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I don't ever remember a Tremec engineer saying the problems were due to clutch debris.
There was a post on Facebook where a Tremec employee stated that Tremec was having a problem with contaminated parts from suppliers.
Yep I don’t recall that clutch plate wear statement but adding to my speculation of cause:
I felt the somewhat jerky motion when I crawled into my garage at ~2 mph for the 1st ~1000 miles was probably caused by the multi plate 1st gear clutch watering off high spots. That went away after ~1000 miles.
Was my thought possibly why folks in 2020/2021 with early DCT CELs and GM Service telling dealer techs just do a flush. No DCT filter change no new fluid, just a Flush. Most reported CEL gone and did not return
One reason I took advantage of GMs free offer to have DCT filter change with flush prior at year 1 with ~3000 miles
As I recall Porsche DCT (and others) have separate fluid source for the clutches.
Just more speculation BUT FITS!
Could they have improved the clutch material in recent years as:
i did not have Jerky feeling in my 2024 E-Ray initially
Don't see the early CELs where it goes away with Flush!
or the eray uses more of the electric drive at low rpm
Originally Posted by JerryU
Yep I don’t recall that clutch plate wear statement but adding to my speculation of cause:
I felt the somewhat jerky motion when I crawled into my garage at ~2 mph for the 1st ~1000 miles was probably caused by the multi plate 1st gear clutch watering off high spots. That went away after ~1000 miles.
Was my thought possibly why folks in 2020/2021 with early DCT CELs and GM Service telling dealer techs just do a flush. No DCT filter change no new fluid, just a Flush. Most reported CEL gone and did not return
One reason I took advantage of GMs free offer to have DCT filter change with flush prior at year 1 with ~3000 miles
As I recall Porsche DCT (and others) have separate fluid source for the clutches.
Just more speculation BUT FITS!
Could they have improved the clutch material in recent years as:
i did not have Jerky feeling in my 2024 E-Ray initially
Don't see the early CELs where it goes away with Flush!
when taking off that is thus putting less wear on the clutches. have there been any dct failures on erays?
when taking off that is thus putting less wear on the clutches. have there been any dct failures on erays?
If you look at all DCT replacements on the Forum none show failures of clutches, gears, synchro's etc. Since the gears, synchro's are the same in the Z06 higher hp engine as the standard C8 (and E-Ray LT2) doubt it's a gear/clutch etc, issue. If you watch the video by a GM tech who worked on 50 with CELs (my post #19,) appears to me mostly minor issues with solenoid valves or passages clogging or possibly failure of the very many sensors that assure shift forks are in the proper position before one clutch disengages and the other engages. We don't know as Tremec who is the one investigating replaced DCTs has not said. Why should they! Other than the hydraulic actuators and the many sensors, it's similar to the 7 speed Tremec standard transmissions I had in my two C7s and the 6 speed Tremec in my C6! They were rock solid.
PS:Tremec has been known for building very durable standard transmissions for trucks and cars. In 2010 they acquired the high-tech automotive design and development organization HOERBIGER Drivetrain Mechatronics located in Belgium. HOERBIGER products and software solutions are found in leading European sports cars, including Ferrari Italia 485, AMG SLS and McLaren MP4-12C.
The C8 DCT is basically two 4 speed standard transmissions but instead of a manual lever moving the shift folks there are hydraulic actuators computer controlled.
The issue I raised with the 1st gear clutch had to do with possible break-in wear of high spots on the multiplate clutch plates. As I said, after ~1000 miles it was smooth at slow (<4 mph) speeds when it must slip. Unlike some other DCTs that have a separate clutch reservoir section and probably pump, the Tremec system uses the same fluid for all systems. Expect clutch plate wear is higher than any gear, synchro wear. It could clog solenoids, passages etc. Only Tremec knows! When warranty is up (many are now or close) I suspect trans repair folks will find and fix the issues.
