2009 LMM CC/SB ~16,500 miles

I have read through several threads but still am confused as to what to expect for the proper/normal level in the G80 rearend, checked 10 to 15 minutes after you stop running the truck, the level is about 3" below the hole on the back cover, or just about as far as you can reach with your finger.

I rechecked the owner's manual and it says to only check it after a couple of hours to allow all of the gear oil to settle back into the pumpkin. It also gives the caveat that it is filled by volume and not by level. And still could not find an answer as to how far below the hole the normal level should be.

I believe elsewhere I read that it takes about a gallon of 75W90 synthetic to fill it when changing the oil. Have not planned to change the oil for several thousand miles yet, but may consider it from what I read in other posts.

The main reason that I ask is when I back out of the garage I have to make a hard left turn and this gives a shudder for a few feet of travel and then goes away, I also read elsewhere that is relatively normal for a G80 locking differential.

To me an oil level approximately 3" below the cover hole is too low and may be the reason for launch shudder from stopped when initiating a turn. :confused:

You could add a little bit but I dont think that it is the cause of your shudder.

I like to be able to dip my little finger just below the hole and get lube on my fingertip. I'd go ahead and add some lube. It might solve your problem or it might not, but lube all the way to the fill hole won't hurt anything.
To my knowledge (which is limited), a G80 is either locked or it isn't. I doubt it would be the cause of your shudder, but I'll defer to someone more knowledgeable.

a lot of people have found the rear diff low on oil. not sure if gm leaves them low from the factory or if they use oil breaking in. down that far is not a good thing. when you change it i would not try to overfill it. if you do overfill it you will probably be changing some seals very soon. from memory i think the correct level is within one inch below the fill hole. ( i think )