Once and for all does the DCT fluid need to be changed every 3 years mileage be damned?
If yes tell me this does this mean that I have it changed and then at 7500 do it again.?
This change is time based not mileage based I ask this because there are posts here that say the fluid has a shelf life of what? 3 years or 6 years so every 3 years change the DCT fluid?
So far this is what I've seen posted
OIL/filter 1 year
Cabin Filter 2 years
DCT Fluid 3 years
Whatever at 7500
So if I go by the schedule for me.. OIL/FILTER October 24, Cabin filter due in October 24, DCT fluid October 25,7500 Service whenever. This due to the fact this car was put in service 10/27/22
ALL else fails go by the Manual
Whew hope I have got time to drive this thing in between service appointments This sure ain't the C7

 

Every 3 years or 7500 miles, whichever comes first. The next one after that is at 22,500 miles or 3 years after your first DCT fluid change. If you changed your DCT fluid prior to the 7500-mile mark, yes you do have to change it again when you reach 7,500.

EDIT: Every 3 years for the fluid, and 7,500 miles for the DCT filter. If you replace the filter prior to 7,500, you must change it again at 7,500.

 

The DCT fluid needs to be changed at least every 3 years regardless of how few miles are on it, possibly sooner depending on other factors including mileage.
If your fluid is 3 years old when you hit 7500 miles then it will need to be changed. However you don't have the change the fluid because you change the filter or visa versa, they are on independant schedules.
If you put the fluid in anytime before the expiration date then it is good for 3 years in the vehicle.

 

Walter, I strongly suggest you read the manual and make your own list from the manual. You seem to be confusing fluid changes with filter changes and they are not coupled. But, I have corrected your list from above:

Once and for all does the DCT fluid need to be changed every 3 years mileage be damned?
If yes tell me this does this mean that I have it changed and then at 7500 do it again.?
This change is time based not mileage based I ask this because there are posts here that say the fluid has a shelf life of what? 3 years or 6 years so every 3 years change the DCT fluid?
So far this is what I've seen posted
OIL/filter 1 year - or when the Oil LIfe System says to change it.
Cabin Filter 2 years
DCT Fluid 3 years - or when the Fluid Life System says to change it - or at 45000 mile - or every 24 hours of track use.
Whatever at 7500 - The DCT external canister filter needs to be changed between 7000 and 8000 miles even if changed earlier, then at 22,500 miles, then every 22,500 miles thereafter - or when the filter life monitor says so (if you have 2023 or later). This is NOT a fluid change, it is a filter change. They are not on the same schedule.
So if I go by the schedule for me.. OIL/FILTER October 24, Cabin filter due in October 24, DCT fluid October 25,7500 Service whenever. This due to the fact this car was put in service 10/27/22
ALL else fails go by the Manual
Whew hope I have got time to drive this thing in between service appointments This sure ain't the C7

 

Haven't you asked this question 3 times this month???

 

Yeah, but this time he said "Once and for all"

 

It would appear that the same individuals repeatedly ask the same questions even after they've been answered in detail, repeatedly.

 

golddog Thanks for monitoring my posts Probably have because more questions arise than answers

 

Walter, I get the basis for your confusion. If you look carefully in this very thread you will find incomplete and sometimes maybe confusing answers. Perhaps even my attempts are not working for you. That is why I suggest that you read the manual and make your own list. I provided some pages from the manual with the key service requirements highlighted. It is really not that much, and the majority of what you need will appear on about two pages, regardless of which model year you have. I found it necessary to do this exercise myself. If you make your own list you will have better grasp of the requirements, remember them better, and you will have more confidence in the result.

But they are pretty simple:
1. Change the oil when the Oil LIfe System tells you to. The OLM already includes the 1 year requirement, so you can rely on it entirely. Never go more than 1 year.

2. Change the transmission fluid at least every three year from the last time, or when the Fluid Life System tells you to. Never go beyond 45000 miles between changes. Your Fluid LIfe Monitor does not include time in the calculation so you are responsible for observing the three year requirement. However it does include miles and other factors so it should indicate a change at or before 45000 miles (we only know that the later manuals required a change at least every 45000 miles).

3. Change your DCT filter between 7000-8000 miles regardless of if changed earlier, then at 22,500 miles, then at least every 22,500 miles after. If you have a 2023 or later, you also have a filter life monitor but the same mileage requirements are still stated. Observe the mileage requirements for the DCT filter change.