If you look at all DCT replacements on the Forum none show failures of clutches, gears, synchro's etc. Since the gears, synchro's are the same in the Z06 higher hp engine as the standard C8 (and E-Ray LT2) doubt it's a gear/clutch etc, issue........
Jerry,
How do you know that? We have already seen, recently, some replacements of clutch components in the field. It's true that there aren't any DTCs that say a shift fork, or clutch, or a gear, or shaft, or a bearing is bad. What we will see is an error in a position sensor, or a pressure sensor, or a temperature sensor, or speed sensor - maybe others. They all require diagnostic procedures to determine the cause and repair it. Some cases are resolved by various remedies including, recently, replacement of clutch components. But others result in transmission replacement. In those cases, as far as I know, we never find out what the actual cause was (so in that sense, you are right, we have no evidence of failure gears, synchros). But there are plenty of codes associated with errors in shifting and shift fork position, pressure errors, temperature errors, speed sensor discrepancy errors, and so on. Those might be a failure in the hydraulic actuators that move those components, or they might be an issue with synchros or gears etc.that prevents proper motion. I think you are probably correct - its more likely the actuators - but that's just speculation on my part. I don't see how we actually know.
I meant that the electric drive causes less friction material to be lost when launch
Originally Posted by JerryU
If you look at all DCT replacements on the Forum none show failures of clutches, gears, synchro's etc. Since the gears, synchro's are the same in the Z06 higher hp engine as the standard C8 (and E-Ray LT2) doubt it's a gear/clutch etc, issue. If you watch the video by a GM tech who worked on 50 with CELs (my post #19,) appears to me mostly minor issues with solenoid valves or passages clogging or possibly failure of the very many sensors that assure shift forks are in the proper position before one clutch disengages and the other engages. We don't know as Tremec who is the one investigating replaced DCTs has not said. Why should they! Other than the hydraulic actuators and the many sensors, it's similar to the 7 speed Tremec standard transmissions I had in my two C7s and the 6 speed Tremec in my C6! They were rock solid.
PS:Tremec has been known for building very durable standard transmissions for trucks and cars. In 2010 they acquired the high-tech automotive design and development organization HOERBIGER Drivetrain Mechatronics located in Belgium. HOERBIGER products and software solutions are found in leading European sports cars, including Ferrari Italia 485, AMG SLS and McLaren MP4-12C.
The C8 DCT is basically two 4 speed standard transmissions but instead of a manual lever moving the shift folks there are hydraulic actuators computer controlled.
The issue I raised with the 1st gear clutch had to do with possible break-in wear of high spots on the multiplate clutch plates. As I said, after ~1000 miles it was smooth at slow (<4 mph) speeds when it must slip. Unlike some other DCTs that have a separate clutch reservoir section and probably pump, the Tremec system uses the same fluid for all systems. Expect clutch plate wear is higher than any gear, synchro wear. It could clog solenoids, passages etc. Only Tremec knows! When warranty is up (many are now or close) I suspect trans repair folks will find and fix the issues.
Since the clutch engagement can be programmed differently
Jerry,
How do you know that? We have already seen, recently, some replacements of clutch components in the field. It's true that there aren't any DTCs that say a shift fork, or clutch, or a gear, or shaft, or a bearing is bad. What we will see is an error in a position sensor, or a pressure sensor, or a temperature sensor, or speed sensor - maybe others. They all require diagnostic procedures to determine the cause and repair it. Some cases are resolved by various remedies including, recently, replacement of clutch components. But others result in transmission replacement. In those cases, as far as I know, we never find out what the actual cause was (so in that sense, you are right, we have no evidence of failure gears, synchros). But there are plenty of codes associated with errors in shifting and shift fork position, pressure errors, temperature errors, speed sensor discrepancy errors, and so on. Those might be a failure in the hydraulic actuators that move those components, or they might be an issue with synchros or gears etc.that prevents proper motion. I think you are probably correct - its more likely the actuators - but that's just speculation on my part. I don't see how we actually know.
