DIY: Rear diff fluid change - 2018 Sierra 5.3L 4x4

Bob2C · October 4, 2020

What stinks is there is no drain plug on the front differential on the new 2019's. It is also harder to get to the fill plug. The harness for the power steering is in the way.

That’s insane. Why would they not put a drain plug?

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TXGREEK · October 4, 2020

That’s insane. Why would they not put a drain plug?

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Oh boy, so much more than we all know

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TXGREEK · October 4, 2020

Here's the front diff job, not much different (30000kms / 18500 miles)

1. locate the front diff plugs, loosen the top fill plug first, then the bottom drain plug second
2. drain fluid
3. refill with your favorite gear oil (i used Amsoil 75w90, same as the rear diff)
4. tighten plugs back to spec

Some observations:

the old fluid was a dark green as opposed to the dark black from the rear diff. I only use the front diff occasionally in the winter with AUTO mode, and very rarely in 4 HI, so that likely explains the colour difference, it's not used as much. I tow a 3000lb and a 5000lb trailer boat about 2000 miles a year.

I drained approximately 1200 ml out, and refilled with 1600 ml back in.

Gotta love da Amsoil!

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mookdoc6 · October 4, 2020

7 hours ago, TXGREEK said:

Highly recommended replacing the crappy rear Diff cover with a new G2 as it makes replacing the fluid a breeze!

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Same one I got SON! I just squeezed in 4qts of EZ-Pack in mine couple weeks ago!

TXGREEK · October 4, 2020

Same one I got SON! I just squeezed in 4qts of EZ-Pack in mine couple weeks ago!

You make me feel so young lol. This is my second one, I stripped the top bolt on the first one, this one is replacement, I’ve got one more for just in case [emoji6]

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MY164X4 · October 7, 2020

Here's the front diff job, not much different (30000kms / 18500 miles)

1. locate the front diff plugs, loosen the top fill plug first, then the bottom drain plug second
2. drain fluid
3. refill with your favorite gear oil (i used Amsoil 75w90, same as the rear diff)
4. tighten plugs back to spec

Some observations:

the old fluid was a dark green as opposed to the dark black from the rear diff. I only use the front diff occasionally in the winter with AUTO mode, and very rarely in 4 HI, so that likely explains the colour difference, it's not used as much. I tow a 3000lb and a 5000lb trailer boat about 2000 miles a year.

I drained approximately 1200 ml out, and refilled with 1600 ml back in.

Thanks.

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UnlimitedMatt · October 7, 2020

On 10/4/2020 at 7:35 AM, TXGREEK said:

Highly recommended replacing the crappy rear Diff cover with a new G2 as it makes replacing the fluid a breeze!

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I have been thinking of doing the same thing but I got sucked down a rabbit hole with my research. Did you see Gale Banks research on differential covers?

TXGREEK · October 7, 2020

I have been thinking of doing the same thing but I got sucked down a rabbit hole with my research. Did you see Gale Banks research on differential covers?

It’s all BS, Banks has made a brand for himself years ago and now entering the already over saturated Rear Diff industry. I love my G2 Diff Cover, works fantastic and very easy to work with. I’m not a supporter of manufacturers that dog on others when his is no different than the ones that have been out for a VERY long time. G2 has an outstanding customer service department and bring that I OffRoad often, the G2 cover is extremely strong custom manufactured with proper honing etc and looks great. I wouldn’t hesitate to buy one. I bought three, messed up the first one by over tightening the upper fill bolt and forgetting to add washer so now I’ve got one left lol.

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davester · October 7, 2020

What's BS about his video's for his testing of those covers?

1) he found some had the fill port at a different level than OEM, and some by quite a bit. Lower level may not lube properly, higher level puts more drag on the diff, and also puts more heat into the fluid

2) he found that the interior shape around the ring gear affects how the fluid flows around it. If it's more squared off instead of rounded, the fluid goes up instead of around, then falls down into the oil coming from below, causing more aeration.

Neither of these things are bs, They are basic design failures by those cover manufacturers.

From looking at G2 covers, your cover definitely has a problem with 2, and you can't tell if they got 1 right. However, for 99% of buyers, like you, the diff isn't worked anywhere near where the cover makes a difference, other than hitting it with a rock. It's just bling.

TXGREEK · October 7, 2020

What's BS about his video's for his testing of those covers?
1) he found some had the fill port at a different level than OEM, and some by quite a bit. Lower level may not lube properly, higher level puts more drag on the diff, and also puts more heat into the fluid
2) he found that the interior shape around the ring gear affects how the fluid flows around it. If it's more squared off instead of rounded, the fluid goes up instead of around, then falls down into the oil coming from below, causing more aeration.

