I have a 9 bolt rear... I plan on siphening out the fluid,, anyone see any negatives in doing this instead of unbolting the cover? How much fluid does it hold? The guy at pep Boys told me 3.5 quarts, is this correct? How much GM posi additive do i have to add? And where do i get it? Only GM has it? is the part # 1052271? any other info is appreciated :lala:

One plus to removing the cover would be to allow a visual inspection of the 'guts', as well as to see how much, if any, metal shavings are stuck to the magnet. Outside of that, and the gear oil being rather thick, I know of no reason why you couldn't siphon it out and refill. Not sure of the exact quantity of fluid, but it should just start to seep out of the fill hole when the proper amount has been reached; I believe you add the entire bottle of posi additive...it's just a couple ounces, maybe.
A quick check showed 3.5 pints instead of quarts to fill the housing.

Pete

Yeah, I siphoned my 9 bolt a few weeks back. Drawbacks - it takes longer, gear oil tastes terrible, you can't inspect the rear, and it is hard (but not impossible) to get all of the old oil out.

Remove the cover. You'll be glad you did.

Pulling the cover is the only sane way of doing this. Siphoning will not get everything out, and any particles will tend to sit at the bottom where the siphon won't get them.

If you use AMSOIL Series 2000 gear lube, you won't have to worry about the additive (it's in the lube). Check the Yellow Pages for a dealer in your area, or order from www.amsoil.com. It's much better stuff than you'll get at Pep Boys.

Pull the cover (for all the reasons above). Capacity is 1.7 qts and I also use the GM additive on my 9 bolts.

Miles
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