 

So I pulled up this GM tech link when the New Stingray came out and during the explanation of the new DCT it stated that “ An external transmission cooler (Fig. 24) mounts on top of the transmission to lower the fluid temperature. There is not a required fluid flush procedure and the transmission should not be flushed. It does state that there is an external filter that needs changing but no flush of the transmission is required. Anyone know anything about this? Here is the link I pulled up gm- tech link.com.
The article is from March 1 2020.

 

Sure that was the introduction of the features of the new C8 to the techs in 2020. Are you asking about the term flush? The statement about no required flush is referring to the idea that when a transmission is drained then there is a flushing of the fluid in the case. And there is no procedure for that and it should not be attempted. This has absolutely nothing to do with, and should not be confused with, the hydraulic system flush procedure. It is the reason though, that I frequently point out the need to use correct nomenclature for service procedures. Many folks will refer to the transmission fluid change, which is a simple drain and fill, as a "flush". It is not a flush, it is a simple drain and refill. The hydraulic system flush is a procedure in the Service Manual, it has been mentioned in several techlink articles, and it is, among other things, a step in the DCT external canister filter replacement procedure. It does not involve draining fluid or flushing the case. It is a computer controlled manipulation of the valves in the transmission, with the engine running, that has a goal of freeing debris in the lines and valves and moving that to the filter, before the filter is replaced. It takes about 8-10 minutes.

Attached is first part of the DCT external canister filter replacement showing the call to the Hydraulic System Flush procedure.

 

They are referring to a traditional automatic transmission flush where an external device is used to "powerflush" the transmission with new fluid. People have confused this with the hydraulic system flush which is an internal system flush where a computer manipulates the internal valves to move contamination into the filter.

 

A flush and a drain and fill aren't the same thing. A drain and fill is what the owners manual and service manual call for. A flush process forces all the used fluid out of the system by forcing another fluid through the system under pressure. That new fluid might be just new DCT fluid, or it might be some sort of "cleaning" fluid that then needs to be drained. It's the pressure flush that GM says not to do.

There are a lot o dealers that try to sell their service customers on the need to do a "flush," typically using products from a company called BG. Those procedures are HUGE profit centers for service departments, but can damage your DCT by diluting the called for DCT fluid.

You MUST drain and fill the DCT fluid every 3 years or 45,000 miles, or 24 hours of track use. That's what the OM says.

 

So I understand the use of the correct nomenclature. Essentially they are stating drain the existing fluid and refill at the 3 year mark or 22500 miles?
No flush just drain the existing fluid and refill with fresh fluid? Sorry for the confusion on my part. Thx all

 

If you are replacing the DCT fluid without changing the DCT filter then, yes, it is just a drain and refill with some nuances.

 

NOPE - go back and read again. 3 years or 45,000 miles

 

The DCT Fluid & canister filter change is easy peasy but it's the required hydraulic system flush procedure that's a PITA + costly too. And BTW - your owner's manual is incomplete... while the Service Manual is the best source of GM requirements.

 

The Owners Manual is incomplete in the sense that it does not, and is not expected to, list every step in the DCT external canister filter change. There are other steps of interest in that procedure that are also not articulated in the Owner's Manaul. That procedure also calls a Transmission Fluid Level and Condition Check that involves getting the fluid up to temperature, cycling the gears, then checking and setting the level of the fluid after the filter is changed (because the filter replacement results in loss of a small amount of fluid). And it includes using a procedure initiated by a scan tool called a Hydraulic System Leak test. I don't know exactly what it does, because most of the instruction come up on the scan tool screen, but it would include running the procedure then checking for leaks. Now, do all dealers follow all the procedures? IDK.

A more serious omission from the Owner's Manual is the lack of clarity on the requirement for the first DCT Filter change. As noted many times, the 2024 version of the manual put into writing the verbal statments form GM reps - that filter must be changed between 7000-8000 miles even if changed earlier. That has been in the Service Manual for a while but how would owners of previous models know about that unless they read the forum.

 

I was surprised that there are two DCT filters to change. The second is in the DCT pan, I am going to try and get the part number for it. I did not change it on my 3 year interval and it's really bothering me. Especially since I read about a lot of DCT issues

 

Thats ok, but there is no stated requirement to change that internal filter in the Owners Manual. The Service Manual includes a procedure for draining and filling the transmission - and it does not include removal of the pan and changing of the internal filter. There is another procedure in the Service Manual that does include removal of the pan and replacement of the filter. But there is no indication that replacement of that filter is part of routine maintenance.

I will say that the Maserati MC20, which does use exactly the same Tremec 8 speed DCT does call for replacement of the internal filter every 74560 miles or 8 years. If you like that, then consider that the same car also calls for the DCT external canister filter every 9320 miles or every year.