are not the first to wonder or complain about this, so something is happening with at least some of the cars. Some people get a trans tune. I'm reluctant to do something that would probably affect my 5/100 powertrain warranty and GMPP, when I don't seem to have the problem.

"The investigation continues..."

 

I have not expericenced that with my 08 A6. Having said that...my A6 does do some strange things. I chalk it off to it thinking it knows more than I do about when to shift/downshift. I also am considering a "tranny tune" from "COW" but he is to far away for a day trip to and from. I will wait for one of his excursions into the hinterland closer to me.

 

Our 09 is the same as yours and no it does not do what yours does, sluggish shifts and delays on downshifts are the norm from the factory, I will have that cured soon with the Chuck tune

 

With these low revs that you running you will notice this phenom. The TQ is in play.

You are actually lugging the car and the TQ is turning off so to speak. This is part of the GM build with the A6.

Keep the revs up a little higher ,say around 2K - 2.5K and it will not do this.

 

Chuck's tunes are phenominal. You should look into buying his AutoCal so he can tune your car without you having to leave your driveway.

 

I have an 07, completely tuned, and it does the EXACT same thing.

We have tried everything to correct the issue in the tune and nothing has worked.

It did it with a stock torque converter and it does it with this aftermarket torque converter. It's VERY annoying, but mine does it in 2nd or 3rd gear around 35mph. It's very annoying to be in 2nd gear and start to push it to have the rpms just suddenly dip.

What you describe is 100% identical to my situation.

If you find a solution , please let me know. My tuner has been trying to fix it over 3 different occassions with various suggestions from other tuners and forum members with no luck.

 

Under the factory calibration the converter is not even able to lock until you are in 4th gear, prob why you only see it in higher gears.

 

Um...OP sees it in 3rd gear and I see it in 2nd and 3rd.

Doesn't help us, lol.

 

I noticed something similar to Floyd's comment.

I have an '07 (base) with the A6 (and no tune or anything aftermarket).

I notice that if I am going around 35mph (give or take up to 5) and am under light acceleration ... if I pull off the gas pedal (even just maybe 75%), it will drop the rpm's and feel almost like it is 'lugging' the engine. I say 'lugging' (even though I'm not a mechanic and may be using an incorrect term) and what I mean is that it feels like this: if you are using the paddle shifters and accelerate a lot, but don't shift, when you let go of the gas pedal it gives that odd feeling almost like it's losing power and slows down quickly.

I don't know if that's the same feeling y'all are having. I -only- experience it around the 35mph (give or take) mark and if it is under light acceleration (like in a parking lot or a residential zone where zone are 35mph).

 

I haven't tried accelerating hard past that point and then letting off the gas to experience it, but what I'm talking about is best described and experienced by giving the car light/moderate throttle DURING acceleration....say 50% throttle and when I hit around 35mph (like you said, sometimes a little lower or higher) the rpms drop and then continue to climb again.

It's like the converter is locking up there, but we have commanded no lockup except in the overdrive gears in my tune, yet it still does it consistantly.

 

I have the chuck trans tune. my car will do this as well, only in low rpms, I dont think the trans wants you to lugg in the high gear low rpm's, so it locks the converter?? It could be trying to keep the fluid from being tortured by the high load, low rpm situation. I found if you select a gear better suited for the situation it will not lock the converter. Never had it do it when i let the computer shift for me!

The COW trans tune is awesome! no more will your transmission quick shift into 6th at low speeds then get confused when you want to accelerate. Shifts like butter feeling every shift normal cruzing, hammer down it will get rubber into second rocket into third and so on. Fast positive shifts that wont break parts.

 

I have a 2009 A6 and don't experience any of the problems you described! I also read your post in the Tech section and tried to duplicate it myself and couldn't.

I underlined the sentence above to clarify if you are saying this happens while in paddle mode? If so, then I would be very concerned as the car should not be hurting for gears so you should be locked into a specific gear.

 

no problems here, have not even noticed any sluggish shifts. If you put the pedal down it goes and goes well either in drive, sport mode or sport mode using paddles. We came from an 09 mz6 with z 51 ratio gearing and we are really impressed with the 11 a6 and 273 rear end.

 

 

Yes, this is normal. What it is doing is locking the torque converter. The ECU will command the torque converter to lock in gears 2 through 6, after a few moments of relatively steady state driving in that gear.

If you are hard on the gas, it will delay locking the torque converter for longer, but it will still eventually lock.

 

Just get a chuck COW tune and you will be ok

 

I have a 2012 L1 with less than 300 miles and mine does the same thing.
I'm in the used car business and Ford converters are bad about that, best described as a bobble. There is a chemical in a tube, red in color, can't recall the name right now, that corrects this almost all at once. I wouldn't suggest putting this in a car that still is under warranty.

 

Thanks for the replies.
I would get a COW tune but I have a warranty for 5 more years

I was going to make an appointment at a dealership to get it checked for codes with a TechII and see if GM had any computer updates that might address this issue. But it sounds like its normal(in some cars)

Bert

Roll Tide!

 

The two months I had mine it only seemed to do that was in paddle mode and then it was when I was going too slow for that gear....It would not lock until IO achieved whatever speed that was...and there was always a slight hesitation...I usually ended up staying in paddle and in second to avoid that...

In D a light acceleration it would get to sixth in ridiculously slow speeds but I didn't notice the lock up phenomenon....