I have a 2017 Grand Sport M7 and only fluid that's been changed is the oil (2-3x a year). I cant remember if anything else was done on my 1st Chevy service appointment. Car has 9K miles and has seen 3 or 4 tracks days. I am about to get an A&A and wanted to do a full fluid change. Although I dont track the car a ton, I do want stuff that can handle the track/daily driving better than OEM. So what are your recommendations for:
Transmission
Brakes
Clutch
Diff

Thanks everyone!

 

Since you will occasionally track your GS, note that your owner’s manual directs you to change your engine oil twice for every track event. Change your oil to 15W50 before the track day, and back to Dexos2 0W40 after the track. Remember to reset your Oil Life Monitor each time.

Another track related fluid is brake fluid which suffers from high-temperature abuse on the track. Just do a full brake bleed using any DOT 4 fluid before tracking and change back to DOT 3 after your competitive event. The difference between the two is that DOT 4 has a higher boiling point and is very hygroscopic (sucks moisture from the air) so don’t use it for street driving. I use Prestone for both because it’s available everywhere. GM specifically doesn’t want you to use DOT 5, so resist that urge.

Your rear-end differential fluid SHOULD have been changed after the very first track event and then after every 24 hours of track time. You are smart to replace your diff fluid ASAP and be sure to check for metal shavings. I use GM Dexron LS gear oil #88862624.

For manual transmission fluid, there are several options and many people are loyal to certain brands. Probably the most popular brand is Redline D4 ATF. That’s what I use. As an alternate, GM manual trans fluid #88861800 will work. Note that both are automatic transmission fluids and that IS correct.

Clutch fluid takes a beating even with daily street driving due to temperatures. To know when to change, I go completely by color. When it gets a bit dark, I change it. I change all fluids myself and it’s a huge job to change it using the fitting inside the transmission tunnel (also expensive $ if done by your dealer). Therefore, I use a modified Ranger method. Search on this forum for modified Ranger method for DIY how to. As for fluid, I use Prestone DOT 4.

Other considerations for tracking—different alignment specs (check your owner’s manual). Don’t forget to add your brake cooling rings per the owner’s manual and remove your front license plate to improve cooling. Whew!!

Congrats on your new toy and save the wave!
Kangarew

 

Dexos2 0W40 is track ready for your GS; no need to switch to 15W50 per the Owner's Manual

https://www.corvetteforum.com/forums...dexos-2-a.html

 

GM has said differently with some warranty claims--some are even posted on this forum...

 

Yup, that's what I switched to about 2 years ago so I didn't have to switch back and forth

 

So using an RBF fluid for the brakes is a bad idea if not tracking? I'm looking for something I can upgrade from OEM even if i dont track it. But if I do, something with a higher boiling point would be good. Was looking at Motul660. Is that bad for daily driving?

 

Be careful with racing brake fluid--the owner's manual says not use any silicone based fluid. However, there are several branded racing type fluids that meet DOT 4 standards. I would say those are OK. I still would not use DOT 4 fluid for long-term street driving because it's so hydroscopic.

 

My car is 99% track usage. Advanced run group and Time Trials. Instructor. ~12 track days/year. Toyo RR tires. Carbotech XP20 (F) and XP12 (R) pads

Brake Fluid - Castrol SRF. I bleed it every 6 months but it's not unusual for guys to run it for a year. I ran Motul 600 in the past and it was fine but needed bleeding every 3 months so it ends up not being a lot cheaper.
Oil - Mobil 1 0W-40 I change based on the oil life monitor which is usually every 7-9 months
Transmission (M7) - RedLine D4 ATF. Yes, the manual transmission cars use the D4 ATF. I change it once/year
Rear Diff - RedLine 75W90. Already contains the additive. I change it every 25 hours of track time. At 12 days, that's close to once a year as well

 

Why do you think you need “upgraded” brake fluid for street driving?

 

I have '17 GS M7 as well and track a few times a year in Intermediate group. I switched to 0W-40 and change once a year. For brakes I use Motul 600 RBF and bleed before each event. Use the same fluid for clutch and use Ranger method every other event. Differential gets 75W-90 gear lubricant which gets changed annually and for trans I'm using Red Line D4 ATF.

