I have a 2020 C8 with 7,000 miles, and I'm wondering when should I get my first transmission maintenance?

 

if you are on oem fluid you should be changing dct fluid and filter now.

 

Try something really unique like reading the owners manual.

 

Your first service should have been at 3 years old regardless of mileage as a fluid change was due at that time. You definitely need to do both DCT fluid and filter change now.

 

Moved to C8 Tech.

 

DCT externals canister filter: Change it between 7000-8000 miles even if it was changed before, then at 22,500 miles on the odometer, then every 22,500 miles after that, or every 24 hours of track use, whichever is first.

DCT fluid: Change when the fluid life monitor says so, or at 450000 miles, or at least every three years, or every 24 hours of track use, whichever comes first. The fluid life system does not include time, you must observe the three year requirement yourself.

Engine Oil and Filter: Change when the oil life system says so, but at least 7500 miles, and at least once a year. The oil life system includes time, mileage, and a variety of other factors and will normally tell when to change it. But it will never go beyond 7,500 miles or 1 year from the last reset.

 

It's time for a HSF, fluid and filter change.

Call around a few dealers and inquire if they have a Certified Corvette tech and inquire their labor only rate. Supply your own fluid and filter purchased from RockAuto.

Go with 10 qts of the fully synthetic Valvoline FFL-4 fluid and a OEM filter. Fluid change drain amount is typically 8.5 to 9.5 qts, not all will drain out. Valvoline is Fully synthetic at $7:55 per quart versus ACDelco synthetic Blend at a typical dealer charge of $40 qt. You will also save $100 on the filter and would recommend only using the OEM filter, no aftermarkets on the filter!

Been pleased with the smooth shifting fully synthetic Valvoline DCT FFL-4 now for 3 years. Have 37K+ on my 1-owner 2020 trouble free DCT that shifts manually at 7K.

You're outside the 5-year drivetrain warranty. Don't let any dealer try talking you out of using Valvoline 888705.

 

The HSF can also be done by just driving the car. Replace the cannister filter and the fluid then drive it.

At about the 2 minute mark :
From the transcript :

 

Required or not, in updated versions of the procedure for changing the external canister filter, it appears that the HSF has been deleted as step one. It has now been added as the last (not the first) step in the fluid (not the filter) change procedure.

When asked again, the "engineering team" (whoever that was) responded that it is still not necessary for DIYers - in either procedure.

Also, required or not, I do not believe Josh ever said that the fine filter routine running down the highway is identical to the Hydraulic System Flush. Josh described it as "forcing more fluid" through the filter. I'm sure it does that. But the HSF does more than that, according to the description found in the Service Manual. I do not believe that procedure described in the manual could be executed while the car is cruising down the higher. All that said, he still said you could skip it if you are doing it yourself. I never heard anyone from GM specifically say that skipping it would not void the warranty - I think they try to avoid making specific comments about whether something will or wont' result in a denial of a warranty claim. I'm not at all saying its a warranty issue - only that they never explicitly say those words.

Below is the quote from Josh in a Bash in 2024. And also attached is a description of the HSF in the manual. You can compare Josh's description with the description in the manual and judge for yourself whether that procedure, which actuates the solenoid in a specific way, can be executed during normal highway driving. And the updated procedure for the fluid (not the filter ) change showing the HSF at the end, not the beginning, of the procedures.

""The hydraulic system flush does kind’a the way its described. It forces transmission fluid through the fine filter that you replace. So, at a dealership they can hook up the dealer service tool to the and run a routine that will tell the trans control module to do this fluid filter flush. And because the car is already hoisted on the rack, the technician’s already got the panels off, there’s some other work he’s doing, this kinda happens in parallel in the background. So we’re doing it at a dealer visit because we can. And we can take the last bit whatever contamination might be in the oil and get it into the filter before the technician replaces it. Do it yourselfers have become nervous that hey now I can’t do it myself, I don’t have a service tool, I can’t force this routine. You don’t have to do the routine. Like I said we do it because we can, but the fine filtering routine happens during normal driving anyway. In fact, when you’re driving steady state like say down the highway, we run a routine in the transmission that will force more of that fluid through the fine filter. So normal driving is doing this. If you are a do-it-yourselfer, you don’t want anyone else touching your car, you can change the trans filter without running this routine."

 

Yes, I've seen that video before. He says the HSF does a fine filtering routine and he says driving down the road does the fine filtering routine. He never says the driving down the road does EXACTLY the same thing as the HSF. If driving down the road did EXACTLY the same thing then why ever bother doing it at all since the car was just driven down the road to get there and it will be driven down the road when it leaves? And when some people have had DCT problems why did performing the HSF fix them if the exact thing was just done during the drive to the dealership?

Don't get me wrong, I don't believe GM would deny warranty coverage if the HSF wasn't done during a DCT filter or fluid change. I plan on changing the DCT filter myself in the future and I will be doing more DCT fluid changes without doing the HSF. But I do think the HSF has some benefit over driving down the road. Probably a more robust flushing of the system.

 

Its a mystery requiring a little "dobulethink" Or....maybe not. If its really not necessary why was this unnecessary procedure added to the filter change procedure, and why very recently, was it deleted from that procedure, but then added to the fluid change procedure? Why not delete it from routine maintenance procedures altogether? I remain convinced, based on the Service Manual procedure, that it cannot be executed running down the road - the solenoids that are exercised are clutch and fork control valve actuators. And it has been used to successfully resolve transmission issues. But I'm sure it also forces more fluid through the fine filter, like Josh said. The reason Josh gave for running the HSF as part of the filter change procedure (now removed) was to "take the last bit whatever contamination might be in the oil and get it into the filter before the technician replaces it. " So, even though it does more than just force more fluid through the filter, that may the be primary reason they included it in the filter change (and now the fluid change) procedure. And if that is the case, then yes, running down the highway will accomplish the same thing they wanted the "routine" use of the HSF as part of a maintenance procedure.

 

I didn't bother to ask if the dealer did the HSF routine when changing my fluid last fall.

 

I don't think we know exactly when the HSF was added to the fluid change procedure. But it was "relatively" recent. I think we discovered it when @Stoopalini posted a more recent version of the fluid change procedure that has it. I believe that is also when it was confirmed that it is not in the filter change procedure now.

 

HSF is not part of the canister filter change procedure anymore?

GM doesn't know what they want.....

 

Its based on what @Stoopalini found. He has Chiltons version of the manual, which appears to be verbatim whats also found in the version accessed through GM. And I think he also got a couple day subscription to the latest GM procedures, and found that the HSF is no longer part of the filter change procedure. I think he posted both the fluid change and filter change procedures.