[silicon212]

Originally Posted by deesandvees

When I turn a tire the other tire spins in the opposite direction and the driveline doesn't turn. But if I rotate the tire back and forth a few inches repeatedly the driveline turns as I'm doing it.

Not sure the rear end size, the diff cover measures about 10.5"x11.25", not sure if that helps decipher if it's a 8.5" or 7.5". My lug configuration is 5x4.75 not 5x5 if that helps. There's a code in the trunk that tells what it is isn't there?

Some of them have a code, some do not. If you see a "G87" in the trunk, it's an 8.5", but if you don't see that, it doesn't mean it isn't. G89 is definitive proof of a 7.5". The rear cover on the 8.5" seems to stick out a good distance and the pan itself is oval shaped, while the 7.5" has a less protrusive cover and is more of a rounded square shape. The easy way to tell the two apart is by looking at the bottom of the differential casting - a 7.5" will have, on the bottom, on either side of middle, a machine pad with a 'hook' shape while the 8.5" will have square shapes sticking out below the cover.

This is an 8.5" (it's the diff on my car):



closeup of the square machine pad:



and here is a 7.5" for comparison: