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Discussion Starter · #1 ·
Changed the fluid in the rear differential. The amount of fluid that I removed was ~2.25 quarts, and the fluid I put back in was ~3.25 quarts. I put fluid in until it ran out the fill plug. I wonder why the difference?

Used Mobil 1 75W-90 gear oil.
 

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Discussion Starter · #6 ·
the 10.5 takes 3.25QT / 9.5 2.7QT .. now on filling with the vehicle LEVEL in warm weather fill to just below the fill hole. in cold weather fill to 1/2in below the fill hole. this fluid when hot expands.

since you drained out A QT less then you must have a leak. check the fluid every oil change for level and fluid color.
My truck has the 8.6" ring gear. I have your standard 10 bolt G80 locking diff. There are no leaks on the axles, pinion or other areas. The truck is a 2013

After reading a BUNCH of posts on other forums I gather the capacity of that particular diff is ~2.5 quarts. Many have said that the proper fill level is 0.5" below the fill plug.

I filled the diff up until it came running out of the fill plug and waited for it to stop running out. Is this improper, I don't know, I've always filled gearboxes up until the fluid came running out of the fill plug.
 

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Discussion Starter · #8 ·
I have a 10.5", and I want to remember the 10.5" is "level with the fill hole"; but I do know it depends on the differential.
You must have a 2500 Silverado.

I was under the impression that the 2500 and 3500 rear differentials were made by Dana while the 1500 diffs were made by Eaton.
 

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Discussion Starter · #10 ·
Before this thread gets too far off topic:

I would like the opinion of some of the forum members as do they think that filling G80 8.6" differential on a 2013 SIlverado up to the fill plug is bad, good, does not matter?

Thanks.
 

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Discussion Starter · #13 ·
I never seen a diff go bad from too much fluid. some say the seals could get damaged from pressure build up.

I know that if the vehicle is not level you can put 4.5 QTS in it . or put in 1 qt too little. if the front end is high you can overfill very easy.
I was under the impression that differentials have some kind of venting system on them so too much pressure cannot happen.
 

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Discussion Starter · #19 ·
So all in all it sounds like just fill the diff until it comes running out the fill hole.
 
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