What size ring gear in 1985 Oldsmobile delta 88?

The 1985 Oldsmobile Delta 88 typically came with a ring gear size of 8.5 inches for the rear axle. This size is associated with the GM 10-bolt rear differential commonly found in many GM vehicles of that era. However, it's important to verify the specific axle type and gearing ratio for your particular vehicle, as variations may exist.