[MrGoodwrench]

Hello All, I just serviced rear axle oil and the 8 speed transmission (filter and fluid) on 2016 C7, Z51 at 39500 miles. I know the manual is calling for this service at 45 K, but l like to do the services early then later and I am glad I did, the oil and fluid were very dark. When I dropped the transmission pan I only got 6.5 quarts of fluid and that’s what I put back, when I warmed up the car per instructions to see if I have the right amount, a half cup of fluid came out of over fill hole. Does this mean that GM had too much fluid in the transmission?
The other question I have is the half cup of fluid was still dark and I wanted to change the fluid again within 5K miles since all the fluid did not get changed, but i don’t want to drop the pan and there is no drain plug. Can fluid be sucked out with a pump from the fill plug?

Just yesterday I changed the fluid and filter on my 2014, Special Edition Z-51, 6-speed. I also changed my filter & fluid early at 39K. There is no way to extract extra fluid other than to just let it run out.
I used the factory manual procedures to drain and refill the fluid. After bringing it back up to the recommended temperature to check the fluid I also noted dark ( NOT black, original) fluid drain first , followed by fresh red fluid. The GM factory manual says the dark fluid is not a problem unless you are also seeing solids like band pieces.
I live in Wisconsin so, it will be a while before putting mine back on the road and to check the level for “true” accuracy. Hope this helps! It’s a LONG winter in Wisc.!