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Say you're ready for your 3 year fluid change and you have 21K miles on your car and you put about 5K miles per year on it. You have the following options:
Change the fluid (without changing your filter), and change the filter at the required 22,500 mile interval. This is the strict interpretation of the manual. Change the fluid and filter, and change the filter again at 22,500 miles. This would also be in compliance with the manual.
Change the fluid and filter, and change the fluid and filter after about a year again at 22,500 miles. This would also be in compliance with the manual. Change fluid and filter, and call the filter good until the next 3 year fluid change interval when you have ~26K miles on your car. This would be in compliance with a normal interpretation of a service schedule. Postpone the fluid change until you hit 22,000 miles even if you exceed 3 years and then change them both. Since there is no tolerance on the 3 years this would be a grey area.
Which would you do?
And I've never out a dirty oil filter back on a car. But I've never removed an oil filter that I didn't intend on replacing either. And, yes, I've changed engine oil on a car without replacing the oil filter when changing the oil filter wasn't required.
At 6100+ miles in two years I will most likely never meet the mileage requirements. I will follow whatever the 2021 Owner's Manual says to do when it says to do it. If I change fluid in anything that goes through a filter I'm changing the filter too.
At 6100+ miles in two years I will most likely never meet the mileage requirements. I will follow whatever the 2021 Owner's Manual says to do when it says to do it. If I change fluid in anything that goes through a filter I'm changing the filter too.
Sounds like your are saying you would change the fluid and filter at 21K miles and then change the filter again at 22,500 miles.
I think most people would either change the fluid (without changing the filter) at 21K miles and change the filter at the required 22,500 mile interval or change fluid and filter at 21K miles and call the filter good until the next 3 year fluid change interval at ~26K miles
If I kept my C8 Z51 for another 3 years (hopefully not will have an E-Ray) I would also change the DCT filter with the 6 year fluid change. Would not have enough miles in 3 years to require a DCT filter change. Why not the Labor is small and the flush is worth getting out and small “stuff” that might be ready to clog a small passage. The main labor is lifting the car and removing the aluminum and probably the composite aero panel behind it to make it easy to remove needed to drain all DCT. The extra cost for the filter kit is ~$200, so imo worth the cost. Enough DCT minor issues solved with a flush. With doing as a precaution.
Jerry, have been looking much at the 2024 Manual that has the E-ray in it? I started reading that a bit, and there is a whole lot of new stuff that most of us ICE owners are not aware of and not familiar with.. And example it has a whole separate cooling system for the propulsion battery pack. It uses DEXCOOL. There is an interesting radiation exposure statement. The front hybrid drive unit has its own fluid that requires changing. I can only imagine how the discussion about maintenance will unfold on the E-ray site.
Sounds like your are saying you would change the fluid and filter at 21K miles and then change the filter again at 22,500 miles.
I think most people would either change the fluid (without changing the filter) at 21K miles and change the filter at the required 22,500 mile interval or change fluid and filter at 21K miles and call the filter good until the next 3 year fluid change interval at ~26K miles
I'll do it however the calendar dictates. GM has dates on the maintenance schedule for a reason and I would bet they could care less about the mileage especially on a Corvette. I'll be in an extended warranty after my three year mark. I won't risk that either. Hell - I had my C5 for 13 years and only put 22k on it. I regularly changed the oil and actually replaced a set of Goodyear run flats that had plenty of tread on them because of the tire manufacture date on the sidewall.
I'll do it however the calendar dictates. GM has dates on the maintenance schedule for a reason and I would bet they could care less about the mileage especially on a Corvette. I'll be in an extended warranty after my three year mark. I won't risk that either. Hell - I had my C5 for 13 years and only put 22k on it. I regularly changed the oil and actually replaced a set of Goodyear run flats that had plenty of tread on them because of the tire manufacture date on the sidewall.
Yep - the maintenance people love to see me!
I don't understand what you are saying about the mileage. The DCT filter change is strictly mileage based, it has nothing to do with time. So in the example I provided you would wind up repeating the filter change in another 1500 miles (less than a year) to stay in strict compliance with the mileage interval in the manual. Isn't that what this discussion is about?
