2024 Silverado 1500 (SU8/G80 + AAM SU4) – differential specs

[BodarkMan]

Hey guys,

 

I’ve got a 2024 Silverado 1500 and I’m trying to get ahead of maintenance on the diffs, but I’m running into a lot of mixed info.

 

Truck setup:

 

• Rear: GM SU8 w/ G80 locker, 3.23 gears
• Front: AAM SU4

 

What I’m confused about:

 

1. Gear oil – does it really matter if I stick with ACDelco OEM?
   I’m seeing the recommended ACDelco fluid isn’t very easy to find (especially for the rear).
   • Are there solid alternatives (amsoil, Valvoline, etc.) that meet spec?
   • If so, what is that spec other than just 75w85 
2. Where are you guys actually buying the OEM fluid?
   I’m not seeing much availability online (Amazon, etc.), so wondering if dealer is basically the only option.
3. Gaskets:
   • I’ve read the front diff doesn’t use/need a replaceable gasket
   • Does the rear diff cover need a new gasket, or is it RTV from the factory?
4. Service intervals:
   For relatively mild use (some towing/hauling, nothing extreme), what intervals are you guys actually running for the front and rear diffs?
5. Where are you getting official info? Is everyone just using the GM service manual / SI subscription, or is there another reliable source I’m missing?

 

 

Appreciate any insight

[davester]

No any fluid will work, just put in what the manual says, 75w85 or 75w90 (it'll vary for whatever reason).  Lots will say they include limited slip diff additives.  They are fine, just don't add any other additive to the rear diff for the G80.

I buy a good synethetic oil and it's good to go.

 

I would look at the diff, you can tell if it's got a gasket or sealant.  You can also check for drain plugs, front diff might have one, rear isn't likely to.  Also look to see how much room there is around the fill port for the diff.  My diff's have enough space, so I can use 1qt bottles, tilt them mostly upside down and squirt directly into the diff, w less clearance, getting fluid that's in a bag makes it easier to do, or you can get a manual pump to get it into the diff.

 

The diff's are pretty reliable, so I would do it sooner than the regular interval but longer than the extreme service one.

 

I recommend a subscription to it at alldata.com.  They are running a special right now, up to 30% off their subscriptions.

[Transient]

2.  www.rockauto.com

 

4.  Iirc, you only need to service the differentials if you have a leak.  There is no service interval listed in the manual. 

 

5.  Owners manual, which I access through the MyChevrolet app.

[dennismc]

When I had the front and rear diffs serviced I used Amsoil Severe Gear 75W-80 synthetic gear lube.

my 21 Sierra has SU4 front, SU7 rear.

[22SLT]

I have a 2022 Silverado with the same setup as the OP (SU4 front, SU8 rear).  Part numbers are Canadian. 

 

After considerable research and lots of youtube:

 

1. SU8 gasket is reusable.  GM part number 84412728.  The SU8 requires AC Delco 75W-85 GL-4 fluid, GM part number 19368514.

 

2. SU4 gasket is one-time.  GM part number 84428297.  The SU4 requires ACDelco High Efficiency Gear Oil 75W-85 GL-5 fluid, GM part number 19300457.

 

Edit:  The picture of GM part number 19368514 shows GL-5 on the label, not GL-4.  So I did more research.  It seems the "SU8" is irrelevant for fluid purposes.  What is relevant is if you have the G80 locking differential.  I do have this one and the problem is it has brass and copper mechanisms.  The sulfur-based additives in GL-5 will react with those metals so you need GL-5 gear oil with "non-reactive, buffered sulfur-phosphorus additives".  Apparently a degree in chemical engineering would also be useful.

 

Amsoil Severe Gear and some others use those 'non-reactive' extreme pressure additives and that is why they are compatible with the G80/SU8 combination.  

 

Also FYI:  the transfer case uses Dexron VI synthetic automatic transmission fluid GM part number 88865549, but you can get any Dexron VI from Mobil/Valvoline/Amsoil.  

 

And in case you have it, the 8L90 MQE transmission (8-speed) uses Mobil 1 Synthetic LV ATF (blue label).  Which is equivalent to Dexron HP.  Hope this helps.

Edited June 3 by 22SLT
Additional information added.