Yep should not have used the definitive word none! But with >100,000 C8's out and probably a statistically significant percentage represented by the form(s) is why I said what I did. And as I added, only Tremec knows and why should they say. Surely not to make forum members happy! As typical, even if it were all presented the reaction by some would still be disbelief!
I don't know ZF (who makes the Porsche DCT) or Magna (who make Ferrari DCT) failure rate. Since Tremec is newer at the game expect it's higher. But some who have experienced no issue also express apprehension.
When my friend who built the TH400 in my Street Rod and was focused on transmission repair (when he built mine his business was called Custom Transmissions) starts repairing I'll ask! He was repairing automatic transmissions for the Chevy, Caddy, Ford etc dealers. As he told be the incidence on new cars was sufficiently low they could not keep a transmission trained Tech on the payroll. It's now a more automotive repair name as his 6+ servcie bays are filled with a cross section of of repair issues. His tech's just repaired my friends GM Truck trans where he had a torque converter failure (common for some year GM trucks.)
So how many DCT's have failed? 1%,2%, More than 5%. How many are service ? How many have never failed?
No one outside of GM and Tremec know the answer to those questions. That doesn't, of course, stop people from speculating or even touting the results of unscientific internet "surveys" to claim they know the answer.
There are also people, including at least one person who seems to be very familiar with the internal of the transmission (no, I don't remember who or where he posted it) who believe that many of the failures have nothing to do with the fluid, but are the result of unrealistically tight tolerance windows on many of the (literally) dozens of sensors in the DCT, which trigger failure modes even when nothing is really wrong. In support of this theory, the one person I actually know who had a transmission issue said the car seemed to drive just fine even after the DIC told him to park the car.
GM's service procedures / warnings on the filter service would seem to indicate that fluid contamination is the cause of some failures, but it might not be the only cause,
Originally Posted by jim2527
5 years ago I posted that a Tremec engineer said it was from clutch debris. Are the current problems still from clutch debris? IDK.
Or to be precise, someone who claimed to be a Tremec engineer. As I recall, he offered no proof of his employment.
Last edited by Red Mist Rulz; Jan 21, 2025 at 04:51 PM.
The only person I know personally who had a DCT failure had it happen on his way home from museum delivery, with about 400 miles on the car. I doubt that was because the car didn't get driven enough....
Yikes ... am slated to do just that in March ... what year car and what was the issue? Stranded or ... inquiring mind here!
If you start listening to all the horror stories on here you'll end up cancelling the order. don't listen...
Typical Corvette owner who refuses to admit the Corvette has problems.
I have first hand experience with transmission problems on my C8 and know of six other C8 owners who have had to have their transmissions repaired or replaced.
This person has gone through the buy back process on two C8s because of transmission issues. The first C8 the transmission went out after two days of ownership. He at least got two months and 3000 miles out of the second C8 before its transmission decided to take a crap. He finally said enough is enough and bought a Supra.
Don’t kid yourself, there are reliability issues with the DCT in the C8 Corvette that GM has failed to address after 5 model years other than sending owners a letter telling them to replace the filter at 7500 miles and fluid at 3 years.
I agree with you 100%. I had one of the 1st 2020 Z51 Coupes and as soon as I hit 1500 miles drove it hard at least 3x a week put on 23000 miles in 2 years not one issue at all. Then got and Aston Martin DB11 for 6 months and then bought a 2023 HTC Z51 now has 15000 miles on it knock wood again not one issue. I manually downshift at corners and light. And occasionally manual upshift as well. On the 2020 Coupe performed many 0-60 runs avg at 2.6 sec and 3 times 2.5 its was definitely faster than my Convertible. The car was made to be driven hard which is why warranty covers track use and 0-60 launches.
Drive it like you stole it and enjoy
I treated mt c8 like a motorcycle with a wet clutch. Changed filter multiple times. Here is what I seen. Took filter apart each time.
