Uh...it's all in the manual, dude. Give it a read.
http://www.camaro5.com/forums/showthread.php?t=33993
Rear Axle (V8 Engine)
Rear Differential Fluid 75W-90 Limited Slip to GM Specification 9986226.
GM Part No. U.S. 89021677 and Friction Modifier 1052358,
in Canada 89021678 and Friction Modifier 992694.
Rear Axle
When to Check Lubricant
It is not necessary to regularly
check rear axle fluid unless you
suspect there is a leak or you hear
an unusual noise. A fluid loss could
indicate a problem. Have it inspected
and repaired.
How to Check Lubricant
A. Fill Plug Hole
B. Drain Plug Hole
To get an accurate reading, the
vehicle should be on a level surface.
If the level is below the bottom
of the filler plug hole, add some
lubricant. Add enough lubricant to
raise the level to the bottom of the
filler plug hole.
What to Use
For 218 mm rear drive module
(RDM) V6 manual, V8 automatic
and V8 manual:
To add lubricant when the level
is low, use 75W-90 LS gear oil
(GM Part No. US 89021677
and 1052358, in Canada
Part No. 89021678 and 992694)
meeting GM Specification 9986226.
To completely refill after draining,
see Recommended Fluids and
Lubricants on page 10-7. Then fill
to the bottom of the filler plug hole
with the Synthetic Gear Lubricant.
For 195 mm RDM V6 automatic:
To add lubricant when the level
is low, use 75W-90 gear Oil
(GM Part No. US 89021677,
in Canada Part No. 89021678)
meeting GM Specification 9986115.
To completely refill after draining,
see Recommended Fluids and
Lubricants on page 10-7. Then fill
to the bottom of the filler plug hole
with the Synthetic Gear Lubricant.