# A6 tranny "lunge" at stoplight?



## 70AARCUDA (Nov 14, 2010)

...ok, how many people (A) experience a "lunge" when driving away at a stoplight? And, (B) how severe would you describe that "lunge"?


----------



## RS LTZ (Jan 5, 2011)

Like you said in the other thread, a 'Forward' movement was a better choice than 'lunge' but they both work.

It's more noticeable when it's just me in the car as opposed to me + passengers


----------



## shawn672 (Oct 31, 2010)

If you lunge, you're pressing too hard on the gas pedal. I know what you're talking about. The tranny does some funky "hunting" thing where it tries to upshift/downshift at the same time, i cant explain it


----------



## 2011lt1 (Dec 13, 2010)

shawn672 said:


> If you lunge, you're pressing too hard on the gas pedal. I know what you're talking about. The tranny does some funky "hunting" thing where it tries to upshift/downshift at the same time, i cant explain it




i know what he's talking about. at a light and you let off the brake and it just takes off without any throttle. check you vin in the service bulletin thread for the transmission. that's exactly how mine acted prior to the new tcm program. in fact the difference was so dramitic after the new program it doesn't move at all. now when i let off the brake. night and day difference. mine use to take off after making like a 90 degree turn and as soon as i stepped on the throttle it would be like mazda's zoom zoom, after the flash that was gone too


----------



## RS LTZ (Jan 5, 2011)

Well when mine does it, it's right after I let off the brake and before I hit the gas pedal, so I'm giving it any input. 

Also, all the TSB's were applied to my car at the factory


----------



## SilverCruzer (Nov 30, 2010)

I am not sure I understand what the lunge is. Are you saying the car moves forward before you hit the gas but just after you let your foot off the brake? If so, I would say I don't.


----------



## RS LTZ (Jan 5, 2011)

It's more of a forward movement or a bump. It's hard to explain, but its not like the car accelerates forward or anything. But right after I let off the brake (before hitting the gas), I feel some kind of bump like it's shifting back into gear.


----------



## Knightslugger (Jan 11, 2011)

a *bump*?

bumps were a common occurrence on the 4l60e transmissions on the trailblazers, where a person would experience a sensation as if they were tapped from behind. turns out it was the transmission going from 2nd gear to 1st gear while stopped or just after rolling forward, which would feel like a sudden lunge.


----------



## SilverCruzer (Nov 30, 2010)

OK. No, I don't experience it, but I am pretty sure its the whole put-in-neutral-while-stopped-automatically thing not working correctly.


----------



## shawn672 (Oct 31, 2010)

Knightslugger said:


> a *bump*?
> 
> bumps were a common occurrence on the 4l60e transmissions on the trailblazers, where a person would experience a sensation as if they were tapped from behind. turns out it was the transmission going from 2nd gear to 1st gear while stopped or just after rolling forward, which would feel like a sudden lunge.


I believe this is what's happening. The car is in neutral at a stop light, and then you let off the brake and it shifts into 2nd, and then into first. Before the reflash the transmission does some wild hunting of gears from what I saw


----------



## RS LTZ (Jan 5, 2011)

The next time I'm out by our dealership I'm going to stop in and see if they say its normal or not.


----------



## booradley (Dec 20, 2010)

I have posted about his before, and the bump and lunge both apply. Besides the slight surge, when this trans is cold it is brutal. As I said you should be wearing the Nascar Collar Device. Once it is up to temp it is better. This trans seems never to be sure what gear it should be in? Not the smoothest transmission on the market. My dealer told me to wait 500 miles so the car can get used to my driving patterns. Humm? Had the re flash and somewhat better. It does drift backward on hills more than some of my other cars.


----------



## GM_6T40_Trans_Engineer (Feb 26, 2011)

RS LTZ said:


> It's more of a forward movement or a bump. It's hard to explain, but its not like the car accelerates forward or anything. But right after I let off the brake (before hitting the gas), I feel some kind of bump like it's shifting back into gear.


The 6T30/40/45/50 transmissions are clutch to clutch. At anyone time, 2 clutches are applied to provide a gear state. When a shift occurs, one clutch is left applied while the second is released. While the second clutch is releasing, a third clutch is being applied. 

With zero wheel speed, no throttle input and brake applied, one clutch is released to provide a "neutral" state. This in turn reduces load on the engine, providing better fuel efficiency. The bump, you may feel, is the second clutch being reapplied when you release the brake.


----------



## Uns69 (Jan 30, 2011)

Since my 2/4 reflash, I have much less of a trans bump/lunge when I release the brake


----------



## montgom626 (Jan 16, 2011)

*No problems*

Mine has no bump or lunge.


----------



## TSURacing (Jan 1, 2011)

I have found that I CAN induce the bump if I ease off the brake really slowly. If i just lift off the brake without applying any throttle it does the creep fairly smoothly. If I am applying throttle in short order as is usual for leaving a stop light I do not experience the issue. So the issue is not a ghost, but it is not much of a concern with my particular driving style.


----------



## fastdriver (Jan 7, 2011)

Just picked mine up on Valentine's Day. NO lunge/bump. Just about 500 miles on it today! 

