That's right. That also what I said above, that the step appears in later version that were posted on this forum. One was posted by you. Others posted too. So we know it was added, we know other dealers do it, and we know they get reimbursed for it by GM.

 

You are lucky it the techs are even using a manual. I was a lube tech at a Chevy dealership while I was in automotive school. Most used Prodemand or all data for any service information and nothing special was ever done unless specifically asked and an appointment was made. wet dump dry sump never mattered. Oil was drained, whatever Prodemand says was pumped back in and sent on it's way. Service manager only allowed 18 mins for oil change, tire rotation on non staggered wheels and inspection. I always told friends to schedule a A level tech for any Corvette maintenance period.

 

^^^
Yep, as you describe, unfortunately that is the worse way to refill an engine with oil. My 4 volume C7 service manual says what I was taught ~70 years ago when I helped my Dad change oil and what I have always done: FILL TO THE DIP STICK LEVEL. The C7 service manual says the volume in a table is only an estimate, underfill and check the dip stick level.

Both the C7 and C8 require the oil to be at 175F to check the level. That means running the engine until it reaches that temp. Would have killed your 18 minute goal! Techs usually work on commission and beating GMs allotted time for a task. Much easier to set a dial on a pump from a 55 gallon of “whatever oil” is in the oil change bay than going to parts department and lugging 8 quarts of the “right oil” back to the work station!

SIDEBAR
I changed my own oil in my prior 5 Vettes so it was done right. FREE was not worth the risk for my two C7 dry sumps! Now have a great tech. Watched as he changed engine oil twice in my C8. Took the time to start the engine check dash temp reading before checking and final filling to max level. As noted in the owner’s manual it does say Max and if above, drain to the Max level! Unfortunatly some owners think if some oil is good more must be better!

 

Due to the lack of any evidence from GM that their requiring a valve flush at each dct filter change was a "mistake" written into the repair/service procedure im wondering if the real mistake was that there is a dealership out there with techs not doing this and dozens of cars out there with improper filter changes done.

 

What is your training since most techs didn't go due to Covid. I have a list for my State from Corvette Concierge of those that did. Sadly dealers haven't sent most techs. Read on where other techs that have gone state IT'S required. Not counting dealers trying to give me wrong oil fir change or telling me car takes 10 quarts confused because LT1 on Camaro takes 10.

 

Dozens? At the stated rate of "2-3 day", that's 15 per week! And then there are the" replacements" and "overhauls". Overhauls?

 

Since the DCT hydraulic system flush is part of the DCT filter change procedure there won't be any evidence that it wasn't performed. The procedure says to perform the flush, the tech certified he did the procedure, and the paperwork reflects that.

 

^^^

There was a post from someone who bought from MM that was recently told they only do a flush IF there are DCT issues not with just a filter change. Was very surprised as they sell a lot of Vettes. He posted he was hoping they would in his case siNce he had DCT CELs. Don’t know if they are billing GM saying it was done or not.

 

My understanding is there is a single billing code for performing the first service which includes engine oil/filter and DCT filter change. I don't think they get into the details of which steps in the procedures were performed.

 

Raises a related question doesn't it? What happens when a customer or GM is billed for a procedure, and the technician decides to skip a step, or do it differently because he thinks its a mistake, or is told by the service manager it is not necessary or whatever reason. What recourse does a customer have? My view of the suggestion that this particular step is a 'mistake" is that it should be performed anyway, as long as that step is in the service procedure, unless or until there is an actual bulletin from GM saying to skip the step or the step is removed from the procedure by GM. And actually, since this was an important procedure that was added, it may very well be that there is a bulletin about the added procedure. Anyone know? A GM service facility should not make up its own view of what is and is not supposed to be part of the procedure. But then, above, we have someone stating that some facilities don't even have or use the GM service manual procedures.

By the way, the term "Hydraulic System Flush" that appears in the version of the Service Procedures that was posted by Jerry U and others does not appear as a "procedure" in the version of the 2020 Service Manual that I have but there is a list of seven "Transmission Service Cleaning Procedures", each of which is called a "Hydraulic Control System Cleaning Procedure" , each of which lists one or more "Transmission Control Solenoid Valve" numbers. A total of 13 different Transmission Control Solenoid Valves are addressed by these 7 cleaning procedures. And these are called out in various diagnostic procedures. There are more valves than that in the transmission too. My point is this - my observation, based on looking at the version of the manual that I have, is that when a service procedure, such as "Hydraulic System Flush" is mentioned or called for, that procedure (the detailed steps) is found elsewhere in the manual, by that exact name (and with the proper software the procedure called for can be clicked, taking the technician to that procedure). The absence of it from my version (I searched on that term) suggests that it was added as a procedure in a later version of the manual, and then it was added as a first step to the transmission filter change procedure. And my guess is that the procedure combines one, or more, of the existing Transmission Service Cleaning Procedures - and could possibly add others. If someone on the forum has access to the later version where the Hydraulic System Flush is called for, then it could be verified that there is also a procedure in the manual by that name.

