Transmission Filter Change
Burning Brakes
Joined: Nov 2022
Posts: 1,048
Likes: 1,108
From: Western Mass
Debris collects in the valve body solenoids where it stays until it is flushed out. Even if the filter were to never again go into bypass, the debris collects and stays in the valve body until flushed. And the problem with this is a solenoid malfunction might result in two gears being engaged at the same time. When this happens, the transmission immediately destroys itself. This is why the DCT sometimes drops either odd or even gears when it detects an internal pressure fault. This is the control system's way of protecting the DCT. Sometimes it saves the unit, sometimes it does not. Most of the time, GM wants the valve body changed because the cost for this is much lower than changing the unit. If the unit suffered no internal damage, a new valve body might fix it.
The best way to circumvent DCT problems is to regularly change the filter. Best possible course of preventive maintenance action would be to periodically run the flush procedure on a new filter and then replace that filter with a new one.
The best way to circumvent DCT problems is to regularly change the filter. Best possible course of preventive maintenance action would be to periodically run the flush procedure on a new filter and then replace that filter with a new one.
I'd also like to understand where the info is on the filter going into bypass at cold start. Seems like a really dumb design.
Race Director
Joined: Mar 2007
Posts: 11,278
Likes: 8,412
As has been stated many times before, the DCT filter is severely undersized. Because of this, on every cold start when the fluid is cold, the filter bypasses until it warms up. This is why the trans fluid must be above 140 degrees to run the HSF procedure. GM won't tell you this and a few other things about their DCT. What owners should be thinking about is the cost of a replacement transmission when the car is out of warranty and how long will it take to get a replacement unit?
Race Director
Joined: Mar 2007
Posts: 11,278
Likes: 8,412
I don't disagree with this approach. I'm hoping I can get my local dealer to run just a HSF at which point I'd take it home and change the filter. The only curiosity I have with your recommendation is why would you recommend a new filter, then flush then new? I plan on changing my DCT filter a lot more often than what GM recommends sans the HSF if I can't get them to do it (hoping we get a scan tool that can do it eventually). I changed my fluid and DCT filter at 2450 miles and put in the extra 2 liters (track use) and will replace again at 7500 miles (at the dealer). Then at every oil change (5000 miles). It's only $100 and my time.
I'd also like to understand where the info is on the filter going into bypass at cold start. Seems like a really dumb design.
I'd also like to understand where the info is on the filter going into bypass at cold start. Seems like a really dumb design.
https://www.corvetteblogger.com/2023...e-c8-corvette/
Last edited by Andybump; Feb 18, 2024 at 09:16 AM.
Burning Brakes
Joined: Nov 2022
Posts: 1,048
Likes: 1,108
From: Western Mass
Andy, agree 100% for a filter that is beyond the recommended interval. But see no need if doing earlier than the manual requires. If that were the case then the filter is tremendously undersized
Drifting
Joined: Feb 2023
Posts: 1,353
Likes: 1,115
Race Director
Joined: Aug 2016
Posts: 12,721
Likes: 10,149
From: Garden Valley CA
As has been stated many times before, the DCT filter is severely undersized. Because of this, on every cold start when the fluid is cold, the filter bypasses until it warms up. This is why the trans fluid must be above 140 degrees to run the HSF procedure. GM won't tell you this and a few other things about their DCT. What owners should be thinking about is the cost of a replacement transmission when the car is out of warranty and how long will it take to get a replacement unit?
Drifting
Joined: Feb 2023
Posts: 1,353
Likes: 1,115
Hi. I know you have have stated before that the filter is too small. I have no basis to challenge that. In fact, I have noted before that the Maserati MC20, which uses the exact same Tremec 8 speed transmission, calls for replacement of that filter once year or every 9320 miles. It never goes to a longer mileage interval. Not proof that the filter is too small, but it is proof that another manufacturer thinks more frequent replacement is necessary. But I don't recall seeing the statement about the filter going into by pass when it is cold. Is that your theory, or is there some evidence of that happening (other than the fact the GM calls for the HSF every time, without an explanation for why that is necessary)?
What is of greater concern is the lack of any forthright information about the GM Tremec DCT with regard to what is being done, if anything, to fix the durability and reliability of this transmission. On the face of it, if you rely only on published data you hear from both, nothing is really wrong.
Drifting
Joined: Feb 2023
Posts: 1,353
Likes: 1,115
I've only seen it stated by a few people on the forum that the DCT filter is undersized and I've never seen it backed up by any data. If the DCT filter is severely undersized why is it that the majority of C8s don't have DCT problems? If DCT problems are because the filter is severely undersized then a majority of DCTs should be having problems unless somehow their filters aren't undersized.
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