400 miles,easy break in/driving- filter stuffed with particles ,pretty bad
1100 miles, a lot of material in filter- better but not great
2600 miles- cleaner but still dirty
5500 miles, very little debri,pretty clean
6600 miles- very clean
So, My opinion is the clutch material clogs the filter and hurts the valve body. My car was procharged at 2500 miles. It's run pretty hard and shifts very good with no issues.
I treated mt c8 like a motorcycle with a wet clutch. Changed filter multiple times. Here is what I seen. Took filter apart each time.
400 miles,easy break in/driving- filter stuffed with particles ,pretty bad
1100 miles, a lot of material in filter- better but not great
2600 miles- cleaner but still dirty
5500 miles, very little debri,pretty clean
6600 miles- very clean
So, My opinion is the clutch material clogs the filter and hurts the valve body. My car was procharged at 2500 miles. It's run pretty hard and shifts very good with no issues.
In order to get past the filter, if that is what is happening, the clogged filter would need to go into bypass mode, allowing the debris to get into the lines and valves, right?
GM and or Tremec likely performed analysis similar to what you did, dissecting the filters at various mileages to see the filter loading. The fact that continued to accumulate all the way to 5500-6600 miles would explain GM's statement about a "7500 mile break-in period" for the transmission (that appears in the later manuals), and would also explain GMs insistence that the filter be changed between 7000-8000 miles, even if done earlier. After which the next change is 22,500 miles, so 15000 more, then every 22,500 miles after. So once the heavy break-in shedding is complete, the intervals can be progressively longer.
The fact that the filter is dirty does not, by itself, prove that it went into by-pass mode. There have been photos that show some debris on the filter housing lid - which could have been from filter bypass, or not. I wonder what the filter would look at the second scheduled change at 22,500 (after 15000 miles) and the third scheduled change at 22,500 miles. If it is going into bypass in the first 7,500 miles, its a mystery as to why GM did not detect that during their analysis and testing. If the theory is correct, maybe its because some cars are outliers and shed more debris than expected in the 7500 mile period.
In order to get past the filter, if that is what is happening, the clogged filter would need to go into bypass mode, allowing the debris to get into the lines and valves, right?
GM and or Tremec likely performed analysis similar to what you did, dissecting the filters at various mileages to see the filter loading. The fact that continued to accumulate all the way to 5500-6600 miles would explain GM's statement about a "7500 mile break-in period" for the transmission (that appears in the later manuals), and would also explain GMs insistence that the filter be changed between 7000-8000 miles, even if done earlier. After which the next change is 22,500 miles, so 15000 more, then every 22,500 miles after. So once the heavy break-in shedding is complete, the intervals can be progressively longer.
The fact that the filter is dirty does not, by itself, prove that it went into by-pass mode. There have been photos that show some debris on the filter housing lid - which could have been from filter bypass, or not. I wonder what the filter would look at the second scheduled change at 22,500 (after 15000 miles) and the third scheduled change at 22,500 miles. If it is going into bypass in the first 7,500 miles, its a mystery as to why GM did not detect that during their analysis and testing. If the theory is correct, maybe its because some cars are outliers and shed more debris than expected in the 7500 mile period.
Concur. I do recall a post from someone that knows a Tremec engineer that said the filter was undersized. I have no idea if this is fact the case. But if the filter is close to the margin on capacity in early DCT life, it could explain why some DCTs have issues and some don't. I suspect there's a distribution (bell curve) of debris generation DCT to DCT, driving style and tolerance of all the parts and pieces in the DCT which could, if on the wrong side of the curve get you in trouble so to speak. This assumes that any contamination comes from the clutches and not left over machining debris left inside during the manufacturing process (Toyota and Hyundai learned this lesson the hard way with 1000's of engine replacements. I for one). I really do think changing the filter early and perhaps often in the first perhaps 10K miles will give you the best chance of at least eliminating the filter loading as an issue. Since I track my car I change my filter (and fluid) a lot more often than the daily driver. It would be refreshing if someone would open the lid on failure investigation results if in fact removed DCTs actually get torn apart and analyzed.
