Semi VS Full-Float, How can I tell?

[The Butcher]

I got a rear D60 the other day from a guy for cheap. He claimed it was out of an old Dodge, but he didn't know the year. All he said was it had a new posi, and 4.11s in it. How can I tell if this is a 30 spline SF, 35 spline SF, or a 35 Spline FF? What are the external visual clues (without opening the diff) to tell if an axle is a SF or a FF?

Also, if you were going to eventually drop a bigblock into your K5, and run at least 38s, would you use this D60, or opt for a D70 or 14bolt? Thanks!

 

[divorced]

If the axle shaft is bolted in, it's a full float. Here is a pic of a FF, you can see the 8 bolts (circled in yellow) that hold the axle shaft in.

 

[neverendingproject]

Full float
http://www.coloradok5.com/techpics/14boltsideview.jpg

and a semi float
http://www.coloradok5.com/atrondiskbrakes/74disc06.jpg

I personally think that a D60 will be okay if its a FF, but you might want something else if its a SF.

 

[The Butcher]

Thanks guys. I'll have to take a look at it this weekend since it's not at my house. If it's a FF, do you think it will stand up to 44s and a big block? Or should I look for a 14 bolt FF or a Dana 70? I appreciate your help.

 

[neverendingproject]

Its up to you, I think 14FF are a tad beefier, parts are chaeper, but D60 has better gear selections

 

[rustyear]

i would go 14 bolt in a heartbeat...it will bolt right in, they are cheap and plentiful, its way stronger than a D60 or a 70, (set up correctly, you will never break it), and it's simple to set up the gears, even. Make sure it is the full float 10.5 ring gear variety (these will have the 8 bolts holding the axle in, in the hub area). If you find one that has 3/4 ton brakes and want to go with 1 ton, no problem...just bolt 'em on. A detroit locker is cheap, (prob about $325 now), as opposed to a locker for a dana axle. Also, disc brake conversion stuff is all over the place if you wanna go disc and most of these use all gm parts, (except for caliper brackets)...the 14 bolt full floater is the king of truck axles, up to about 2 ton or so