Maxie2U

Why are you changing the differential fluid and transmission fluids with such low mileage? GM recommends changing the rear axle fluid at 45,000 mile and the transmission fluid @ well actually the manual does not even show a required fluid change.

Kracka

GM's transmission fluid isn't anything special so a new high-quality fluid makes the transmission shift MUCH smoother. Changing out the rear differential fluid early is never a bad idea since it removes all the initial break-in materials and shavings. The factory-fill fluid is typically the only time you'll see the silver metallic sheen in the drained gear oil.

LT4CMG

Was going to say it Maxie, but the OP just said it for me. Believe me, with high performance cars you drive hard, you will not regret it. Btw, is that a new c7 in your avatar pic or the one you’ve had?

I have the trans fluid, full synthetic, waiting for spring, before I bring it out. Damn M7 is awesome, but notchy in this thing. Same with my M6 Camaro. Changed the fluid from the factory crap and that TR6060 became amazing and silky smooth

Maxie2U

I wonder if this applies to the auto transmission too?

Poor-sha

Owners manual says to change the diff fluid after the first track day.

Kracka

It does, but changing out the automatic transmission fluid isn't quite as easy of a DIY job so you may want to let the dealer or shop tackle it. My suggestion would be Redline D6 ATF for a high-quality full-synthetic fluid. For this, I would suggest change intervals of every 30-45k miles (so not as frequently as manual transmission fluid).

Kamran

Most of what you see coming out in diff fluid I believe is carbon fiber particles from the clutch wearing in. It's kind of thick and sticky.
I've got 7,000 miles and just changed to 4th diff fluid with mostly track use. Also on 3rd tranny fluid. GM recommends to change diff fluid after every 20 track hours. I like to keep the fluids in new condition and send samples out frequently for testing to feel confident to hammer away.

Much easier to change it and sleep well than argue over conviencing myself that I don't need to do it.

All bets are off if it is a waxer or garage Jewelry.

Kracka

Factory lifetime fill fluid

Maxie2U

Avatar is a pic of my 2016 the day I picked it up back in Oct '15.

64drvr

Thanks for posting this DIY. J just flushed the rear diff on my z06 with this. I used about 2.999 quarts of the mentioned 75w90 GM oil and the Plews pump on Amazon. I was able to reach the fill plug without a flex head ratchet by utilizing 3.500" of extension; this facilitated using a torque wrench to finish the process.

Maxie2U

My question is; if I used Redline D4 and then had a transmission failure would GM still warranty the transmission or void the warranty?

Kracka

It's a major petroleum company's fluid that meets Dexron III spec, I see no reason why they wouldn't honor the warranty.

muncie21

Now that my friends is a very precise extension. I'm lucky to have more than 1 decimal of precision

FYREANT

Phudu2004

Thanks for the DIY. I want to to ask a couple questions regarding the use of Mobil 1. Went to AutoZone today trying to buy the transmission oil from Mobil 1 but it said for automatic transmission only. I have a 2015 C7Z manual. So, is it ok to use that?

Second, I saw they have Mobil 1 75-90 but, online I saw some posts said that Mobil1 gear oil 75-90 would need the friction modifier added to it. Is that true?

I’d have gone with Redline but couldn’t find any around. And I’ve been using Mobil1 on all my cars. But they’re not a Corvette so, I can take chances on them.

FYREANT

Order the Redline fluid online. Amazon prime!

Pineapple

Thanks for DIY, I just did the tranny and diff fluid yesterday. For the tranny fill/drain plugs, they have some sort of orange seal on the threads, much like how you wrap Teflon tape around the threads on pipe fittings. Are these plugs ok to reuse as is with NO reapplication of the orange seal?

The manual shows the tranny as having a 100k mile service interval, pretty much a sealed unit. Maybe that’s why they used those type of plugs?

FYREANT

Yes you can reuse. I did with no adverse effects.

Kracka

Walmart.com has free 2-day shipping as well, this is where I got my most recent jug of Redline ATF D4.
Agreed. I've reused mine twice now without adding any additional thread sealant and am experiencing no leaks of any sort.

Kracka

This is the correct Mobil 1 gear oil for the rear differential: https://mobiloil.com/en/gear-lubrica...c-gear-lube-ls
It already contains the friction modifier, but additional additive might be needed in certain applications.

Here is the correct Mobil 1 ATF for the M7 manual transmission: https://mobiloil.com/en/automatic-tr.../synthetic-atf