falcon5619

Nah, with the A8 AFM will kick in regardless of drive mode you are in. The only way to to turn it off is to put the trans in manual mode and paddle shift. You can see this for yourself on the dash when you set it to that screen that shows your mileage and at the bottom is a V4 or V8 symbol. Just drive around and you will watch it switch from V8 to V4 mode all time. It will stay at V8 mode while at idle and then once you are steady cruising you will see it switch to V4 (AFM) mode.

falcon5619

They could but won't. They need AFM to meet the fuel regulations. It can be permanently tuned out by a tuner but you then put your warranty at risk. The Range device is so popular because for under $200 you can plug it in and it disables AFM from engaging while not modifying the ECU tune.

falcon5619

Another thing to keep in mind is that this TC shudder issue shows up on A8s all across the different GM vehicles using it. Denalis, Tahoes, Trucks, Camaros, etc. I had a new 2016 Camaro 2SS and sure enough right around 4500 miles I am cruising on the highway and here it comes...call it shudder, rumble strips, whatever but it is very disconcerting and at that point you know it will only get worse from there. Triple Flush, then order a new TC and pray it doesn't come back. Some try to get a Range device on the car right after they get a new TC to help avoid the issue from repeating. Now, if new fluid is working then so be but it must be performing some magic to help reduce the shudder to lower levels or whatever but I hope it offers a long term fix.

retcav1sg

I'm really wanting and am in the market for a C7, it would be vette number 12. As I'm reading and researching, this AFM issue really has me second guessing a purchase. Am I correct in understanding that this is an isolated issue not a "when not if" issue which has been magnified by those coming to the board to sound off? Surely the percentage of problem cars has to be quite small. Are the 2014 models with the A6 transmission afflicted by the same issue? Any help/reassurance/opinions would greatly appreciated.
Mike

Sellout

My 18GS hasn't had any shuddering that I can feel. I'm at 7800 miles now and the only issues I can relate to AFM are a squeak noise from behind me when it switches to V4, and a constant tick at idle that I've been assuming is coming from one of the AFM lifters. This tick is too slow to be the fuel pump in my opinion, but they say it's normal.

The shop foreman at my local dealer is putting in a request for help from the engineers to diagnose that squeak sound now.

NSC5

The tick from the fuel pump is a slow tick at idle and sounds very much like a lifter tick since it is also driven via a camshaft lobe. As the shop notes it is normal. My 2016 Z06 is the third GM vehicle I have owned with a direct injected gas engine, my 2008 CTS was the first and GM did a lot of sound deadening since direct injection was still relatively new and they were trying to control the level of this "new" sound but now that it has become such a commonly used system there is far less attention paid to attenuating the direct noise from the pump itself and further distributed via the common fuel rails. It can be disconcerting for those new to these engines but it is a normal operating characteristic of the engine.

The squeak from the additional AFM sound control valves has been reported by others and replacement will cure it at least for some time. These valves live in a rough position in the exhaust system and don't stand up well to the heat of the exhaust when driven in a spirited fashion and even if they are open they still get hot. They were never used on the Z06 because they simply won't stand up to the heat and those who track the other models cook them regularly.

I would keep your torque converter clutch in good health by either leaving the transmission in manual mode or using a Range module. With AFM, regardless of the magic fluid used, it is a question of when and not if the converter lockup clutch will suffer enough wear to create enough slippage to cause shudder. If you only plan to keep the car for a short time it isn't an issue but if you like your Corvette and plan to hang onto it for some time the slight fuel mileage gain from V4 mode operation isn't worth having to have your car largely disassembled to replace the torque converter once wear reaches the point where friction modified fluid can no longer mask the underlying problem. The use of AFM itself is questionable but the attempt to minimize vibration of the engine running in V4 mode via abuse of the converter clutch was a terrible idea and it is a problem across the GM product line and not limited only to the Corvette.

