Sep 9, 2019
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Hey Folks,

Was just checking out some things from Spring Mountain from some folks who were driving the C8s there...some info I saw was Trans fluids need to be changed ever 7500 Miles or 12000km for us Canucks. Engine break-in is 800 km and if your gonna track or do some burnouts 2400km recommendations from GM. To check oil the engine will have to be running and will have to be brought to Temp. When on a hill car will automatically go into a parking break mode.

If your tracking the car you need to put in 1.8 l of Pentosen FFL fluis then you leave that in after tracking it.

Just some stuff I learned today.

Cheers,

Kevin
 
Hmm, the transmission change interval is interesting.

The new transmission must punish it’s fluid pretty badly for such a low interval (compared to previous designs for autos and manuals).

Doesn’t mean it’s a bad design, just that it’s hard on the fluid.

Would be interesting to see a maintenace manual for it to understand it’s construction a bit more.

I suppose it could also be a reflection of spec-ing a lower viscosity fluid for fuel consumption and parasitic loss considerations. That usually means more frequent change intervals and sometimes, less....”robust”.....protection from the fluid.
 
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I imagine the dual-clutch system has a lot to do with this. The clutches are in the transmission now, bathed in the transmission fluid. There's a lot more going on in there than the old-fashioned manual or automatic transmission.
 
I imagine the dual-clutch system has a lot to do with this. The clutches are in the transmission now, bathed in the transmission fluid. There's a lot more going on in there than the old-fashioned manual or automatic transmission.
Umm, not to be contrary, but "old fashioned" automatics have clutches and pressure plates also running in the fluid. Lock up on torque convertors are the same deal: friction disc running on a pressure plate in the torque convertor and running in trans fluid. Smaller diameter than a manual, but there's multiple clutches, so same (if not more) friction material to beat up the fluid. They deal with slippage and heat just like any other "wet clutch" system.

It's also easy to make a manual shift automatic though both mechanical and electronic means. manual valve body or if the trns is electronic; it's a simple coding change. My 2016 f-150 is a 6 peed auto that I can shift like a standard any time I want with the flick of a switch. They typically run out to the 100K mark before OEMs recommend fluid/filter change. And in my truck, good luck punishing the fluid harder in a C8 than my auto does when I'm pulling a 9,000-10,000 lb trailer.

A manual shift automatic is not exactly "new" technology....even if GM is touting it as so and using a little different scheme from what's been used so far.

Biggest difference I see in their ad hype is the speed at which it will "manual shift". Of course, that it's rear mounted and a "transaxle" is also different from what could be considered an "old fashioned" automatic.

I'm going to wager the heat management scheme isn't shedding the heat as quickly as they had hoped. That's a reasonable assumption given the fact the entire drivetrain is buried in the rear of the body. if you want to drastically shorten the life of automatic trans fluid; overheat it or run it hard and hot for a prolonged time.

With "rear everything" in a C8, all the cooling has to be done by trying to route air in to the bay or getting the fluid out of the bay to a cooler of some sort. Getting the fluid out to a cooler is actually a great cooling scheme as anytime you can get it out of the component for a longer time will bean more temp delta. It also means the system can hold more fluid, which also helps with cooling. Combine the rear mounting with the usual "fuel saving" fluids (IE: thin) they use these days, and it likely ads up to a decreased life expectancy for the fluid.

Of course, that's all just speculation on my part. But it's based on roughly 40 years of automotive/engineering experienceand understanding how this stuff work on the "micro" level. That's 40 years of working on them, not just owning/driving/admiring them.......;)
 
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I understand your background and understanding of how automatic and manual transmissions work, but an automatic and dual-clutch are not the same thing by any stretch of the imagination. Yes, you can control the shifting of an automatic with the help of electrical controls and goodies, but, to my understanding, the primary component in them is the torque converter, which uses hydraulic pressure to allow the transmission to 'slip' while changing gears. Yes, it produces a crazy amount of heat, but it doesn't work the same as a dual-clutch.

A dual-clutch transmission is exactly that: Two clutches, just like the dry clutch used in your manual transmission. One clutch - consisting of multiple friction plates - is connected to the odd gears, 1-3-5-7 and another is connected to the even gears 2-4-6. As you shift, it disengages the engaged clutch and engages the other clutch, while shifting the mechanical components similarly to how you shift your manual transmission.

Why I suggest this is the reason for more frequent oil changes is the debris that will be released from the clutch pad material as it shifts hard between each gear, not from excessive heat.


My $0.02.
 
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I understand your background and understanding of how automatic and manual transmissions work, but an automatic and dual-clutch are not the same thing by any stretch of the imagination. Yes, you can control the shifting of an automatic with the help of electrical controls and goodies, but, to my understanding, the primary component in them is the torque converter, which uses hydraulic pressure to allow the transmission to 'slip' while changing gears. Yes, it produces a crazy amount of heat, but it doesn't work the same as a dual-clutch.

A dual-clutch transmission is exactly that: Two clutches, just like the dry clutch used in your manual transmission. One clutch - consisting of multiple friction plates - is connected to the odd gears, 1-3-5-7 and another is connected to the even gears 2-4-6. As you shift, it disengages the engaged clutch and engages the other clutch, while shifting the mechanical components similarly to how you shift your manual transmission.

