Automatic transmission
#21
4th Gear
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2014 vette: automatic transmission
car was in the shop for 2 weeks, 400 miles driven by 2 employees there and could feel what I feel while cruising. GM says everything is as it should be so I guess I have the most expensive 4 cylinder car ever built that I am stuck with. I did put the selector to sport mode instead of touring and will have to paddle shift to get up over hills. Really disappointed with their R&D.
#22
Le Mans Master
car was in the shop for 2 weeks, 400 miles driven by 2 employees there and could feel what I feel while cruising. GM says everything is as it should be so I guess I have the most expensive 4 cylinder car ever built that I am stuck with. I did put the selector to sport mode instead of touring and will have to paddle shift to get up over hills. Really disappointed with their R&D.
#23
Burning Brakes
A large percentage of the time mine shifts back to V8 quickly when load is applied. But sometimes hangs in V4 with loss of throttle response, garbled exhaust sound then vibration and finally back to V8 and all is well. I too am disappointed that corrective action by GM has been absent on this issue. I know it can be tuned out, but am not confident enough to void powertrain warranty on this new LT1 yet! This is a problem GM should correct with out turning buyers sour towards them. Is a smooth running V8 a thing of the past. Hot Rod Mag Dec Issue talks about boost in V4 mode on Z06, interesting they would allow such programming.
Last edited by Jim Barker; 10-13-2014 at 11:22 AM.
#25
Pro
#26
Burning Brakes
Service Bulletin
GM Bulletin No.:
Date:
14628
September 2014
SERVICE UPDATE
SUBJECT: Service Update for Inventory Vehicles Only
Drive Audit for Transmission Noise and Loss of Reverse
Vehicle Limited to 3rd and 4th Forward Gear
Expires October 31, 2015
MODELS: 2015 Chevrolet Corvette
Equipped with 8 Speed Automatic Transmission (M5U)
This service update involves vehicles in dealer inventory only and will expire October 31, 2015.
This bulletin provides a service procedure to perform a drive audit on all 2015 model year Corvette vehicles in inventory that are equipped with an 8 speed automatic transmission (M5U). A small number of transmissions may develop a crack in the triple clutch housing internal to the transmission, leading to noise, loss of reverse gear, and limiting the driver to 3rd and 4th forward gears. The drive audit must be completed before vehicle delivery (and in addition to normal pre-delivery inspection activities) to identify vehicles with the condition. If the condition is found, dealers are to replace the transmission under the existing exchange program, see PIP5200A for details.
GM Bulletin No.:
Date:
14628
September 2014
SERVICE UPDATE
SUBJECT: Service Update for Inventory Vehicles Only
Drive Audit for Transmission Noise and Loss of Reverse
Vehicle Limited to 3rd and 4th Forward Gear
Expires October 31, 2015
MODELS: 2015 Chevrolet Corvette
Equipped with 8 Speed Automatic Transmission (M5U)
This service update involves vehicles in dealer inventory only and will expire October 31, 2015.
This bulletin provides a service procedure to perform a drive audit on all 2015 model year Corvette vehicles in inventory that are equipped with an 8 speed automatic transmission (M5U). A small number of transmissions may develop a crack in the triple clutch housing internal to the transmission, leading to noise, loss of reverse gear, and limiting the driver to 3rd and 4th forward gears. The drive audit must be completed before vehicle delivery (and in addition to normal pre-delivery inspection activities) to identify vehicles with the condition. If the condition is found, dealers are to replace the transmission under the existing exchange program, see PIP5200A for details.
#27
I notice this all the time in my 2014 A6 as well. Seems if you are cruising and then all of a sudden hit the accelerator to get moving or pass somebody, it has a hesitation to it before it kicks in. kind of makes you lurch forward for a quick second before you get moving. I hate it but figured it is what it is. I would never tune it myself to get around this, but believe that Sport Mode and Track should be V8 and nothing else. Touring and below should be V4/V8 capable, not Sport or Track. Makes no sense. Do you think GM will do anything about this?
#28
Le Mans Master
I have a similar problem but I do not think it is the transmission. On full throttle acceleration from a 40 MPH roll the car would hesitate in touring mode. I decided to try sport mode and for a while it was fine.
The problem came back, it would hesitate and now backfire before it accelerated regardless of being in sport mode. Brought it to the dealer and they could not duplicate the problem
Since then I have noticed that I can not change the sound management (NPP) off. On several occassions I have also noticed that if I accelerate hard in sport mode but slow down before the anticipated next gear I can not choose the driving mode. It will go from track to weather and I can not pick anything in between. Once I stop and turn the car off the driving modes are fine.
I am really frustrated as these things happen ocassionally (with the exception of changing the sound management). For now the car sits in the garage until I have some time to actually record what is going on as the answer "could not duplicate the problem" is no answer and just a waste of my time.
