Rear Differential Fill Level Question
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Bent piece of wire for a dipstick.
Put in less than it calls for, then verify level as you add to desired level of 75W-90 Synthetic Axle Lubricant
Don't rotate the driveshaft during fill process, since the cold fluid will stick to the gearing and take a long time to drain back to 'level'.
Put in less than it calls for, then verify level as you add to desired level of 75W-90 Synthetic Axle Lubricant
Don't rotate the driveshaft during fill process, since the cold fluid will stick to the gearing and take a long time to drain back to 'level'.
Yeah, this ^^^^^^^^^^^^ a million times. I used to be in the trade, and I've filled THOUSANDS of diffs and trans (standard) using this method. Never, ever had one problem. And his point about the axle bearings is very relevant, those babies need to get some lube.
Overfilled will cause more foaming.
Foamed oil doesn't lubricate as well.
I was also trained to check that gearboxes (not just differentials, not just road vehicles) should be filled to the bottom of the check plug hole).
Times and recommendations change.
It's not difficult to get it to the recommended level.
Sometimes its difficult to identify the recommended level.
Foamed oil doesn't lubricate as well.
I was also trained to check that gearboxes (not just differentials, not just road vehicles) should be filled to the bottom of the check plug hole).
Times and recommendations change.
It's not difficult to get it to the recommended level.
Sometimes its difficult to identify the recommended level.
They amount below the hole depends on which differential / transfer case being looked at.
We (I) don't know where the hole is relative to the axle tubes / diff gearing / cover volume --- the instructions may put the lube at the same relative level for each axle version
OM for 2004:
For 3 rear axles, 3 different fill instructions,
(for whatever reason, the 1500 rear is the only one doesn't use the traditional bottom of hole as the high end of the acceptable range for the gmt800)
The proper level for the 1500 Series is from 5/8 inch to 1 5/8 inch (15 mm to 40 mm) below the bottom of the filler
plug hole.
The proper level for the 1500 HD Series, 2500 Series, 2500 HD, and 3500 Series is from 0 to 1/2 inch (0 to 13 mm) below the bottom of the filler plug hole.
The proper level for the 1500 and 2500 Series vehicles with QUADRASTEER™ (4 Wheel Steer) is from 0 to 1/4 inch (0 to 6 mm) below the filler plug hole.
Add only enough fluid to reach the proper level.
Also -- 4wd front axle
When the differential is cold, add enough lubricant to raise the level to 0 to 3/8 inch (9.5 mm) below the filler plug hole.
And transfer case instructions say:
If the level is below the bottom of the filler plug hole, you’ll need to add some lubricant.
Add enough lubricant to raise the level to the bottom of the filler plug hole.
Use care not to overtighten the plug.
They must have had a reason for each one to have different instructions
We (I) don't know where the hole is relative to the axle tubes / diff gearing / cover volume --- the instructions may put the lube at the same relative level for each axle version
OM for 2004:
For 3 rear axles, 3 different fill instructions,
(for whatever reason, the 1500 rear is the only one doesn't use the traditional bottom of hole as the high end of the acceptable range for the gmt800)
The proper level for the 1500 Series is from 5/8 inch to 1 5/8 inch (15 mm to 40 mm) below the bottom of the filler
plug hole.
The proper level for the 1500 HD Series, 2500 Series, 2500 HD, and 3500 Series is from 0 to 1/2 inch (0 to 13 mm) below the bottom of the filler plug hole.
The proper level for the 1500 and 2500 Series vehicles with QUADRASTEER™ (4 Wheel Steer) is from 0 to 1/4 inch (0 to 6 mm) below the filler plug hole.
Add only enough fluid to reach the proper level.
Also -- 4wd front axle
When the differential is cold, add enough lubricant to raise the level to 0 to 3/8 inch (9.5 mm) below the filler plug hole.
And transfer case instructions say:
If the level is below the bottom of the filler plug hole, you’ll need to add some lubricant.
Add enough lubricant to raise the level to the bottom of the filler plug hole.
Use care not to overtighten the plug.
They must have had a reason for each one to have different instructions
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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I have always reused the OEM gasket but those lube lockers are neat looking, never heard of them before.
Do you have a link or part # for that cover?
2010 GMC All Terrain 4x4 5.3 LC9 211k mi
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17,825 Posts
Well…did you fill to the hole or 5/8” below???
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
I filled it using the fill hole on back of the axle. The fill hole on the cover is tool low.
2010 GMC All Terrain 4x4 5.3 LC9 211k mi
Joined
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17,825 Posts
Now I’m confused. The full hole in the cover is the one you need to measure from for the level.
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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