I have a question regarding the necessity of the DCT flush prior to filter change. As a maintenance nut, I will be doing my filter drop early. I will also be looking at draining and refilling the trans fluid at regular intervals. I know the fluid is pricey, but so is the car. If the filter and fluid is replaced often, is it really necessary to run through the flush procedure? Not trying to stir the pot, just wondering if flushing is absolutely necessary if fluid and filter are changed more than recommended by the OEM.

 

As a 'maintenance nut', if you will be going through the effort to change the DCT filter and fluid regularly, then I think you would be well advised to purchase a reasonably priced diagnostic scanner that will enable you to perform the hydraulic system flush. I would strongly advise that you remove and replace the in service filter first - before doing the flush procedure and then replacing this filter used for the flush again with a new filter. So, the process would be to install a new filter, perform the flush procedure, then drain and refill the fluid and install a new filter again. You will be using a new filter for the flush only and discarding it when the flush is done.

 

Do we have examples that confirm that that iron levels continue to accumulate if the fluid is not changed early? Assuming folks are interested in data - we would need someone who drives at least 45000 miles in less than three years that is willing to follow the scheduled maintenance, and not more, to take fluid samples for analysis at 1000, 7500 and then every 7,500 miles thereafter. And the filters would be changed on prescribed schedule. Then we could see if the levels grow, level out, or whatever. And we could look at the other analysis results too. Do the analyses show the accumulation of all particulates? Or just selected contaminants? I would assume that clutches also shed non metallic debris. Is that detected? I doubt anyone who already believes metal accumulation in the fluid is an issue will be willing to do this.

I think there is plenty of evidence that the transmission is sensitive to contamination, metallic or not. The instructions for fluid change include cautions about contamination of apparatus while filling the transmission, the presence of the fine filter shows that, and the fact there are bulletins addressing failures that include performing the hydraulic system flush are all evidence of that. And there are plenty of forum reports of issues that were resolved by the HSF.

 

Sounds good, thanks. I have 2 filters in stock and have recently purchased a Foxwell scanner. My question was more of a curiosity factor. Thanks again.

 

Do you do this, or do you just change it so often that you skip the HSF? I would be curious about what is found in the "sacrificial" filter when this is done at the otherwise prescribed filter change intervals. Apologies if you already showed that.

 

I have covered this. I did the HSF during my second year or ownership - twice. I cut the two sacrificial filters open and found they looked like new.This was with around 7000 miles and after already having done multiple filter changes and one fluid change. The amount of debris I had been finding in my filters had been trending down by the time I did the flushes. After HSF #2, I changed the fluid as well as the filter.

A visual inspection of my filters is not an analytical process. It’s simply a visual inspection. Did the HSF result in removing wear elements from the unit that would have shown up in an oil analysis? I don’t know.

 

Given the TSB’s related to debris, I would absolutely run the flush as per service guidelines.

As Mitchell_B recommended, and I’ve done previously, use a fresh filter and plenty of cooling fans for the car when you do the flush. I bought a couple of the cheap $15 Amazon DCT filters (they look fine to me) only for flushing use, then replaced after flushing with the OEM Delco filter. I plan on doing this twice, and then the normal flush procedure from then on.

 

Guys - The summary here is service the DCT fluid/filter yearly if you can. I understand this may be an expensive proposition if you are dependent on a Chevy dealer to do it, but, based on everything I and others know, the TR-9080’s shared sump design has characteristics that should be acknowledged regardless of what Chevy bean counters put in the owners manual.

If you have DIY capabilities, use Valvoline 888705 DCT fluid without worry, and the DCT service cost is the same as a synthetic engine oil service.

I spoke with Motul last week regarding details of what was done with Emelia Hartford’s TT-C8 a few years ago, and subsequent work with other high-HP C8 builds, Dodson, etc. I use Motul oils in my motorcycles and decided on the ERay that I’ll use Motul DCTF/Hi-Torque and do a thread on the results with a UOA. DCTF-HT is 100% Ester based synthetic, and the specs are incredible. $13/qt in the 20L/5-gallon containers….enough to do the first two DCT fluid/filter services.

 

The bulletin states "This condition may be caused by an Internal transmission solenoid or switch sticking due to debris" and ends with 2023 model years. This is not proof the problem is caused by a buildup of metallic/clutch material. The debris they refer to is quite likely to be contamination left over from the manufacturing process or self-generated contamination downstream of the filtration system. I agree that particles could make it through the filtration system and congeal to cause clumps of larger particles but there isn't any proof that this is happening or causing the problems.