I called GM customer service and they stated that no one has reported a similar problem and yet there is this thread. Looks like the old GM
The problem came back, it would hesitate and now backfire before it accelerated regardless of being in sport mode. Brought it to the dealer and they could not duplicate the problem
Since then I have noticed that I can not change the sound management (NPP) off. On several occassions I have also noticed that if I accelerate hard in sport mode but slow down before the anticipated next gear I can not choose the driving mode. It will go from track to weather and I can not pick anything in between. Once I stop and turn the car off the driving modes are fine.
I am really frustrated as these things happen ocassionally (with the exception of changing the sound management). For now the car sits in the garage until I have some time to actually record what is going on as the answer "could not duplicate the problem" is no answer and just a waste of my time.
I called GM customer service and they stated that no one has reported a similar problem and yet there is this thread. Looks like the old GM
#29
Mine does the same, but not as bad as described in the OP's post.
When just at a steady drive and I give it a little more gas, I can feel it more in the pedal than anything else. Just a slight shutter like it's switching back to V8 and trying to go down to 5th gear or something. I just don't get the "slowing" down feel like he stated.
I agree V4 should not be working in Sport or Track mode. I bought a sports car and I like to drive it as one. Long trips sure the V4 mode is good and it's great for future engine advancement.
When just at a steady drive and I give it a little more gas, I can feel it more in the pedal than anything else. Just a slight shutter like it's switching back to V8 and trying to go down to 5th gear or something. I just don't get the "slowing" down feel like he stated.
I agree V4 should not be working in Sport or Track mode. I bought a sports car and I like to drive it as one. Long trips sure the V4 mode is good and it's great for future engine advancement.
#30
Cruising
Member Since: Sep 2014
Location: Port Coquitlam BC
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Eco Mode
This sounds to me like a serious oversight by GM engineering. Its a performance car isn't it ? Why would they not at least give auto (A6 / A8) owners the option to use Eco mode.
I have an M7 so Eco Mode only if I choose to select it. On a recent trip I gauged the difference in fuel economy between Touring and Eco Mode and found that the difference was somewhere between 1 and 2 miles per gallon. What was very evident is the feel of the car in Eco Mode, engine does not sound right, shakes / vibrates, just sounds un healthy and I cant imagine what it will do to the engine long term. For me I will never put the car in Eco Mode again. I didn't buy it to save $5.00 on a tank of gas, if I wanted that I would have bought a cruze.
The M7 is a great transmission with the LTI, now if GM would just get rid of the stupid 1st to 4th gear mandatory shift. Who makes these decisions on sports car ?
I have an M7 so Eco Mode only if I choose to select it. On a recent trip I gauged the difference in fuel economy between Touring and Eco Mode and found that the difference was somewhere between 1 and 2 miles per gallon. What was very evident is the feel of the car in Eco Mode, engine does not sound right, shakes / vibrates, just sounds un healthy and I cant imagine what it will do to the engine long term. For me I will never put the car in Eco Mode again. I didn't buy it to save $5.00 on a tank of gas, if I wanted that I would have bought a cruze.
The M7 is a great transmission with the LTI, now if GM would just get rid of the stupid 1st to 4th gear mandatory shift. Who makes these decisions on sports car ?
#31
Burning Brakes
#32
I have the same issue with my 2014 A6 when in drive. I can definitely feel the V8 activation when I accelerate...but I also feel a lugging/shuddering as well. When using the paddles, all is ok. I have just assumed it is in the programming of the transmission, and been patiently waiting for an update.
#33
Burning Brakes
I have the same issue with my 2014 A6 when in drive. I can definitely feel the V8 activation when I accelerate...but I also feel a lugging/shuddering as well. When using the paddles, all is ok. I have just assumed it is in the programming of the transmission, and been patiently waiting for an update.
#34
My A6 transitions from 4 to 8 and 8 to 4 seamlessly. I've looked down at the gauges and watched the V8/V4 light several times during the transition.
If your car is lurching or lugging/shuddering or you have a short loss of power then something is wrong with your system.
If your car is lurching or lugging/shuddering or you have a short loss of power then something is wrong with your system.
#35
I am hoping the Chevy Customer Service folks can jump in here and let us know their thoughts on this? Is it normal for it to kind of delay when you hit the gas from V4 to V8 or is it an issue that needs to be looked at. If i am driving and it is in V4 and i just casually open it up (very easy), you don't notice the lunge. You only notice it when you put the peddle to the metal and it kind of lunges. Really would like to know what is going on here.
#36
Safety Car
My experience as well..
#37
Safety Car
They won't. Customer service positions are low wage entry level positions. They aren't techs, and could get in big trouble expressing any opinions at all... (in case you haven't noticed this already)
#38
car was in the shop for 2 weeks, 400 miles driven by 2 employees there and could feel what I feel while cruising. GM says everything is as it should be so I guess I have the most expensive 4 cylinder car ever built that I am stuck with. I did put the selector to sport mode instead of touring and will have to paddle shift to get up over hills. Really disappointed with their R&D.
#39
Pro
Same here.
#40
4 c. and trying to give it gas , it will drink more gas trying to pick up speed than you will ever save with the 4. in 8th.