Why I suggest this is the reason for more frequent oil changes is the debris that will be released from the clutch pad material as it shifts hard between each gear, not from excessive heat.


My $0.02.
Nah, your dual clutch is doing the same thing the "old fashioned" automatic is doing: it applies and disengages all those clutch packs on every shift. Toss in that it also has engagement "bands" that are also friction material lined and there's"boat loads" of friction material contamination running around in a "traditional" automatic. Have a look at an "old" TH400 cutaway:

attachment.php


Everywhere you see those brown/beige colored discs is a clutch with friction material. Lots and lots of them in there. And that doens't even take into account the bands which also have friction material that contaminates the fluid. As well, newer auto's with lock up convetors have even more friction material running int he trans fluid.

The torque convertor is just a viscous coupling that multiplies the torque from the engine and keys into the trans body to run the hydraulic pump (which supplies fluid pressure for clutch pack operations). If you've ever seen the "two fan" demonstration/example, you'll understand how the torque convertor works. in a nutshell; the engine spins one fan and the air it drives turns the other fan. Torque convertor does the same thing, it just uses fluid instead of air like a fan would. Split open a torque convertor and you are actually going to see turbines, which are a type of fan:

Torque-Convert.jpg


To be technical, it's actually termed "rotor" and "stator". One is attached to the torque convertor body and is spun by the engine, the other is connected to the transmission input shaft and is spun by the fluid driven by the engine side. That's it in a nutshell, except modern TC have clutches in them to lock up the convertor for better MPG in steady state highway type operations.

You can sit at idle with the brakes on because of that viscous coupling, but as soon as it's moving, the clutch packs and bands do all the heavy work. The clutch packs are what engages/disengages every time the car shifts, not the torque convertor. The clutches ride in the fluid, but they also use fluid pressure to schedule the shifting. It's all hydraulic in "traditional" auto's. Electronic auto's still use the fluid to shift, it's just through electric solenoids instead of just springs, balls, valving and passages/ports.

All "old fashioned" automatics contaminate the oil with the clutch friction material. It's why they have a massive filter in the bottom of the pan. Overheat them and they absolutely pollute the oil with friction material, along with glazing the clutches and bands. They still run out to 100k before needing a change. But overheat the fluid ONCE and it's DONE. Change it or expect transmission damage shortly thereafter. Or at the very least, significantly reduced transmission life expectancy. The sucky thing about transmission fluid and overheating is that most vehicles don't have a temp guage or even an idiot light. You can fry your trans fluid and not even know it. That's why my F-150 has an otpion on the electronic cluster to swap the boost guage for a transmission temp gauge. the temp guage is up all the time on mine. I could care less how much boost it's making as I have no control over that other than my right foot and it's going to "bypass" at a predetermined pressure anyways. Nope, I'd rather know if that trans fluid is toasted or not...:)

Nah, I'm sticking with "heat" being the biggest concern for fluid life and why the interval seems so low to me.

But, I've also been wrong before so it wouldnt be the first time....LOL!
 
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Thanks for the clarification.

I'm by no means an expert in this stuff, but I'm open-minded and love to learn. My background is mechanical engineering and design. I'm genuinely interested in this stuff and understand it.

I'm curious if the 12,000km transmission fluid change is a part of the break-in, as in it only needs to be done once. No modren vehicle requires frequent transmission fluid changes, so why would this?

I'm going to Google Porsche's DCT manual and see what it says.

I know you should flush your transmission fluid after 24 hours of driving on the track.
 
...I'm curious if the 12,000km transmission fluid change is a part of the break-in, as in it only needs to be done once...

That would be a reasonable assumption and would make sense. 12,000 kms for a change seems really low. there's some people that could go through 2-3 trans oil changes a season at that rate. that just seems excessive to me, so a "break in" change makes sense.

But without more specific info from GM, it's all just guessing.....;)

I know you should flush your transmission fluid after 24 hours of driving on the track.

Yep, because that puts a beatin' on the oils harder than the "severe service" maintenance schedule ever conceived of. Racing puts machinery in a whole different world of hurt compared to regular driving use. But don't underestimate how hard daily driving is on a car. Most "daily driving" tasks actually fall under the "severe service" schedules....racing it is just a hyper-level of "severe".

:)
 
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That would be a reasonable assumption and would make sense. 12,000 kms for a change seems really low. there's some people that could go through 2-3 trans oil changes a season at that rate. that just seems excessive to me, so a "break in" change makes sense.

But without more specific info from GM, it's all just guessing.....;)


Just like everything going around the internet these days: It's all speculation.
 
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This info is right from the US vette sales people that were just at Spring Mountain that were invited by Chevrolet. This info was given to them by the Chevrolet people last week.

I'll find and post the VLOGS.

Cheers

Kevin


Not to discredit the vlogs and salespeople, but I take everything with a grain of salt, unless I see it in writing, and is coming directly from GM or a credible source that is citing GM.
 
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This is right from GM...they are only allowed to release so much info.There is a hush date for them before they can release the vids they took in class and on the track. This was a GM Corprate run invite....once I get to my laptop I'll post the videos:canada:

I understand it was a GM thing (I wish they invited us Canadians as well), but it came from GM, to the salespeople, to videos recorded by said salespeople. There are likely some details missing, such as whether or not this is a regular interval oil change or a one-time thing. I want to get my hands on an owner's manual or something so I can get it straight from the horse's mouth.
 
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