2015 Yukon - Change both diffs' oil and transfer case fluid early on

[SuperOldSchool]

Just sharing my experience with everyone. 2015 Yukon Denali with 39k miles.

I changed the gear oil in both differentials and the transfer case fluid today. Used Amsoil Severe Gear 75w-90 and their Synthetic ATF, which is compatible with Dexron VI. I wish I had done this at 5k or 10k miles. See below...

The transfer case fluid was still red and not too dirty. No pics of the fluid, but here was the magnetic plug before and after.
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The rear diff fluid was a little dark, but still transluscent. Not too much paste on the magnetic plug. The cover and diff gears were a little dirty, so I sprayed them with brake cleaner to remove the black coating.

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The front diff was the shocker! Oil looked like gray paint with a good amount of metal paste on the magnetic drain plug. I rarely drive in Auto or 4WD, so not sure how this came to be. Glad I changed it!

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Regards,
SuperOldSchool

 

[salanizi]

Wouldn't changing the diff oil cause the new light oil not to be thick enough to compensate for the wear of the metal parts and thus cause premature failure of the diff components?

I thought general mechanical knowledge is that diff oils are better not replaced...???

 

[SuperOldSchool]

Wouldn't changing the diff oil cause the new light oil not to be thick enough to compensate for the wear of the metal parts and thus cause premature failure of the diff components?

I thought general mechanical knowledge is that diff oils are better not replaced...???

I have never heard that. In every 4wd vehicle I've had, I have always changed that oil at some point. It's a maintenance item.

 

[Tungsten2016lt]

What about tranny fluid. What weights for transfer case and rear end. Will be buying amsoil oils too. My tahoe has 47k miles now.

 

[SuperOldSchool]

I listed the gear oil and trans fluid (for transfer case) in the first post....this is a 2015 Yukon with 8 speed.

The 8L90 transmission requires Dexron-HP spec fluid. I have read the trans fluid swap is not as straight forward as days past. I've always done my own cars in the past, but may leave this one to the dealer at 45k. ( GM replaced my trans at 15k, so I'll be ready when odometer hits 60k)

Read this:http://www.gm-trucks.com/forums/topic/179503-8-speed-oil-level/

 

[sumo]

Never to early. It's too late is usually the problem

 

[01SLE]

I had the exact same result on the font diff. 50k miles, 2016 SLT 4x4

 

[James Ward]

Hi everybody, Either I'm not seeing it or I'm just stupid, but I have 65000 miles on my 2015 Tahoe LT and I'd like to change the Transfer fluid, and the front differentials, What kind of Fluids or oils am I going to need and what the procedure, I did a search and this seemed like a good spot for me to ask this question, and My truck has a posi-traction 3:08 in the rear was a rental/ lease vehicle, so I have no idea what kind of life it lad. Thank you !

 

[Flyboygt]

from what i can find:

Front diff Amsoil Severe Gear 3 pints
Rear Diff Amsoil Severe Gear 5.5 pints
T-Case Amsoil Signature Synthetic ATF 3.2 pints

info found on their website
https://www.amsoil.com/lookup/auto-...-3l-8-cyl-engine-code-c-l83-c-flex/us-volume/

I would suggest new gaskets for front and rear diff covers. you will need to research your vehicle to figure out what axles you have for the seals.

As for a write up to complete all these... start searching. sorry.

Diff fluid is easy. remove the diff cover bolts on the bottom first then loosen all the rest of the bolts and it all comes pouring out. clean RG and Diff and housing with brake cleaner. install new gasket and cover. fill through filler plug.

T-case- i havent been under the ** yet to see where the drain and fill plugs are but probably the only 2 screw caps on the case, one on bottom other prob on the side.

a hand pump is handy to have to get the fluid into tight spots. something like this:
https://www.amazon.com/Plews-586430...t=&hvlocphy=9033151&hvtargid=pla-764078689165

good luck

 

[SuperOldSchool]

Hi Original poster update.
I’m at 94k and just did my transfer case and both differentials again today - 55k on the oils.

front diff oil was spotless - still golden in color and transparent. Very little paste on plug:

Transfer case plug had a little paste, fluid cherry red:

Rear diff plug had barely any paste. Cover had some dark oxidation, but not as much as the 39k change. Fluid was translucent, but a little dark:

I do not tow and drive a good mix of stop and go and highway.

Conclusion for my habits and experience is to change the factory fill early (I waited until 39k, but next time I’ll do it around 15-20k) then again 60k later. Then I’d leave it be. The condition this time was so good, I didn’t really need to do it.

Hope you guys are seeing similar results with your changes.

Amsoil Severe Gear 75w90 in differentials and Valvoline synthetic Dexron VI in the transfer case.

Good fluids will last a long time.

 

[SuperOldSchool]

OP again. Changed rear diff oil today. 63k on Amsoil Severe Gear oil - 75w90, 158k on truck.

Magnetic plug had a little paste- same as last 2 times. Inside of cover was a little dirty / oxidized.

Sprayed out the gears with brake cleaner, wiped off magnet in pumpkin.

I thought last time was my last change, but glad I did it again. 60k seems like a fair interval for this truck and my driving habits.

 

[SuperOldSchool]

Last Sunday also did transfer case fluid - 63k on fluid, 158k on truck. Fluid was nice and red. Magnetic plug not bad.

 

[TheBigCheezeBall]

I am wanting to change the rear differential oil in my 2017 2WD Tahoe. I am a bit confused on if I need to have the "limited slip" additive or not though.

I have the following RPO codes for the diff: GU4 and G80. Which indicate a 3.08 with positraction / limited slip.

I was going to use Mobil 1 75W90 LS: https://www.mobil.com/en/lubricants...ucts/products/mobil-1-syn-gear-lube-ls-75w-90

However I am not sure if the "LS" is ok? Should I instead use the version without LS? There seems to be some conflicting information about this.

 

[SuperOldSchool]

You don’t want to add additional LS additive, but you can use that Mobil gear oil just fine.

 

[SuperOldSchool]

OP again, just did front differential again. About 64k on the oil.

Plug was pretty clean and oil was not filthy at all, could have probably left it ( as stated in my last change), but my OCD won’t let me…..

Out with Amsoil SevereGear 75w90, in with Valvoline synthetic 75w90.