You didn't mention brake pads, but I use Carbotech 1521 (low dust) on street and switch to Carbotech XP8/XP10 combo for track. Also, brake cooling rings only apply to Z51; GS/Z06 don't use them.

 

Jim - purely out of curiosity, why would the OLM say 0% after 7 months if you only track the car. The mileage wouldnt be that high. Cheers.

 

It's usually down around 25%. OLM isn't so much about mileage, it's really about temp, rpm, and it accounts for calendar time. I'd have to look at data from all my track days, but I'm willing to bet my average rpm is >4500 with peak rpm of 6500 being seen multiple times each lap. Avg oil temps are >260.

 

I don't follow. How are you defining "so hydroscopic"? Many european cars do flushes every 2 years on DOT 4. You should be doing it every couple of years anyways so unless DOT 4 can only be good for a couple of months, why are you worried?

 

I concur with most of what's here except changing good brake fluid back to bad fluid? I really don't understand that since Castrol SRF has one of the highest wet boiling points, I've had it in my car for 5 years flushed yearly and its been great. Expensive but worth it.

Just run 0w40-esp year round. The new manuals say its fine, Tadge says its fine, and a '17 will be out of warranty anyways. I think the car runs cooler with it than the 15w50 too. I usually change it twice a year for convenience which is around 40-50% on the oil life monitor.

I do rear diff, tranny, and clutch fluid once a year with OEM fill but your preferred brand will be fine.

 

I guess maybe we can test it to see if it needs to be changed. If it is cheap fluid you get at WalMart, change it every 6 months for all I care. Assuming labor is free. OTOH, if it is expensive fluid, I may elect to have it tested to see how bad it is after a year. If it is really bad, I will change it every 6 months. If it is good at 2 years, why change it every year? Pisses away money and most important, my time.

 

I guess I am looking for a brake fluid better than OEM that can run the street 90% of the time and 10% of time handle the track. Honestly I'm not trying to change brake fluid multiple times a year, so was looking for something that i could use all year for many years if I didn't track the car. But if I do decide to do an event, i don't need to switch to something else. Hope that makes sense.

 

So it looks so far I'm going with this setup for fluids. Again, that car is street driven 85-90% of the time, and the other 10% is track (1 or 2 events per year).

Transmission = Redline ATF D4
Brakes = Still undecided as I want something better than OEM that can be used primarily for the street but is also better at the track. And if I don't run any track events, lasts a while.
Clutch = Prestone DOT 4
Diff = Seems like OEM is the choice?

And I switched to the Mobil 1 0W40 Dexos 2 a few years ago when it first came out so I didn't have to swap back n forth.

 

The issue with brake fluid is that generally, fluids with higher boiling points (DOT4) tend to absorb moisture from the air quicker than fluids with lower boiling points (DOT3).
I say "generally" because each spec defines minimum boiling points wet and dry. Some fluids barely make it into their spec, some are much better. And very few fluids will tell you their actual boing points after 6 months or a year or two years. So DOT4 that's 3 years old may have a lower boiling point than DOT that was flushed in just last week.
The 2019 Manual specifies DOT4 and the reservoir is marked that way. Our 2017 says DOT3.
As the fluid absorbs moisture, its boiling point gets lower, and the moisture could also cause corrosion of parts in the system.

For several autocross weekends each season and maybe one high speed track day at or before mid-season, I just go with the DOT4 that our dealer likes to use and I have it flushed every Spring. If you are tough on brakes, at least one mid-season flush would be appropriate.
The Manual says to flush brake fluid every 3 years, I'd consider that a bare minimum on a car that isn't tracked.

 

If you are worried about mid season or at the end of the year, can't you test it? I'm curious how well the hand held one works vs the lab one.

 

I track my car occasionally with a couple other C7 friends. They run Motul DOT5.1 with no issues. I just switched my 17 to it today. It will get changed once a year to keep it fresh.