 

^^^
Yep agree a dealer for whatever reason who doesn’t follow the prescribed GM filter change procedure is wrong! As I have mentioned and posted a pic of mine being done in August 2021 I was shown on the techs GM service computer info they pay to access:

• prior to the DCT filter being changed, perform a flush
• definded the flush was needed to put possible debris into the filter housing and filter before replacement
• I watched and looked at the Techs PC screen connected to my C8 via the OBD port as the GM software performed the flush
• just recall the last screen saying flush completed

The tech at the small Chevy dealer who did mine does few C8s so has an incentive to look up the procedure. He was trained on the C8. I recall talking with the dealership owner who told me he bought the required C8 service tools, sent the tech for training and he elected to go himself to Spring Mountain that was offered as part of the C8 service commitment.

That is why I was surprised to see a large Covette dealer like MacMulkin mentioned in a customer’s post say they only do a flush if there is a DCT issue. Frankly a large Corvette dealer who does many DCT filter changes might have an incentive to skip a somewhat time consuming step.

PS: I don’t recall seeing other than the word “flush” in the GM prescribed filter change proceedure.
I also don’t have any information related to the poster’s comment about what he was reportedly told by MacMulkin re DCT filter change steps they use.

 

My launch x431s did it without issue. That's specifically why I bought it. Best thousand bucks I've ever spent.

 

Seems like I'm always seeing this argument here on the forum. Flush is only if you have transmission problems / flush needs to be done at each filter change. Does anyone know how to get a definitive resolution to this question? I know it is the first step in the GM filter change procedure but others say that is a mistake and/or GM just hasn't made an update for clarification yet. Is there any way to get an "official" answer for this debate?

And by "official" I don't mean second hand or anecdotal information (Jerry U).

 

I share your interest in getting clarification. But when you say "others", as far as I know it was a single poster who said he was a technician at a dealer, that said it was a mistake. Most of the other cases cited appear to be from dealers that just don't follow the procedure - either they dont know about it or they just ignore it. Its hard to give credibility to those situations since, based on the forum, dealers give wide ranging answers regarding when you should do the first oil change, whether you can pay for the first one and postpone the free one, and on and on.

Best to follow the existing documentation in my opinion. The procedures are subject to change regardless of whether or not they are mistakes. For example, we know that the Hydraulic System Flush step was added to the filter change procedure, because earlier versions (I have one) of the procedure do not have it. In the future, they could choose to remove it if they make improvements to the transmission that negate the need (regardless of whether it was a mistake or not). But technicians and dealers should not, on their own, decide to modify a procedure because they think it might change regardless of the reason. As a minimum they should have a service bulletin.

 

Just as @Andybump above said there was one technician who claimed the official gm dct filter change procedure was "mistaken" in its requirement for the valve flush.

When asked to see any documentation at all that indicates that gm considered this requirement a mistake he produced none.

The logical conclusion from this is that like many people who realize they themselves have been performing a procedure incorrectly on customer cars you can either quickly admit it and change your behavior or you can claim "....ummm we don't have to do that....i heard it was a mistake that its required.". The other option is the technician"heard" from someone its not required which should always be verified. Always follow the written procedures and subsequent bulletins and never change your work practices based 'i heard". That's the kind of thing that can down an airplane.


If it truly was a mistake gm would issue a bulletin stating so. This is normal procedure and required. No such bulletin exists. Simply reach out to @C3zero and ask to see the techlink info stating its a mistake if you want to verify its not the case

 

So, this thread has been active for exactly a month and we still have no definite answer/response from anyone in authority. Before my car goes to MM for a filter change (not due until next year) I would like to know what their current procedure is, and if it is to not change the fluid, I would like to see WRITTEN evidence from GM stating so. Seems to me that with all the reported transmission problems this is an extremely important question.

How do we get their attention?

 

We definitely do have it in writing ... directly from GM techlink...its a filter change and valve flush.

Fluid change is different procedure not discussed in this thread btw

 

Not sure what you are talking about regarding changing of the fluid. Transmission fluid is to be changed at 45000 mile (per the owners manual), or every three years (per the owners manual), or when the transmission fluid life indicator says (per the owners manual). And every 24 hours of tracking. All of this is in the 2023 Owners Manual. There is has never been anything about changing the transmission fluid earlier than that. You won't get a list of everything that you are not supposed to do. Anyway, what is in writing, and is posted just above, is that the Hydraulic System Flush Procedure is step 1 of the Transmission Filter Change procedure which is to be done at or near, but before 7500 miles. The Hydraulic System Flush Procedure does not mean a fluid change. It is a computer manipulation of the transmission solenoid valves, with a goal of freeing any trapped debris, which is then moved to the transmission fluid filter, prior to changing the filter.

 

Sorry, I was confusing a "flush" with a "drain".