Not sure what was meant by "calender" vs "mileage". Wish it were simpler. One could make this stuff up, but since we have an owners manual we don't have to: Based on the data we have now, the DCT filter is changed for any of the following (these are based on what is in the 2023 and 2024 manuals):
1. 24 hours track use
2. at 7500 miles (+/- 500 appears in the procedure but not the manual), then at 22,500, then every 22500 after (which could also mean every 22,500 since the last change).
3. When the filter life monitor says so.
4. Within 620 miles of when the change transmission fluid soon appears (not a typo - that is how it is stated in the manual).
The fluid is change for any of the following:
1.24 hours of track use.
2. 45000 since last fluid change.
3. Whenever the change fluid life monitor says so.
4. At least every three years from last change.
Last edited by Andybump; Sep 12, 2023 at 04:16 PM.
I’ve must of read hundreds of DCT replies to a dozen threads on this topic. The more I read the more I got confused because opinions (or “statements of fact”) are all over the board. Wish I hadn’t read any of them but that rocket left the launch pad.
So I’m going to follow the owners manual after all that’s what counts as the official maintenance of record.
Regardless if the DCT filter was change prior to 7500 miles it must be changed at 7500 miles (+- 500 miles)
The DCT fluid (unfortunately) is to be changed every three years or sooner (if the transmission fluid life percentage monitor says it time to change it), whichever comes first. If the vehicle mileage is near the canister filter replacement interval, replace the DCT fluid and DCT filter.
I’ve must of read hundreds of DCT replies to a dozen threads on this topic. The more I read the more I got confused because opinions (or “statements of fact”) are all over the board. Wish I hadn’t read any of them but that rocket left the launch pad.
So I’m going to follow the owners manual after all that’s what counts as the official maintenance of record.
Regardless if the DCT filter was change prior to 7500 miles it must be changed at 7500 miles (+- 500 miles)
The DCT fluid (unfortunately) is to be changed every three years or sooner (if the transmission fluid life percentage monitor says it time to change it), whichever comes first. If the vehicle mileage is near the canister filter replacement interval, replace the DCT fluid and DCT filter.
This is what is in my 2021 manual and what I'm following.
Jerry, have been looking much at the 2024 Manual that has the E-ray in it? I started reading that a bit, and there is a whole lot of new stuff that most of us ICE owners are not aware of and not familiar with.. And example it has a whole separate cooling system for the propulsion battery pack. It uses DEXCOOL. There is an interesting radiation exposure statement. The front hybrid drive unit has its own fluid that requires changing. I can only imagine how the discussion about maintenance will unfold on the E-ray site.
Yep saw the additional coolers at walk around at the Revel. Best explanations were by Aaron Link. As you note there is coolant for the batteries, a combo for the electric power module and the electric motor with it’s own pump in the front.
The E-Ray like the Z06 has a 3rd coolant rad in the front center that doesn’t have an AC Condenser in front. There is a dealer installed SA option ($895) has 3 screens and uses I believe 8 3M tape brackets. They have a video showing install that requires removing the front bumper. Had me concerned becase in addition to being time consuming they show putting painters tape in key spots to avoid paint chips. Then found CCG sells the same 1/4 inch mesh with 5 screens. They cover 2 open areas SA does not. It’s only $150 and install is all from the bottom similar to the standard C8. Bit more work as some of the plastic duct work has to be removed but all attached with screws and some plastic rivets.
Have not studied all the dash display options. Too many and will wait until mine arrives if ever I can order!
Have pics of all coolers and pump but in Chicago at our annual Trade Show and no pic files on my iPad.
Yes, I changed my DCT filter at 4600 miles and I have written confirmation from GM (twice) that I don't need to change it again until the next service interval is up. And I had it confirmed again after the verbal statements about changing it early came out. But I only knew to do the first confirmation because of the increasing DCT filter change intervals in the maintenance schedule (I asked before I even had my car). Most owners wouldn't delve into the schedule as much as I did. And I got the second confirmation after I actually had the filter changed and had a hard mileage. But anyone that doesn't monitor these forums wouldn't know to do that.
After his discussion I decided to ask GM a fourth time and forwarded them a copy of the page in the service manual that has the 7500 +/- mile requirement. I'll report back on if they quadruple down on their earlier answers or if they change their tune.
I said I'd report back about about what GM said regarding change my 2020 DCT filter at 4600 miles and not changing it again at 7500 miles. As expected they quadrupled down on their position but wouldn't give it to me in writing (I have it in writing from two of the three previous inquiries). I sent them the following in an email:
Below is my understanding of our conversation.
