c5racr1

Changed the diff fluid in my 17 GS A8, 1 full quart low from the factory. Check your diff fluid!!

0Cajun @ Edgyvette

Ours also.

X25

I wonder if it's since they don't run the car to fill the lines and the cooler​ core to check the level again? Still, you'd think factory would find a way to compensate for that. What I found was that the factory fill was highly pressurized. Perhaps the air in the lines added to the air pressure when the oil pump primed the lines.

c5racr1

No idea, but Gm needs to fix that.

99mike

My GS was 1/2 quart low and Eng Oil sump was 1 qt. over.

vetteandv

What fluid are you using to top off the diff with?

dbaker

The trans fluid in my Z51 was about 1/2 qt low.

Changing the diff fluid soon.

\db2

cvp33

Partly because I was preparing for a track day(s) and partly because of these threads, I had my dealer switch me to Mobil1Delvac - 75/90 full synthetic. No worries now.

TEXHAWK0

Welcome to the club. GM has been underfilling differentials since 2014. They come from the manufacturer already filled, and most dealers do not check it in the PDI.
My 2014, non-eLSD, was also almost a qt. low even without oil coolers.
I think it is just a ploy by GM to save the cost of a qt. of fluid on every car~

Also, the service manual says that 1/2" below the fill hole is still within the acceptable operating range.
My guess is that even if the oil cooler lines are filled when the car is running, some fluid still drains back to the differential when you stop the car to check the level, so you are never going to have all the lines filled and the level at the bottom of the hole.

I went ahead and changed my fluid and brought it up to the bottom of the hole.

LivinTheDream

My base '17 was not filled either, and the plugs barely more than hand tight. Very glad I changed it out at 700 miles.

tobaccokid

Just had my dealer check the diff fluid in my new (got it new just before the winter set in) 2016 Z06 when the 500 mile oil change was done. Level was fine.

Ag3ofshadows

Completely unrelated but do you hear a clicking noise when you turn right/left coming from the front tires on your GS?

0Cajun @ Edgyvette

Yep. I saw a TSB on rocks getting stuck in caliper or hub or something. You can really hear it when inside a parking deck or enclosed area. I just usually do a HUGE burnout and it goes away Just kidding

Ag3ofshadows

thats where I originally heard it, somehow over the exhaust lol, and it's bothered me ever since.

C2367

Easy fix, take the fill lug out 3/8" and add a 1/2 Qt. of 75-90 LS. Very simple.

jagamajajaran

Regarding differential fluid level, the manufacturer's fill level measurement is very precise. The assembly plant can access the records of the amount that goes into each unit. It is part of their track and trace data that is collected during the supplier manufacturing process. That said, they never look into the diff but simply assemble it into the chassis. Leakage is almost non existent, as it would spill on the external case, and they would find this in their audits.

Lastly, since the manufacturer fills to a mass, using a scale system, and not to a specific level, differences in castings, gear sets, etc., can cause a difference in the level, which they do not measure. There is no issue with the level being low, but if you crack it open, there is no way to fill as the manufacturer did due to the fact you cannot get all the fluid out before refilling. This is why the service procedure is to refill until the level is at the access hole…just like we did on every old school diff out there. In other words, you can think the diff is half a quart low because the level isn't at the access hole, but since you can't remove all of the diff fluid to see how much is really in the system, you can't truly ascertain if it is actually low.

tcmc5

Prepping for first track event, 1600mi on '17 GS, and found diff 1 quart low. Ridiculous.
Glad I'd come across this thread!

jagamajajaran

Please refer to post #16. Just because you can add fluid using the old standard of fill until it won't take any more fluid doesn't mean it is low.

ersatz928

I think that the lubrication of the gears depends on the fluid level...not the mass of the fluid....they might fill it by mass at the factory, to save time/money (Filling it till it runs out of the hole makes a mess and wastes fluid), but apparently that doesn't allways ensure that the level is correct.

https://www.corvetteforum.com/forums...sd-issues.html

c5racr1

Based on the fluid fill procedure outlined by gm, mine was a quart low. Your reply sounds like " gm said ls7 heads are fine". You are speaking in hypothetical, we are speaking actual.