I need to change the fluid in my starange 12 bolt it has the LPW aluminum cover with fill and drain plugs.

looking at it it seems that if i fill to spill then the diff will be over 3/4 full of fluid, as the fill plug is rather high on the diff cover

Is this correct - does one fill to spill or is there a set amount of oil and additive to use?

Thanks

 

I have a strange 12 bolt w/ aluminum cover also. When I changed mine, I used 2 quarts of fluid and one bottle of the GM additive. Those were the instructions that I got with the rear. I put the same amount in that I got out of it. Personally I think 2 quarts is too much because after about a quart and a half, it started to come out of the check plug on the side of the pumpkin.