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automatic transmission is Boggy, sloppy & unsorted! Grrr.

7K views 43 replies 18 participants last post by  dblaron 
#1 ·
I know our G8 Gts are plagued with an automatic tranmission that bogs in a tall gear, hesitates, shifts reeeeeally soft, and at times "hunts" for the right gear. Mine seems to do all the above. I have never felt a tranny that seems to "fight" the car as much as the G8 automatic tranny does.

Mine is stock and unless I am in manual mode....the car is frustrating to drive aggressively.

In the regular and sport mode, it oftens bogs in a high gear and does not drop a gear in order to get moving when I hammer the gas.

Only exception is if I am driving either 20-24mph and hammer it or about 45mph and hammer it. Then it takes off and rips. But just about any other speed, it bogs in a tall gear.

Is that pretty typical??? I feel the need to get a cortex tune...(I have no custom tune shops where I live) do you think a cortex tune will help.

This transmission really annoys me. It just seems to fight the car.
 
#5 ·
Car will also bog if traction control is on. Torque management and traction control are very intrusive in the stock tune.
 
#6 ·
Slizzo, yep...I take traction control off. Still have the conditions above.
 
#7 ·
Yup, all in the tune then.
 
#8 ·
What state are you in? I have had the cortex tune and while it is a step above the stock tune I don't feel it is worth the money. Pat G can easily send you a tune 10 times better than a harsh shifting handheld tune.
 
#9 ·
Just talked with Pat G. I am confident his tune is superior for sure. Cost is double as well compared to a cortex...which I undertsand...because he puts a lot of his own time and expertise into reviewing the data logs and then adjusting.

I need to save $625 now for the Pat G tune!
 
#43 ·
I had mine done by Pat G and my buddy had his done by Reckart.

Pat G had the better trans tune for sure...even my buddy agreed.

It downshifts to the correct gear and with a lot less hesitation.
My pat g tune shifts soft under slight load, and smacks hard when in WOT.
My buddies reckart tune shifted hard all the time even under the lightest throttle
 
#11 ·
Dealer can due a relearn on the trans. Might flush out some stray electrons. Maybe the fluid level is low?
 
#12 ·
Because of ease of installation and cost, I went with the SC cortex tuner. I have only driven my car less than 10 miles because it decided to snow here. But I could immediately tell the difference in the transmission with the Rotofab 91 octane tune. I have heard it takes some driving time for the tune to really take ahold. Not sure if that is really true.

Anyway, I have been driving around my 1999 Ford Expedition which looks and drives like new (I seriously bought it from a little old lady who never drove it) So, I don't mind driving it, but I am really excited to get some miles on my G8GT to see how the tune takes ahold and performs.

I will report when I get some driving time.
 
#14 ·
We’re glad you like the G8, AllenK. Please, don’t hesitate to make an appointment with the dealership as GXPaycheck has suggested.

Michelle, GM Customer Service
Michelle and GXPaycheck,

I'm having the motor mounts replaced under warranty on my wife's G8 to see if it will cure the AFM lugging. I'm going to mention this problem to the dealership whenever I get the work done on the mounts for sure.
 
#15 ·
Our trans tune is sloppy from the factory, and the dealers can't do nothing to fix that unless you had a trans with bad seals, which would only address some an specific trans issue, the shifts would continue to be sloppy because the factory calibration seems to have been made thinking the G8 was a Camry :), such piece of work that even sloppy can tunes would make the trans feel better to drive.

Hopefully GM would do a better job in the new SS. They should learn a couple of things just watching our forum, as well as all other LSX powered car forums, where the 6l80e/6l90e is involved.
 
#16 ·
doubt they will use the 6l80 or 6l90.... ;)
 
#20 ·
Nice, can you spill the beans on the new trans model ? :driving:, at least the name :)

We just needed a little help from the aftermarket tuning market to make the current ones shift as they should, Don't know if the team that performs the calibration in the current transmissions, is the same they use for the trucks, which would explain why they didn't calibrate things up with more performance in mind, damn it even my wife's 2009 Honda Oddy shifts better than what my G8 did in stock trim. Granted, the Honda is not a performance oriented sport muscle car, but is not like 6lxxe trans aren't strong enough to hold it together lowering the shift times and increasing shift pressures here and there. i know they wanted reliability, but geez, how much more TM the trans calibration team think we can handle? we have to let them know we bought a V8 high performance powered car, not a Chevy Malibu :gears:, The Camaro and Vette folks have the same complaint out of the stock trans calibration.
 
#17 ·
These cars with just a good tune especially in the transmission is like night and day.
 
#18 ·
Well... If you don't ever get enough saved up for the tune I have a cortex for sale!!!!! I'll give ya a good deal on it, if need be. Other wise, if you have the money definitely get a tune from Pat~!
 
