2024 Sierra - changed rear differential and transfer case fluids

[zogg]

My 2024 Sierra 1500 with a g80 locker has 66,000 miles. Time for some work. The rear differential oil looked really clean but I replaced it with delvac 75/90 oil without the limited slip. I read that it had a reusable rubber gasket…not correct. So halfway through the job I went autozone and Oreilly for a new one. Not available. Found one at the gmc/ buick dealer.
The transfer case oil was black..surprisingly nasty. Replaced it with red dexron vi as per owners manual. Everything seems great

 

[RamFan]

Does the G80 not require gear oil with LS additive?

Side note - I just dropped the trans pan, swapped t-case fluid, and rear diff fluid in the CX-5. Must have been driveline week.

 

[Jimmy_Russells]

I did both diffs in my wife's Subaru a few days ago too. I always am reminded about how bad gear oil smells

 

[wlk]

Does the G80 not require gear oil with LS additive?

Side note - I just dropped the trans pan, swapped t-case fluid, and rear diff fluid in the CX-5. Must have been driveline week.

Pretty sure it's does, maybe wrong though

 

[Rand]

Pretty sure it's does, maybe wrong though

G80 is an auto locker, not a friction based limited slip.. no additives wanted or needed.

 

[GSCJR]

I'd be willing to bet that Delvac 1 already has the LSD additive in it.

 

[RamFan]

G80 is an auto locker, not a friction based limited slip.. no additives wanted or needed.

Good to know, thanks!

 

[I<3oil]

I'd be willing to bet that Delvac 1 already has the LSD additive in it.

They make a Delvac 1 LS and a regular Delvac 1 without LS.

S

Thread '75W-90 Synthetic WITHOUT Limited Slip Additive - Mobil Delvac?'

Mar 3, 2024

So, I am changing the rear axle oil in my 2003 Dodge Ram 2500. It has a Limited Slip differential in it (helical type), and generally, it's understood that no friction modified or LSD additive is necessary. Also the Dodge user manual (with poor punctuation) appears to say, NOT to use any Limited Slip Additive, but to use a Synthetic gear oil. Ok, fine, but it appears there are very few 75W-90 Synthetic gear oils that are available for a "normal" price (less than $30/gallon). I have not subscribed to the typical "higher grade" oils, like Redline and Amsoil for +$20/quart. It's hard to...

• Spddm0n
• Replies: 27
• Forum: ATF, Differential, Trans, Brakes, P/S

 

[GSCJR]

A gear oil without additives is not easily sourced around these parts; I learned something today.

 

[johnmyster]

G80 is an auto locker, not a friction based limited slip.. no additives wanted or needed.

Incorrect. G80 has clutch packs in the side of the carrier that get compressed, transferring torque between the spider/side gears and the carrier. I was ignorant to how they worked for many moons until @dnewton3 schooled me about it here:

Post in thread 'Fluid for 2013 GM 4x4'

Mar 4, 2025

Don't bother with FM:

Completely incorrect and that thread you linked is rife with inaccuracies and falsehoods.


The G80 in the trucks IS a clutch driven device. It is only called a "locker" because the cam-ramps which clamp the clutch packs do so with enough force to fully "lock" (no slippage) for torque bias.

Go to the Eaton website and look at their product page. You'll see the "M Locker". That is the unit which was used by GM.


There was a GM document WAY BACK in the day where a...

• dnewton3

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[barkingspider]

You did good w Delvac 1 75w90, no LS. You are good for another 66k miles. I’m surprised the gasket was not reusable as most modern GM trucks have the coated steel ones. Good you got one from the dealer. What brand dex vi did you use in the transfer case?

 

[4wd]

I'd be willing to bet that Delvac 1 already has the LSD additive in it.

It’s going to have FM anyway and thousands of these do have clutches - but used differently than limited slip.
I used Delvac 1 in the GM G80’s for many years …
But word of caution - the G80 code from GM indicates its function - so dive deeper to verify what AAM put inside.
Surprised by the gasket - I used to just crack bolts until the oil ran out (2nd and 3rd change - not first) …

 

[4wd]

The IRS in Tahoe/Yukon et al - does use a GM LSDA.
I used these two - then did figure 8’s in a big parking lot. LH turns had a sound/feel. Third bottle cured this.

 

[4wd]

Here are some more comments on the RPO code -
again, dig deeper …

https://www.autoevolution.com/news/a-simple-guide-to-the-g80-locking-differential-94874.html

 

[STL_G8GT]

Not sure I understand the difficulty in finding the right spec fluid, unless it goes hand in hand with limiting customer access in repairing their own vehicles...?