10-bolt

From Camaro Wiki

The 10-bolt rear end was the base rear on 1st through 4th generation Camaros. It got the name 10-bolt because there are 10 bolts that hold the differntial cover to the housing.

The 3rd and 4th generation cars only had a 7.5" ring gear that was smaller and weaker than the rears on earlier cars. It is common for the rear to break on these cars, especially when used with sticky tires.