What kind of car is that out of?

 

You replied to such an old thread from 2001, that I just split it off into its own new topic.

A 9-bolt rear end came in some 85-89 Pontiac Trans Ams, as well as some 87-89 IROC Camaros. There were a few leftovers installed in 1990 f-bodies as well. They were stronger than the 10-bolt and so installed in the higher horsepower cars, the 350 TPI's and the 305 TPI's with 5-speeds and the G92 performance package. Its distinguishable by the 9 bolts holding the cover on, as well as the rubber fill plug in the center of it. Its full name is the Borg Warner Australian 9-bolt rear end, and yes it was made in Australia and imported into the USA for the thirdgen f-bodies. However, it became too expensive, so GM went back to the 7.625 10-bolt in the 1990+ models.
The 9-bolt has a ring gear size of 7.75", and used bolt-in axles instead of holding the axles in with a c-clip like a 10-bolt. These two characteristics made it stronger than the 10-bolt. Available gear ratios were similar to 10-bolts as well, with 2.77 replacing the 2.73, 3.27 replacing the 3.23, and 3.45 replacing the 3.42. There is also a 3.70 gear set for the 9-bolt from the aftermarket, and those are basically the only gears left you can buy new.
If you have more questions, you can ask here, or do a search on this forum to find out yourself.