Yes, debris from the clutch and other mechanical component wear will settle in the sump, this is one of the purposes of the sump. It is normal and happens in every conventional automatic transmission made. It is not proof that the DCT problems are caused by a buildup of metallic/clutch material.

You can't tell by looking at a filter element that it has been loaded beyond its limits anymore than you can tell engine oil is no longer serviceable out by looking at its color. You'd need to do a flow test and see if it is prematurely bypassing. I've seen filters that look horrible but still flow within their limits.

The question I haven't seen answered is if the DCT problems are caused by excessive contamination that can be addressed by frequent filter and fluid changes they why do the vast majority of DCTs maintained per the schedule not have problems? And why have some DCTs failed within 500 miles? And some have failed soon after a DCT service.

 

You’ll looking a long time for proof of anything from a major auto oem. GM also never admitted directly there were widespread problems with the LS7 heads in my C6Z. As the warranty expired I decided to install a set of ported AFR heads. It’s a good thing I did because the valve guides were so ridiculously worn and mis-aligned on the factory heads the valves could have failed at any moment…3 were literally rocking back and forth in the guides. My machinist was amazed they did not fail, yet somehow “vast numbers” of LS7’s were fine. It is still hard to sell a C6Z with original factory heads because of this issue.

Like I said earlier, absence of evidence is not evidence of absence. In this case the evidence is anecdotal. The TR-9080 is a unique single-sump DCT. Some, perhaps many (but not all) TR-9080’s can be prone to debris related issues because of this. Who could guess if their C6Z LS7 was one of failures waiting to happen, similarly, who can guess if their TR-9080 is one of failures waiting to happen…..you can’t. It seems prudent to minimize debris in this DCT, and a yearly fluid/filter service is an easy way to do that.

I agree with your point on filter debris, and drawing any conclusions from the first fluid service is difficult due to break-in wear and manufacturing contamination. Need to get some miles and a couple of fluid/filter cycles on the car before any conclusions can really be made.

 

LOL. Not sure how I did that. i was born in 1954, got my driver's license in 1970. Wish like Hell I was still 33.

 

I ordered the Motul High-Torque DCTF Transmission Fluid 110440. I'll run the HSF on a new filter and then pull an oil sample to send in for analysis.

Aside from additional external filter changes, this will be my main trans service for this year.

 

Has anyone tried (or is going to try) this new C8 DCT filter from Swift Filters:https://cdn.shopify.com/s/files/1/05...f?v=1701898260

 

Looks high quality. I'd give it a try if it was the same price as the factory one but I'd guess it's double that. Trackers will probably like it.

 

I decided to do the same.

UPS delivered a 20L jug on Friday from Ebay……$290 delivered to my door = $13.50/quart. Fresh - dated 2/25, and enough to do the initial change here in the next couple weeks + the yearly service this winter. By the third DCT service @ 7,500 miles, a UOA will have some insights.

 

Why change it so often, are you tracking your car?

 

No tracking.

Any new vehicle I purchase gets its first oil change @ 500 miles and transmission fluid/filter + diffs (if any) @ 5k miles to clear initial break in and mfg debris.

Same for C8, except the first DCT service is @ 2,500. DCT service again this winter, so the 7,500 mile DCT service will be the third, then yearly (typically 3k miles) after that.

If UOA’s look good I might be persuaded to do DCT service every other year.

 

Wondering what you've done to get C8 products to list on Motul's website. I can't seem to get the car to pull up anywhere.


I did my last 2 (15,000 & 18,500 miles) DCT fluid change this winter and will continue to change yearly with my track mileage. I was going to switch to the Valvoline next time... but this is also interesting.

 

And the 2.5, 7.5, then yearly/ 3k DCT service is filter, fluid and the flush routine? Do you do the same amount of service for the other maintenance items like engine oil and filter, brake fluid, lift fluid and coolant?

 

Yes - the shared sump TR-9080 DCT in any C8 I own will have filter/fluid/flush done yearly. I’m doing the front drive motor fluid service on the ERay this winter…..uses Dexron ULV….and then again next year, and following GM recommended interval after that.

My C3-C8 Corvette’s, Lotus, Ferrari, and McLaren get yearly engine oil changes. After enough cars, the mileage just does not accrue on any particular one. Brake fluid and coolant on any car is changed every 3-4 years. All of my cars with the exception of the ERay and 720S are manual transmissions, and they get serviced every 5-years…...or sooner if I notice anything amiss like syncro nibble, etc. The 512TR shears trans fluid for some reason, so that car is every other year trans service. ANY car I buy used starts off with all fluids changed.

The Graziano 7-speed DCT in my McLaren 720S will also get filter/fluid yearly. It is a “normal” split-sump DCT, but it is 900+whp (200 over stock), so not taking any chances.