One of the annoying things I find about the way the A6 transmission is programmed is the 3>2 downshift.

Lets say you're trying to pass a car at about 50-60mph. You push on the gas to go around. The car doesn't respond as quickly as you need it to, so you keep pushing on the pedal. As you pass about about 80% throttle on the TPS sensor and 63 mph the car now downshifts all the way to second gear. The result is instant tire spin and engagement of the traction control, which pretty much shuts the car down while you are in mid pass. To say the least, this is more than just a little dangerous. It can get you killed if you aren't careful.

I'm starting to think that the problem is that GM programmed the car to downshift one gear too far, and that the speeds at which the programing on the transmission for 3>2 downshifts is too high. If you take the throttle all the way to the floor (100% on the TPS) the car will downshift to 2nd gear all the way to around 85mph. A second gear downshift at 85mph is asking for trouble. Not to mention how hard it is on the transmission.

GM needs to rethink the programming on the transmission. The car should deliver a linear and predictable power increase from the transmission and engine and it should progressively downshift one gear at a time as you push on the pedal. The instant 4 gear downshift that can occur when you go from cruising at 55mph in 6th gear to 2nd gear results in too drastic of a power increase. I believe they should drastically lower the max speeds at which the car will downshift to 2nd gear to around 40mph. The way the A6 is programmed now, it pretty much makes it impossible to safely take the gas pedal to the floor at any speed over about 30mph.

I'd like to hear others thoughts on this. Have you ever been surprised by the 4 gear downshift at speed when you go to pass another vehicle?

 

Never.

 

What year model car is yours? I ask because GM made some changes to the A6 transmission in 2010. Maybe they fixed this??

 

chuck COW Tune will take care of that.

 

I know the Corvette automatic transmission doesn’t afford the precision and control of the manual shift and suffers shift-lag in certain circumstances but if the transmission downshifts into 2nd gear at 85 mph that’s almost unbelievable. Wouldn’t drag control engage? I don't know but are you sure 2nd gear is being engaged when you downshift at 85 mph?

I couldn’t imagine being in 6th gear going only 55 mph either but that’s a different story.

 

I have never experienced what you have described. I drive alot of 2 lane highways loaded with "Stevie Wonder Tourists" and pass ALOT. I enjoy going by them in a blink of an eye....and never had the traction control activate. I have a 08 A6

 

Oops. Looks like I'm reading KPH, not MPH. Let me back up and regroup.

 

Ok, max speed on the 3>2 is 50mph. Which I still think is a bit too high.

 

With a manual transmission, you can select the gear you want, and use the gas pedal to modulate the amount of power you want from the car, and you can even take the pedal all the way to the floor if you need to.

With the A6, the gas pedal controls gear selection in addition to engine output, and if the speeds at which the car shifts in relation to the throttle position are not done correctly, you can end up having the car shift down one gear too far in some cases. Part of the problem may be addressed by programming the car so it downshifts sooner so you don't have to press so far into the throttle to make it downshift, but I also believe the upper speed limit for the 4 gear downshift to 2nd gear needs to be lowered. Maybe I'm wrong on this, but that's my current thinking.

 

Fred,
Thanks fior the feedback. I'm going to document this. Please don't hesitate to contact us with questions, comments or concerns.

Chevrolet Customer Service,
Justin

 

This did happen to me about two weeks ago. I wanted to pass a truck doing about 58. I was looking for a downshift from 6th to 4th - maybe third. Put the hammer down about 1/2 way to floor (I have actually practiced this.) Next thing I know car is screaming and won't upshift. I look down and HUD says 2nd gear and I'm bouncing off the rev limiter. I HAD NOT (intentionally) engaged/been using the paddles. It took me 2-3 seconds to process this then I started mashing the paddle to upshift. It was dangerous and a bit embarrasing. I tried to duplicate this 3-4 times on the way home but everything was normal. Scared me. 2011 GS ~2300 miles.:o

 

Thanks. It seems like most of the problems I see with the A6 are when it does a 4 gear downshift. The car has so much torque, I think in nearly all cases, downshifting to 3rd gear is all it needs to do. I'd just like to see it not drop into 2nd unless you were really going slowly, cause I think it is overkill, and all it does is result in wheelspin anyway. Its also got to be hard on the whole drivetrain when it does this.

It also would be helpful if you didn't have to floor the pedal to get it to downshift in the first place. It needs to make progressive downshifts without having to push the pedal so far down. This just exacerbates the issue, since by the time it does decide to shift, you nearly have your foot to the floor.

 

 

 

That will happen in my CTS as well. Have to be careful. One of the reasons that I spend a lot of time in the CTS manual mode.

 

ECS Tune will help as well.. or, use the paddles to DS to 3rd and mash it and pass, and then back to D.

 

This car had a CoW tune in it, and now an ECS tune. If you would like a file that does not let it downshift to second at 50mph I can do that Fred.
That sounds like more of a tire problem then a trans problem to me though.

 

If it has a trans tune why does the OP say GM Tune? Even the GM Customer Service posted?

Quote the OP...I'm starting to think that the problem is that GM programmed the car to downshift one gear too far, and that the speeds at which the programing on the transmission for 3>2 downshifts is too high

 

you are right on with this, I agree 100 percent.

 

Ironically, I was following my wife home yesterday. I was in the Vette, on a 4 lane going downhill in a right then left "S" curve at about 65 MPH. She is in the left lane because we had about 1/2 mile until we turn left off the 4 lane. So, I figured I would blow by her and let her hear "Scarlette" (my daughters like to name cars) scream. I rolled into it and the RPM's went from 1100 to somewhere in the mid 5000's instantly. Scared the bejesus out of me. Luckily, I have a chicken bone the size of an elephant femur which caused me to breath the throttle long enough for may brain to realize that no-one's life was in any immediate danger. So I rolled the throttle down again, a little slower this time, and smoked Mama's Highlander back to da house. I agree, one less downshift would have been less terrifying.