Neither of these things are bs, They are basic design failures by those cover manufacturers.

From looking at G2 covers, your cover definitely has a problem with 2, and you can't tell if they got 1 right. However, for 99% of buyers, like you, the diff isn't worked anywhere near where the cover makes a difference, other than hitting it with a rock. It's just bling.

Now that you’ve once again targeted one of my comments. It’s BS, he’s made a big issue with a non existing issue, he’s marketing his products on assumptions that others haven’t done their homework on, these have all worked for people like me that follow what the experts use, never questioning or focusing on cost.

Now, how about you show proof that G2 has ever failed? A company highly respected by professionals world wide, better yet, show where any rear end failed due to running after market rear Diff covers. Never going to happen so why don’t you go back into the hole you “once again” crawled out of.

Good bye [emoji112] [emoji112]

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Brian2015 · October 8, 2020

YYC-Sierra, thank you for the write up. I was going to take my truck to the stealership but after seeing this, I picked up AC Delco 75/90, 75/85 and AC Delco full synthetic trans fluid and did the rear diff and transfer case myself tonight. Doing the front diff tomorrow.

This was the first service at 52K and to be honest, the transfer case fluid was still red, the rear gear lube was dark but not a whole lot of metal on the magnets. I feel better now that it's done. I would have done the front diff tonight but I have a skidplate that needs to be removed, didn't feel like doing it in the dark.

Granite7 · October 8, 2020

YYC-Sierra, thank you for the write up. I was going to take my truck to the stealership but after seeing this, I picked up AC Delco 75/90, 75/85 and AC Delco full synthetic trans fluid and did the rear diff and transfer case myself tonight. Doing the front diff tomorrow.

This was the first service at 52K and to be honest, the transfer case fluid was still red, the rear gear lube was dark but not a whole lot of metal on the magnets. I feel better now that it's done. I would have done the front diff tonight but I have a skidplate that needs to be removed, didn't feel like doing it in the dark.

I’m going to be doing the same thing over the winter. I see you went with the full synthetic ATF. What made you decide synthetic over the standard?

I’m a little puzzled that the full synthetic is much cheaper on Amazon.

davester · October 8, 2020

3 hours ago, TXGREEK said:

Now that you’ve once again targeted one of my comments. It’s BS, he’s made a big issue with a non existing issue, he’s marketing his products on assumptions that others haven’t done their homework on, these have all worked for people like me that follow what the experts use, never questioning or focusing on cost.

Now, how about you show proof that G2 has ever failed? A company highly respected by professionals world wide, better yet, show where any rear end failed due to running after market rear Diff covers. Never going to happen so why don’t you go back into the hole you “once again” crawled out of.

Good bye

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Well, it is not a non-issue.

Sure, for people like you who buy it for it's appearance, it appears to work fine, as you basically have to want to make a cover wrong in order to get the diff to fail because of it. That it aerates the oil more than the oem cover, or that it causes the oil to be a little hotter than with the oem cover just slightly decrease the overall lifespan of both the oil and the bearings/gears in the diff, and if/when the diff happens to fail, a mechanic would not attribute the cause to the cover because it would just look like the oil failed.

But, under more demanding conditions, such as what Banks demonstrated in his videos, it can make a difference.

I'm sorry you are that emotionally invested with a couple hundred dollar cover that you can't admit, in this case:

-more aeration in gear oil is worse than less aeration, and your G2 cover does aerate the oil more than the oem cover

-the wrong oil level in the diff is worse than the right oil level in the diff (I don't recall if the G2 cover has the right level or not)

TXGREEK · October 8, 2020

I’m going to be doing the same thing over the winter. I see you went with the full synthetic ATF. What made you decide synthetic over the standard?

I’m a little puzzled that the full synthetic is much cheaper on Amazon.

Full synthetic isn’t 100% Synthetic unless it says it’s 100% synthetic. Full synthetic is a mixture of lower end oils mixed with 100% synthetic additives.

I’d look at the Amsoil squeeze packs 75w90 100% synthetic, far superior protection and longer life.

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Brian2015 · October 8, 2020

18 hours ago, Granite7 said:

I’m going to be doing the same thing over the winter. I see you went with the full synthetic ATF. What made you decide synthetic over the standard?

I’m a little puzzled that the full synthetic is much cheaper on Amazon.

I went with AC Delco Dexron VI full synthetic at the recommendation of a friend who builds racing transmission and race cars. He is a GM guy, and engineer by trade. He has a Silverado 3500 that pulls his car hauler and gigantic camper. For what I do (daily driver, hauling a light load (5x8 landscape trailer hauling tree stands, ATV hunting gear, tree trimmings).