What I have been told in the previous case is still correct. The attachments I sent you were for the 2023 and 2021 model years and they do not apply to the 2020 MY Corvettes. The maintenance schedule has not changed for the 2020 MY. It is acceptable to change the 2020 DCT filter at 4600 miles and not change it again until the vehicle mileage is at 22,500 miles. This will not jeopardize the warranty or put the transaxle at risk. You cannot send me anything in writing to document this conversation but the recording will be retained.
If I do not hear back then I will assume my understanding of the conversation is correct.
I said I'd report back about about what GM said regarding change my 2020 DCT filter at 4600 miles and not changing it again at 7500 miles. As expected they quadrupled down on their position but wouldn't give it to me in writing (I have it in writing from two of the three previous inquiries). I sent them the following in an email:
Below is my understanding of our conversation.
What I have been told in the previous case is still correct. The attachments I sent you were for the 2023 and 2021 model years and they do not apply to the 2020 MY Corvettes. The maintenance schedule has not changed for the 2020 MY. It is acceptable to change the 2020 DCT filter at 4600 miles and not change it again until the vehicle mileage is at 22,500 miles. This will not jeopardize the warranty or put the transaxle at risk. You cannot send me anything in writing to document this conversation but the recording will be retained.
If I do not hear back then I will assume my understanding of the conversation is correct.
Below are the attachments I sent GM:
I read all of your post about changing the filter @ 4600 but not at 7500 miles because you have a conversation documented/retained from someone at GM who says it’s OK you don’t/didn’t change it @ 7500. My question is the DCT filter costs a mere $112.00 vs the cost of a replacement transmission estimated to be $15,000 so why take such an enormous risk should you face a transmission failure? After all unless the person was from GM warranty team who has the final say it may not matter you got a conversation documented.
I read all of your post about changing the filter @ 4600 but not at 7500 miles because you have a conversation documented/retained from someone at GM who says it’s OK you don’t/didn’t change it @ 7500. My question is the DCT filter costs a mere $112.00 vs the cost of a replacement transmission estimated to be $15,000 so why take such an enormous risk should you face a transmission failure? After all unless the person was from GM warranty team who has the final say it may not matter you got a conversation documented.
Changing the DCT filter without having the hydraulic system flush performed wouldn't comply with the procedure so it wouldn't ensure warranty coverage.
This shouldn't be that hard. If GM had conveyed all the current information to me initially I would have changed it at 7500 miles. And even if I change it now I have missed the 7500 mile window and there is nothing that states I would be better off from a warranty standpoint.
I have given the GM team every to discuss the issue with me. If someone knows how I can contact the GM warranty team directly to discuss the issue I'm open to it. GM just says that the factory trained technicians at a Chevrolet certified service facility are the ones that are responsible for answering the question. And they have said I didn't need to change the filter again at 7500 miles.
I have written communication from GM that my warranty isn't in jeopardy. I think I have plenty of documentation to refute a warranty denial because of improper maintenance.
Then perhaps GM owes everyone a new owners manual as its listed in the GM Service Information viewing of the owners manual. The one in SI matches the actual book 99% of the time word for word except for this apparently. The 2023 book just states "must be changed at 7500mi".
Nothing there says you can't change it early, like you can every other fluid, or that if you change it early you need to change it a second time between 7,000 and 8,000 miles.
I'm not interested in paying a whopping $800+ to change my DCT fluid. How can I get a hold of the tool to DIY, or an independent mechanic that has the tool, to perform the valvebody flush procedure?
I refuse to give my business to a manufacturer dealer network that is trying to monopolize service. And this is why we need "Right to Repair" laws in every state: www.repair.org/policy
You don't need to do the valve body flush procedure during the fluid change. Only as part of the required DCT filter changes at 7500, 22,500, and every 22,500 miles thereafter.
EDIT: The above is what the 2020 through 2022 OMs say. Apparently the 2023 & 2024 manuals are different.
The only tool that anyone has identified that performs the specific GM flush is the GM software. That is available to independent shops, but it's expensive, so only a shop that works on a lot of GM cars is likely to even consider licensing it. How can you find a shop that does? Start making phone calls.
Last edited by Red Mist Rulz; Sep 16, 2023 at 03:37 PM.
