Defcon 1

Hello Everyone,

I have a 2003 Avalanche 1500 Z71 w/ 4.10 gearing and was wondering what type of differential fluid I need to use. I am a little confused because my manual doesn't specify if the rear differential with LSD takes a different type/viscosity of fluid compared to the rears without. Also, do I fill the oil level to a certain depth or until it comes out of the fill plug hole? This will be my first time doing this on this truck, so any advice is very much appreciated, thank you.

KChevy75

I'd follow what the manual says. 75W-90 Synthetic. 5/8" to 1-5/8" from the fill hole. Don't add limited slip additive as if you have an RPO G80, its a locking differential, not limited slip and can cause chattering and excessive wear. TSB #91-4-109. If RPO G80, you might want to fill it 0" to 3/4" from the bottom of the fill hole.

If I remember correctly, the capacity is about 2.5 quarts.

I use Mobil 1 75W-90 in the 3.73 G80 locking diff in my suburban with no problems.