Aside from the 4oz of GM posi additive, how many oz/quarts does it take to fill the rear?

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1989 IROC-Z 5.7L

 

I'm not sure exactly, just fill it all the way up until it starts coming out the drain plug then plug it up real quick.

 

It is supposed to be 3.5oz of posi additive along with 1.75 quarts of 80-90W gear oil. Putting more additive will not hurt anything. I put a 7oz tube of additive in mine and put a little less gear oil.

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87 Camaro Z28
LB9 305 TPI, Accel cap, rotor, and 8mm wires, K&N filters
1/8 mile: 9.8@69mph

91 Formula
L98 350TPI, Accel 8.8mm wires, Siamese Runners, Edelbrock Headers, Edelbrock 3" Cat-Back, Airfoil, K&N Cone Air Filter, AFPR, Shift-kit, Mallory Promaster Coil, Nitrous Works Wet Kit 75hp
1/8 mile: 7.9@86mph

 

Assuming you haven't done this yet: It takes just under 2 qts.

Get ahold of some AMSOIL Series 2000 75w90 gear lube. It has the friction modifier built into it - you don't need the extra stuff. And, you'll get the benefit of the synthetic base.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/LB9 block, ZZ3 cam and intake, WP 305 heads ported & polished, Hooker headers & y-pipe, 3" Catco cat).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, 3.08 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

ok.... does this additive realy work.... lets have some input on it!!

 

Yes, the additive really works IF you're using a dinosaur juice-based lube. But, as I said, use the synthetic and you don't have to worry about the additive.

 

i recently put a used "locked" rear end in my truck with 3.42 gears, and I was going to change the fluid in it, would i beable to tell a differece if that pozi fluid was added?

 

You should ALWAYS use the GM posi-additive when you change the fluid in your posi rear end. Unless you use synthetic fluid, like was said above.

 

Even with synthetic gear oil I use the GM additif,it won't hurt at all!!