Cosmo Kramer

Vetteman Jack

GOC

In the A8, does it go in and out of V4 in all modes or just ECO?

NemesisC5

My 2017 Silverado 6.2 with A8 didn't shudder till almost 26k miles, going to dealership tomorrow.
Shudder feels like it's getting worse...feel like I'm driving a POS.

stevesrubyred93

Here is today's update. Dropped of my car a few hours ago and the service manager told me that it did sound like a torque converter shudder.If it is diagnosed with a shudder he said they would do a transmission flush and install updated fluid.I said it was a 18 and should already have the updated fluid. He said it depends on the build date. So apparently there are a ton off these out there that were made in 17.He did tell me if it was a Silverado they would replace the torque converter on the first visit, but not on the Vettes. He told me they receive Silverados everyday with this problem and they had 5 of them in the bays right now,and it might take a while to get to mine. Its not just Silverado's and Corvettes either. There was a Colorado parked right in front of me with a shudder problem that he pointed out to me.So If they are replacing the converters on the trucks, why not the Vettes? Sounds like it's too expensive on the Vettes.I will update when I know more.

Sellout

All modes with the transmission in auto. The only way to avoid it by default is to keep the transmission in manual.

retcav1sg

Yeah...really rethinking if I want to dive into this pool, does the 2014 with the A6 suffer this same affliction?

falcon5619

I have not heard of the A6 experiencing this issue but I could be wrong. Although the A8 has this issue in all the GM vehicles that use it. It is AFM, they ruined a great transmission with that fuel saving tech that really doesn't save that much fuel. Ask the folks using the Range device.

Now, if you like to row your own gears the Tremec M7 is a sweet transmission and you never really hear bad things about it. It sounds like manuals will be collectors items soon so might as well pick one up. :-)

23/C8Z

Listen, the good news bad news here is this...

they know what caused it. They addressed it with the new fluid formulation.

If it needs a new converter? You'll never know the car was apart of the tech is worth a dam.

just get it done and move on.

sucks that some early 18s didnt receive new fluid.

they should be swapping the fluid on delivery so they dont have to deal with this nonsense later.

gm hoping people dont realize it and keep driving lol unreal..

just had my 16 (10 15 build) 8spd Sierra converter replaced and fluid flushed new filter etc at 25k miles. Drives BETTER than new.. no bs. So just have it done (and dont watch).

themonk

it's funny to read that even with all the examples of bad A8 trannies, people are willing to risk it because they don't or can't drive a MN7.

Skid Row Joe

Aside from our physically disabled C7 brethern, I think most of the A8 buyers don't give buying the auto a second thought. They're so happy to get a C7, they never gave the lack of the manual a thought. They've probably been driving an auto for so long, they're probably not thinking straight. I think the majority thought the C7 only comes as an auto trans.

LT4CMG

I’m on the vette, Camaro and Tahoe/Yukon forums. This A8 has been a curse on GM buyers since 2015. Some play it off like it’s “just a handful” of people, but the number of failures are ridiculous. My vette and Camaro are manuals (luckily, no back or leg issues for me, I can enjoy my manuals) and when I was in the market a couple months back for a 16/17 low mileage SUV, the Tahoe was my only option as the Yukon has the dreaded A8 (a whole lot of pissed off Yukon owners on the forums). Let’s hope the A10 story is a better one.

2500 hd

If I start having those issues, I will trade mine on a manual..

NemesisC5

Scheduled my 2017 Silverado 1500 6.2L / A8 for 9-27-18 fluid flush and "diagnoses". General Manager said A6 equipped don't have this issue and so far no issues with A10. In my truck the shudder occurs at TC lockup, usually between 1300-1600 rpm in gears 3 and up where load on engine is higher. It is not "solely" dependant on switching from V4-V8, I monitored this for days and did not not once see the the 2 conditions occur simultaneously. However, I cannot say that AFM did not contribute to causing problem initially.