[Cj1]

OK. I called AC Delco/Genuine GM parts directly. They looked up what came in car factory fill and they state with confidence that the ZL1 should use part number #88862724, which is the 10-4034 LS Gear Fluid. That's all you need as it has the additive in it already. They also said they can not say whether or not you can use #88900401 as an alternative with the #88900330 additive.


I spoke with a guy at the parts department of a Chevy dealership, and he seemed very unconfident and unsure, but he said you can go either way. His words were they are basically the same thing one just has the additive in it already.

[302crossram]

so the 10-4034 is synthetic ??

I'm thinking no

[FarmerFran]

So the moral of this thread...

Do not change the factory fluid until you are sure what fluid to put in?

[Caerus]

Was trying to use ACDelco, but I want a combined synthetic with friction modifier without mixing a concoction. So far have not seen that version yet. I went to the Redline website and looked at OEM compatible products (for a 2023 ZL1) and this is the one I probably will use. It meets the specifications for the GM gear oils below that have been listed in this thread. I have used Redline before for most of their products and they worked fine.

GM 19352759, GM 88862624, GM 88862625, GM 88863089

Does any one have any thoughts on this option?

https://www.redlineoil.com/75w90-gl-5-gear-oil

[SnakeEyeSS]

^ beat me to it.

[SnakeEyeSS]

Originally Posted by Cj1

New part numbers...



88900401 lubricant

88900330 additive



You'll need 2 bottles of the lubricant and 1 of the additive

Those can't be new numbers, Amazon shows it for sale since 2013.

[Greg83]

I just left my dealership today. They used my vin number on my 2022 SS-1LE (same E-Dif as ZL1) to look up the correct dif fluid. They said to use the synthetic 10-4016 and add the friction modifier. The parts guy wasn’t sure but he didn’t think the 10-4034 (with the modifier already) was synthetic.
The saga continues!!!

[Rock-It Man]

This is the right stuff:

Dexron 75W-90 GM p/n 19352759. No friction modifier required. This is what comes up when I search and when the dealer searches.

I got this fluid installed in my ZL1 at about 1600 miles and no issues. The dealer flushed out the diff with this oil and then filled with this oil.

[GreenZLE]

Every limited slip EXCEPT a detroit locker needs a friction modifier as far as I know. In other words, if it has clutches in it, it needs a friction modifier. 10-4034 is what I've always used. If they stop offering it with the friction modifier, I guess I'll just buy a bottle of a name brand friction modifier.

[Warrior102]

Rock-It Man's research is correct, thats because the E-Diff doesn't require a friction modifier, the clutches are located in a separate circuit that uses automatic transmission fluid to control clutch engagement levels. In a standard limited slip spring pressure maintains clutch engagement until axle rotation overcomes the friction, modifiers prevent the clutch pack from chattering. the E-Diff can engage the clutch from 0 - 100 percent or anywhere between via separate computer controlled hydraulic circuit so no chattering. That said having it will likely not cause a problem but it's not required as the clutches are in another housing. Mobil1, AMSOIL and Royal Purple all make excellent 75W-90 without the additive, GM sources it's gear oils from various suppliers. I use this with excellent results on my 1LE and Sierra's locker. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[FarmerFran]

JTDC!

[Rock-It Man]

Originally Posted by FarmerFran

JTDC!

Use your words.

[cdb95z28]

This is comical.
Straight from the service manual:


US #88862624 (AC DELCO 10-4034) INCLUDES MODIFIER
CANADA# 88862625 INCLUDES MODIFIER

Now whether these #s have been updated is another story but the 88862624 IS still available.

Makes no difference if the diff is in an SS 1LE, ZL1 or ZL1 1LE. It's all the same diff, eLSD.

[FH212]

Originally Posted by cdb95z28

This is comical.
Straight from the service manual:


US #88862624 (AC DELCO 10-4034) INCLUDES MODIFIER
CANADA# 88862625 INCLUDES MODIFIER

Now whether these #s have been updated is another story but the 88862624 IS still available.

Makes no difference if the diff is in an SS 1LE, ZL1 or ZL1 1LE. It's all the same diff, eLSD.



Attachment 1137332

This is what I did. I looked in my owners manual and did my Diff fluid change with #10-4034.