Overfill your Differential
Thread Starter
Burning Brakes
Joined: Sep 2008
Posts: 810
Likes: 58
From: Alva Florida
Overfill your Differential
I just purchased a 2016 Stingray base model with 52000 miles.
Changed the differential fluid, emptied and refilled with GM Correct Fluid.
I drained and filled with 3 quarts of fluid, and it still took more (maybe a quarter of a quart).
Checked the amount that came out of the Diff (refilled the used containers) and it was a hair over 2 quarts of fluid.
Should I be concerned about overfilling and drain some out? I thought you filled a differential till fluid trickled from the fill plug...
Thanks.
Changed the differential fluid, emptied and refilled with GM Correct Fluid.
I drained and filled with 3 quarts of fluid, and it still took more (maybe a quarter of a quart).
Checked the amount that came out of the Diff (refilled the used containers) and it was a hair over 2 quarts of fluid.
Should I be concerned about overfilling and drain some out? I thought you filled a differential till fluid trickled from the fill plug...
Thanks.
Race Director
Joined: Sep 2000
Posts: 11,143
Likes: 1,913
From: Missouri City, TX
Intermediate
Joined: Sep 2014
Posts: 36
Likes: 7
From: Western PA
As I recall, the Z06 has a differential cooler which must also be filled. The shop manual advises filling the diff, then running the drive train with the rear wheels off the ground to circulate the lube to refill the cooler. Then top-off the diff again to complete the refill.
I usually take a short drive instead of running with rear wheels off ground.
I usually take a short drive instead of running with rear wheels off ground.
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Drifting
Joined: Jun 2013
Posts: 1,428
Likes: 478
From: Maryland, USA
as long as it relatively level not talking has to be exact and it starts dripping out some, plug it back up and good to go. as mentioned they were known to underfill for sure.
i did mine after a nice drive to get it all warm up.
i did mine after a nice drive to get it all warm up.
Race Director
Joined: Mar 2001
Posts: 19,965
Likes: 6,770
From: Bonneville Salt Flats
There was a big todo back in the day when these first came out; it was that the diffs where not completely filled from the factory. Indeed, I watched a vid of the CEO of the the diff manufacturer explaining that they were all shipped with the correct amount no matter how they "tested" upon install.
It was common for a new C7 to be underfilled according to the standard GM fill measure (to the bottom of the check/fill hole). Indeed, when I first checked my then new 2018 it was 9-fl.oz. low by the GM checking method. So, I filled to the correct level. All of which was common practice back then. As long as not filled beyond the check-point (it would just run out in the process of trying to check and screw-in the plug) it just give a little extra capacity if the CEO was honest. All the best.
It was common for a new C7 to be underfilled according to the standard GM fill measure (to the bottom of the check/fill hole). Indeed, when I first checked my then new 2018 it was 9-fl.oz. low by the GM checking method. So, I filled to the correct level. All of which was common practice back then. As long as not filled beyond the check-point (it would just run out in the process of trying to check and screw-in the plug) it just give a little extra capacity if the CEO was honest. All the best.
Melting Slicks
Joined: Feb 2018
Posts: 2,184
Likes: 1,049
From: North Texas
Kind of tough to overfill since the fluid will drain out the fill port almost as fast as you put it in.
Under fill, easy to do.
Car level, fill till it drains out the fill port, when down to a drip install the fill plug.
Under fill, easy to do.
Car level, fill till it drains out the fill port, when down to a drip install the fill plug.
Melting Slicks
Joined: Jun 2019
Posts: 2,040
Likes: 928
From: near philly
As I recall, the Z06 has a differential cooler which must also be filled. The shop manual advises filling the diff, then running the drive train with the rear wheels off the ground to circulate the lube to refill the cooler. Then top-off the diff again to complete the refill.
I usually take a short drive instead of running with rear wheels off ground.
I usually take a short drive instead of running with rear wheels off ground.
Accessing that plug was pretty bad.
After I ran it the diff took about 2 more drops of fluid.
Total waste of time.
Race Director
Joined: Sep 2000
Posts: 11,143
Likes: 1,913
From: Missouri City, TX
the manual does recommend this, but I can confirm at least when I did it that it made zero difference and was WAY more work re-installing the fill plug to run it and then removing it again.
Accessing that plug was pretty bad.
After I ran it the diff took about 2 more drops of fluid.
Total waste of time.
Accessing that plug was pretty bad.
After I ran it the diff took about 2 more drops of fluid.
Total waste of time.
My experience as well doing diff fluid changes on the C6 Z06, C6 ZR1 and C7 Z06. Worrying about 2 or 3 ozs to get the diff totally full to the Fill port after the cooler lines purge any air is not worth the trouble. The cooler really does not drain with a typical DIY diff drain.