GM 88900401

[Ditchdoc1017]

I have a 2021 Chevy Tahoe z71 it started making a low speed noise in the rear end. GM service bulletin advise changing the diff oil multiple times. I had a mechanic do the first change he used GM
88900401. It has gotten worse. What would be a cheap brand that I could do several drain with. Also is there a good additives I could use.

 

[Boomer]

That should still be under warranty, yes? Have it checked by the Chevy dealer and document the problem.

 

[Ditchdoc1017]

Has 80000 miles

 

[Rand]

supertech brand at walmart.

 

[zfasts03]

Usually that is for the front diff. and 75w-85 for the rear part number 104091,

19300457​

if that is the same as my 16 Suburban.

but the 75w-90 might be a better option for protection, slight hit on fuel economy.

 

[Ditchdoc1017]

Has 80000 miles

It only low speed started while turning right when cold now it’s both ways. After the service

 

[QuantumS4]

To the OP: I assume the Z71 package includes the G80 auto locking rear diff? I have a 2023 Silverado LT that has the G80 diff and I think I’m having the same issue as you. When it’s below 40 degrees outside and the truck is cold I get a binding/howling when turning either direction for a few hundred feet when I start off. I don’t have the free time to play the game with the dealership to leave it over night and have them tell me they can’t replicate it so I’m considering 2 flushes with some 75w-90 that I have already and refill with the GM 10-4091. I’d be curious to know how it goes for you.

Here is the best deal I’ve found on 75w-90 GL5 diff fluid:

Amazon.com

Good luck!

 

[Ditchdoc1017]

I’m

To the OP: I assume the Z71 package includes the G80 auto locking rear diff? I have a 2023 Silverado LT that has the G80 diff and I think I’m having the same issue as you. When it’s below 40 degrees outside and the truck is cold I get a binding/howling when turning either direction for a few hundred feet when I start off. I don’t have the free time to play the game with the dealership to leave it over night and have them tell me they can’t replicate it so I’m considering 2 flushes with some 75w-90 that I have already and refill with the GM 10-4091. I’d be curious to know how it goes for you.

Here is the best deal I’ve found on 75w-90 GL5 diff fluid:

Amazon.com

Good luck!

we’ll just done my second flush it loud but not as loud as the first one.
One of my pilots that does a lot of Mx work says he think something broken but mine only turning straight it’s fine.