Filling up an older style (86 or 87?) 3.23 posi rear disc 10-bolt rear end through the breather plug. So far, I've used up 2 quarts of fluid, and I'm wondering if I need another quart. How much fluid would I normally need? In situations like this, I'm used to filling it up until it reaches the top of the fill hole (like the T-5, for example). Right now, it doesn't seem like it's anywhere close to it. Is 2 quarts enough, or should I buy an extra quart? thanks!

 

I always buy three and end up putting two in.

 

I've never had one take more than two quarts.

 

Hmmm me either. I think I usually buy 3 as well but end up using a little under two of them. Specs that I've read have said 1 3/4 quart, and that's probably about what I use. I use a little hose-pump thing and pump a little into the rear. Then add my GM posi additive to the bottle of diff fluid, pump the rest of that bottle in, and then pump whatever it takes of the second quart..usually 3/4 or so.

If it were me, I'd keep filling until I saw fluid dribble out of the fill hole

 

Make sure you fill the differential to where you can feel the fluid when you stick your pinkie finger into the fill hole ON THE SIDE... If you fill it up to where it comes out of the vent (on the top of the pumpkin), it will be WAY overfilled... The fill plug is on the passenger side, and it takes a 3/8" extension on a ratchet to loosen...