If you can get a socket and extension on the 2 bottom nuts that hold the pumpkin into the center housing it's an 8 inch. If you cannot get a socket and extension on them it's a 9 inch.

 

if you are really lucky- look for a small tin plate approx 2 in long attached to the rear end. It will have the size, and ratio on it

 

Most people, even mechanics, often think that an 8 inch is a nine inch. They think that all V8 cars came with nine inches and that 8 inches are 4 lug. None of which is true.

 

Post a picture, we can tell if it is a 9" instantly.

If the tag is missing try this.

To check if it is an open differential or a Trac-Loc jack up the rear end. Try to turn one wheel, if both wheels turn in the same direction it is a Trac-Loc (or something similar), if only one wheel turns or the two wheels turn in the opposite direction it is an open differential.

To check the gear ratio put masking tape on the rim and on the drive shaft. If the rear is a Trac-Loc elevate both rear tires and count how many revolutions of the driveshaft you need to get the wheels to turn one full revolution.

If it is an open differential just jack up one rear wheel and turn the drive shaft and count how many revolutions it takes for the wheel to complete one full revolution and then divide that number by two.

 

8".....

 

Will get a photo uploaded later this evening

 

Just went out to the garage. Took these 2 photos. Does it help?

 

lookin like an 8 to me

 

Looks like a 9" to me. The outside edge of the carriers on the nines tend to stick out by each bolt, the eights seem to have a smooth line. Further it looks like a socket would not fit on the bottom bolt as I think the case sticks out (that is the easiest test, see if a 9/16" socket will fit). On an 8" the socket goes on straight, on a 9" it get pushed off center by the protruding case. 8" also have about 6 inch flat sections on the top and bottom, this one doesn't seem to have those.

Just check to see if a socket fits on the bottom bolt.

I think it looks a lot like the gray nine inch shown on this page. http://lonestarbodyshop.blogspot.com/2012/04/ford-8-9-diff-id-and-specs.html

 

Looks like a 9 to me. The center hump on the back of the housing is typical to the nine. Also check this page out:

http://www.maliburacing.com/ford_9_inch/ford_nine_inch.htm

 

Also, based on the www.maliburacing.com/ford_9_i..._nine_inch.htm web site, look at the pinion support. This is for sure a nine inch rear end.

 

OK then I stand corrected- (I was looking at the lowermost nut- thinking you could get a socket on it- on my 9 inch that one at the 6o clock and the one at about 7 or 8 oclock also can't get on it) My bad

 

It's a 9"