Hi everyone, I would like to get your opinion on the transmission fluid service interval based on time.

I have owned a 2015 Stingray since new and have only put about 31k miles on it. The last transmission service was in 2019 when the dealer performed the triple-flush under warranty. Recently, I have started to notice some minor shudder again at low speeds and in lower gears. I have also seen the Range AFM disabler discussed and plan to give that a try as well.

My dealer recommends changing the transmission fluid every 4 years regardless of mileage (I assume this would be a drain-and-refill). Is there a general consensus on the appropriate service interval, considering the history of the C7 A8 transmission and the fact that I am starting to experience mild shudder again?

Any comments, experiences, or suggestions would be appreciated. Thanks in advance!

 

Firstly, I would not be surprised if the "shudder" you are describing is the AFM kicking in from 8-4 and 4-8. Definitely try the AFM disabler.

Secondly, I think every 5 years, regardless of mileage is time for a transmission drain and fill.

Both of those items should help a lot!

 

ATF usually does not go 'bad' over the years but mileage is different. Every time you drive the car some slight wear takes place on the transmission clutches and the converter lock up clutches not to mention the transmission gears themselves.

For a low mileage 'garage queen' you could easily go 10 years and maybe more, the fluid would come out looking as new and any testing on the fluid I doubt would show any great amount of degeneration.

On a low mileage 'garage queen' a 10 to 15 year full flush would still be an overkill.

 

Thanks for the input guys.

I've been using the AFM disabler the past few days and was able to confirm that the car stays in V8 at all times. However, I'm still experiencing some shudder/sticky shifts at low speeds, so AFM should not be the cause. It doesn't always happen, but the shudder can be quite strong at times.

I understand many of your opinions that ATF generally does not go bad easily over time. Given the symptoms, I may still do a drain and fill just to be safe. I've scheduled an appointment with a Corvette specialist indy shop for them to test drive the car and take a sample of the ATF for diagnosis. (The dealer I used before said they would need the car for 1-2 weeks just to diagnose)

This transmission has always had some shudder-related issues in the past. It started with buzzing noises from the torque converter when the car was new, which the dealer addressed under warranty in 2018 with a transmission service (not sure if it was a flush or just a drain and fill). Then the triple-flush bulletin came out in 2019 and the dealer performed that for free under warranty. In 2021, I complained about the low speed shudder again and the dealer recommended and performed a TCM update.

Each time, the work noticeably improved the condition, but the shudder seems to be gradually returning now. I don't think it's any worse than what I experienced before, so I'm hoping for the best.

If you have any thoughts, please feel free to let me know!

 

I would do another triple flush, I am due for one myself.

 

Does the triple flush need to be done routinely?

I see in the bulletin that it only needs to be done once per vehicle, but maybe that’s just GM not wanting to pay for it.

How often do you do it? Are you having any symptoms?

 

I thought the triple flush is to get rid of the old fluid which is too hygroscopic? If you got rid of the old fluid, I would think that all you need to do is a routine pan drop.

 

That sounds correct. However, even the triple flush leaves some of the old fluid in there and the new fluid may still absorb moisture at a slower rate. Too bad the triple flush is rather pricey even if DIY.
Wish I knew more...

 

Well, if you want to get every drop of the old fluid out, you would have to disassemble the trans, clean all the parts out, hot tank the core and rebuild it. While I agree that it is the best way, if I wasn't rebuilding the transmission, I can't say it is economically feasible. You are right that reminants of the old fluid will absorb mositure but I would GUESS that it would not be enough to cause issue and the refresh by dropping the pan would be, while not perfect, satisfactory. Now if this was a Ferrari F80, I would definitely want to rebuild the trans and clean out every drop of the old fluid. I guess the question is how far up the ladder do you want to go? Would it be worth it for what we have?

 

It appears that you drove the car on the original fluid and then again on the second version of the fluid (Black Label). Then finally, you were able to flush the trans with Mobil1 Blue Label.

My best guess is that the TCC (torque converter clutches) are worn and not engaging properly causing the rumble effect.

Replacing a torque converter is a involved procedure not to mention if not done COMPLETELY correct you can have a whole basket full of issues, some very expensive, ie: engine thrust bearing destroyed.

If I were you, at this point I would just do another complete tripple flush with Mobil1 'Blue Label ATF and proceed to monitor the situation.

Best of luck on your repairs.

 

That is correct. Thanks for the detailed response.

I have the triple flush scheduled for 4/6. The dealer is backlogged, so I’ll need to have it done at a Corvette specialist indy shop. They claim to only hire master GM technicians and say they can do a better job than the “kids” at the dealer. They've test driven the car and said the triple flush should help make it a lot better.

Do you have a general recommendation for transmission service intervals based on time? The indy shop told me that if I want to keep the car long term, they recommend a drain and fill every two years regardless of mileage, and a triple flush every four years. That seems a little excessive to me though.

 

They sound like politicians. "Vote for me because my opponent sucks". Makes me wonder.

I'd definitely be leery. I'd perform maintenence at service level and not that crazy schedule.

If you are racing or you tested the oil, that's different.

 

Yeah that made me a little wary. But I’ve seen many people recommend this shop here (other than them being expensive), so I think I can trust them to do the triple flush.

After this, I’ll probably just go back to the dealer and do a drain and fill every 4 years, as the dealer recommends it. I don’t track it, just daily commute.

 

As long as they bill at least 2.8 hours, 24 quarts of the correct fluid and a filter, you should be fine. If the quote is off, we'll.....

 

Yes, that's pretty much what they quoted.

I doubt the dealer changed the filter when they did the triple flush under warranty though.