Agree that we need right to repair laws. But in this case, there are scan tools available to perform the Hydraulic System Flush, as well as other procedures. Someone or more will post some available tools - I don't have one. The Service Manual information is available from Helm inc. If I were going to perform the various maintenance services, I would obtain an up to date Service Manual. The car is complex and there are details in the service procedures that are important - its not just the HSF.
There are scan tools that perform SOME KIND of flush of the valve body. There are none that do it as a single process, and since we don't actually know exactly what the GM software is doing we don't know if any of the scan tools actually do the same thing. Good luck arguing with GM if they say they're denying warranty coverage on the DCT because you didn't follow the recommended procedure.
Nothing there says you can't change it early, like you can every other fluid, or that if you change it early you need to change it a second time between 7,000 and 8,000 miles.
Another interesting thing is it doesn't say when the break-in period ends. Having the first change at 7500 miles, the second change 15,000 miles after that, and then every 22,500 miles thereafter implies the DCT may not be fully broken in until after 22,500 miles.
Not sure what was meant by "calender" vs "mileage". Wish it were simpler. One could make this stuff up, but since we have an owners manual we don't have to: Based on the data we have now, the DCT filter is changed for any of the following (these are based on what is in the 2023 and 2024 manuals):
1. 24 hours track use
2. at 7500 miles (+/- 500 appears in the procedure but not the manual), then at 22,500, then every 22500 after (which could also mean every 22,500 since the last change).
3. When the filter life monitor says so.
4. Within 620 miles of when the change transmission fluid soon appears (not a typo - that is how it is stated in the manual).
The fluid is change for any of the following:
1.24 hours of track use.
2. 45000 since last fluid change.
3. Whenever the change fluid life monitor says so.
4. At least every three years from last change.
The 2021 manual doesn't have that 1000KM wording in it. It says to change the filter only if the mileage interval for the filter change is near. GM hasn't notified owners of earlier cars that the service requirement has changed. Will be interesting to see what Criswell says when I hit the 3 year mark. I will probably only have a few thousand miles on the DCT filter (after changing it at 22,5K) when I hit the 3 year mark. Does GM really expect me to change it again at that point? And don't tell me it's important to get the 6 oz. of dirty fluid out, when the fluid change leaves 2 liters of dirty fluid behind.
Even worse, the change fluid soon warning seems to be based only on mileage, and not time, so when I have the fluid changed at 3 years I won't meet the "Or" clause above. The "Change Fluid Soon" won't have displayed on the DIC at all.
GM seems to be completely incapable of adequately communicating maintenance requirements. Even a lot of dealers have no idea what the requirements really are.
Hmm, a bit of semantics saying it’s not in the owner’s manual as it is clear in a GM bulletin (see below) that the only formal GM allowed deviation is +/-500 miles from 7500 for a filter change. I think it is silly to say if you it changed say at 6500 miles MUST change again 500 to 1500 miles later. I have argued a won GM warranty issues but for ~$20,000 replacement cost DCT would be Foolish IMO to take a chance.
GM has never provided that bulletin to owners. If I didn't hang out on forums, I'd have absolutely no way to know about this revision to the service requirements. And since the bulletin didn't come out until I had 16 or 17K miles on my car, it is meaningless. How am I supposed to go back in time and have the fluid changed at 8,000 miles? GM can't hold me to a service requirement that didn't exist when it would have applied to my car, and which even the dealer couldn't have known about.
Nothing there says you can't change it early, like you can every other fluid, or that if you change it early you need to change it a second time between 7,000 and 8,000 miles.
The manual says “must be performed at 12 000 km (7,500 mi)” it doesn’t say or earlier. The language is very clear and non-ambiguous. In addition the manual states fluid must be changed “every three years”.
The manual says “must be performed at 12 000 km (7,500 mi)” it doesn’t say or earlier. The language is very clear and non-ambiguous. In addition the manual states fluid must be changed “every three years”.
Interpreted literally that means if you change it at 7499 or 7501 miles you didn't follow the manual. Interpreting the requirement using common practice as done with other vehicles you have some unspecified leeway on the interval and if you change it earlier than at the specified interval you just add the distance between intervals to your current mileage and perform the next service at that mileage point. There is nothing in the C8 owner's manual that says the maintenance intervals need to be interpreted differently than other vehicles.
And apparently Chevrolet Customer Care and many dealers interpret the requirements traditionally instead of some special for the C8 interpretation.