FIRST tank of gas last week, highway/city, was 24.8 MPG going 310.8 miles. Car took 12.5 gallons. The car computer and my computer BOTH had the EXACT same figures!


----------



## montgom626 (Jan 16, 2011)

fastdriver said:


> Just picked mine up on Valentine's Day. NO lunge/bump. Just about 500 miles on it today!


I start out in second gear now with the auto in manual mode. Keeps the revs down and I see no difference other than maybe better mileage.


----------



## jeremylanders (Feb 10, 2011)

Can someone help me find out the problem I am having. See when I am driving around in neighborhood streets I can get it up to about 30-35 then lay off the gas...and do not hit the break. When the speed gets to about 25-20 I feel this lunch and notice the RPMS spike about 500 RPMS. If I press the brake down, there is still a spike in RPMS but it's not as severe.

Is anyone else noticing this or can it be fixed by something. I didnt notice it the first couple of days I had the vehicle. But it is there now and I can recreate it at will.


----------



## RS LTZ (Jan 5, 2011)

jeremylanders said:


> Can someone help me find out the problem I am having. See when I am driving around in neighborhood streets I can get it up to about 30-35 then lay off the gas...and do not hit the break. When the speed gets to about 25-20 I feel this lunch and notice the RPMS spike about 500 RPMS. If I press the brake down, there is still a spike in RPMS but it's not as severe.
> 
> Is anyone else noticing this or can it be fixed by something. I didnt notice it the first couple of days I had the vehicle. But it is there now and I can recreate it at will.



You're probably just noticing the downshifting, my Cruze does the same thing.


----------



## jeremylanders (Feb 10, 2011)

RS LTZ said:


> You're probably just noticing the downshifting, my Cruze does the same thing.


Well this doesn't seem normal to me. I mean are the RPMS suppose to spike UP when downshifting? It also happens while rounding corners. And I am very aware of it in stop and go traffic...it's almost dangerous.


----------



## Uns69 (Jan 30, 2011)

jeremylanders said:


> Well this doesn't seem normal to me. I mean are the RPMS suppose to spike UP when downshifting? It also happens while rounding corners. And I am very aware of it in stop and go traffic...it's almost dangerous.


 
I would bring it in an let them do the latest reflash. My downshifting improved 90% since my reflash. However, when its cold my cruze still shifts like crap before it gets to proper temp.


----------



## jeremylanders (Feb 10, 2011)

Uns69 said:


> I would bring it in an let them do the latest reflash. My downshifting improved 90% since my reflash. However, when its cold my cruze still shifts like crap before it gets to proper temp.


Okay I will try that and see if it works. I have read some of the reports and it seems after a certain VIN all cars should be fine...and mine falls after that number...But I'll check it out.


----------



## shawn672 (Oct 31, 2010)

jeremylanders said:


> Well this doesn't seem normal to me. I mean are the RPMS suppose to spike UP when downshifting? It also happens while rounding corners. And I am very aware of it in stop and go traffic...it's almost dangerous.


RPM's shift up when you downshift, yes.
I either think there is more to this story, or what you are experiencing is completely normal.


----------



## jeremylanders (Feb 10, 2011)

shawn672 said:


> RPM's shift up when you downshift, yes.
> I either think there is more to this story, or what you are experiencing is completely normal.


Are you suppose to feel the car jerk forward?


----------



## RS LTZ (Jan 5, 2011)

jeremylanders said:


> Are you suppose to feel the car jerk forward?


The tranny in these cars isn't as smooth as it should be, because of that, it's obvious (at least in my car) when the car downshifts. 

In either situation higher RPM's (under coasting or braking) would help slow down the car so it's not really a safety issue.


----------



## TSURacing (Jan 1, 2011)

On my car the downshift smoothed out around 1500 miles. It is still noticeable, but it is not intrusive at all. After 15 years of commuting in a MT car, it is fairly natural to me anyway.


----------



## shawn672 (Oct 31, 2010)

jeremylanders said:


> Are you suppose to feel the car jerk forward?


Yes you may, thats part of the second clutch grabbing, like the engineer posted earlier

At around 3k all of my problems went away. I'm currently at 5500miles and it's as smooth as butter


----------



## GM_6T40_Trans_Engineer (Feb 26, 2011)

jeremylanders said:


> Are you suppose to feel the car jerk forward?


How many miles do you have on your car?


----------



## former farmer (Jan 10, 2011)

*Down shifting*



shawn672 said:


> At around 3k all of my problems went away. I'm currently at 5500miles and it's as smooth as butter


Shawn, 

Do you still notice the downshifting happening? I have almost 2,500 miles so far and can still notice the downshifting quite a bit.


----------



## RS LTZ (Jan 5, 2011)

I have about 1,500 miles and it's nearly what it was when I drove it off the lot with 47 miles


----------



## shawn672 (Oct 31, 2010)

former farmer said:


> Shawn,
> 
> Do you still notice the downshifting happening? I have almost 2,500 miles so far and can still notice the downshifting quite a bit.


nope, currently at 5500 miles i think the tripodometer said, and i have 0 issues. its butter smooth up and downshifting

around 3k all of my "problems" went away, i experienced some of what everyone here has said. if you still have issues after 3k i would take it to the dealer and have them test drive it. what you're experiencing could be normal


----------