#19 ·
I am so darn excited to get home (at my Sister-in-Laws now) 500 miles away from my G8for the holidays. Hope the stinkin snow is gone when I get home.. I am ready for a better shifting G8GT. They are horrible shifing beasts from the factory. I could hardly believe it. (I bought my car sight unseen before driving it...and not knowing how sloppy the shifting was) The last automatic sports car I had was a 1975 Trans Am 6.6 litre that shifted a hell of a lot better than my G8. GM missed the boat on the calibration.

I think Bluegoat is right...a dealer relearn would simply reuse the sloppy factory calibration.

I immediatly noticed the difference with a Cortex tune with under 10 miles on the car.

I also think AFM is gimmicky...just thought I would throw that in! ha.
 
#26 ·
You’re very welcome, AllenK!!! How was your Christmas?

Michelle, GM Customer Service
Very,very rainy and stormy to start with,and then it changed to freezing rain and snow. It was pretty,but I don't care much for snow and ice. Too dangerous to get out in. We had to cut short Christmas at my Grandma's due to weather. She's 94 and in awesome health,but I know she can't live forever. Hope yours was great too.
 
#29 ·
I’m sorry you had to cut your Christmas short with the weather. I hope you’re ice and snow free today. In my area, we could use some snow as the winters have been very snow-less. LOL

I hope the weather is better in your area to bring in the new year.

Michelle, GM Customer Service
 
#36 ·
I’m sorry you had to cut your Christmas short with the weather. I hope you’re ice and snow free today. In my area, we could use some snow as the winters have been very snow-less. LOL

I hope the weather is better in your area to bring in the new year.

Michelle, GM Customer Service
Very unusual weather for both of us Michelle!

I thought it took a while for my Dad's '07 Silverado to downshift,but the G8 is definitely worse. I'm with ExpLiciTSainT and Sheffield Steve.
 
#31 ·
I'm with you on not wanting an 8 speed on a six liter V8. Maybe great on a 4 banger with 1.5 liters but a waste of time on something like a G8

I think our cars would have been better with a 5 speed to be honest, although this tranny is basically very good as are GM's in general.

i.e. It's no coincidence that GM transmissions have been used on all the best cars in the world. (Ferrari, Rolls Royce, Bentley, Cadillac, etc)
 
#32 ·
Agree for the most part although I wouldn't include Cadillac in that list, plus its been a while since they used the old GM trans in the Ferrari, Bentley, etc... If I recall it was the old TH400 and 4L80 before those marques switched to fancier transmissions.
 
#34 ·
I wish Sport Mode would see sport driving and stay in the lowest gear possible until you shift back to Drive. I think people get Sport actually means sport. My other complaint is input response. The amount of time it takes to initiate the shift. It makes it hard to set the steering wheel in the right direction during a shift because it's not predictable.
 
#40 ·
This transmission (6L80) is basically a truck transmission, rather than a performance transmission. With a stock engine, this thing will pretty much last forever, while delivering decent mpg.

Performance wise, it's heavy, complicated, expensive to fix, and seems to have a lack of aftermarket support compared to the tried and true GM trans from the past.

I would be happy with a nice built 4L80 or TR6060 in my car. A Turbo 400 is the way to go if you want to put serious power down with this car.


Sent from my iPhone using AutoGuide.com App
 
#41 ·
Lol, that's probably what your tuner told you because they don't know any better other than to run them with zero TM anywhere, and tell you when the trans goes kaboom, that it was because it's a truck trans with no performance in mind. Do you have any idea how people abuse this trans with simple things like a handheld device with ****ty settings ? and how many are breaking at those power levels.

Can you shorter the shift times in a stock 4l60e/4l80e trans, increase shift pressures in stupid amounts, cut all form of TM, and still be behind 500hp applications , peeling tires and leaving 3 miles of black marks because it's cool?, without shift kits or internal upgrades ?, shifting at 6500-6800rpm if desired ?, behind single clutch torque converters that hate factory locking/slip, while still using the same pwm factory approach to lock the converter ? How can you even think it's not a performance trans ?, sure it's not a BMW /Nissan GTR Double clutch Auto trans, but the 6l80e/90e are better transmissions in stock trims when compared to the previous models, and still, it takes more for the ****ty tuner to brake them in stock trim, unfortunately, not many people doing aftermarket for them, main reasons ? they know the ****ty tuners would brake them, and some companies haven't found a way to make money out of the parts that seem to wear the most, most of the rebuilt kits come with stock clutches, or you have to pay a small fortune from the other company who rates at 800/1000hp, who knows what do they use for parts, but they have confidence in the build, which is good is you can afford them.

Most of the issues in this trans are tuner related, keep that in mind if you're new to the forum,

Something i agree with, in high power applications, the TH400 still rule the world :) , at 500rwhp, the trans seems to hold very good with some basic tune care, and no trans kits of anytype, eventually it'll have to let go, but it's not that easy if the tuner knows what he/she's doing. We have folks at 600-700rwhp still on the stocker, granted, this people don't daily drive their cars, but they sure have fun in them :)
 
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