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Rear Differential Fill Level Question

757 Views 15 Replies 8 Participants Last post by  canyon56, 
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Any tricks and tips for not overfilling my 2003 Sierra 1500 Z71 rear differential fluid. The factory recommendation is to fill 5/8" to 1 5/8" below the fill hole when the oil is cold. Thanks for sharing your wisdom.
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I just purchased and painted a new rear differential cover. It is OEM GM, but this one has a fill plug. I also purchased a LubeLocker gasket just to make sure it’s easy to install and leakproof. I’ll tackle the fluid change on the rear and front differentials along with the transfer case this weekend.

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Just finished changing the rear differential oil and cover. Thanks for all your help!
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04z71tx said:
Do you have a link or part # for that cover?
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Here you go.

2003 GMC SIERRA 1500 5.3L V8 Differential Cover | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.
www.rockauto.com
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nealinator said:
Well…did you fill to the hole or 5/8” below???
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I filled it using the fill hole on back of the axle. The fill hole on the cover is tool low.
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nealinator said:
Now I’m confused. The full hole in the cover is the one you need to measure from for the level.
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I think the cover with the fill hole I used is for newer model gm trucks. I left the fill plug off the cover and filled from the original fill hole. Oil began coming out of the cover fill hole well before it reached 5/8 inch below the axle fill hole.
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