Axle differences

[Joseph Burgess]

Ok , ive got a 2000 Expedition Eddie Bauer, 4x4 with the auto 4wd. Getting ready to replace my rear diff due to problems, was going to just sway the entire rear with another donor. Here is my problem i have a limited slip diff axle tag is S939 J with the 3.55 ratio ive noticed that in my search for compatible axles ive found a S939 P but according to fords page these are 14mm studs and it doesnt list mine as having the 14mm studs. First question would be if mine does have 12mm studs can i just swap the axles with mine aslong as the ratio is the same. Oh yea my axle code is H9 aswell 3.55Ls any help would be greatly appreciated.

 

[Killer Ride]

Cant you just switch the studs?

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[Joseph Burgess]

Thats what im trying to find out honestly dont know, can i switch the studs only or do i need to switch the axles aswell

 

[ExplorerTom]

When was yours built?

 

[Joseph Burgess]

Good question i think if i remember correctly Dec 1999, but ill have to get back to you on that

 

[Joseph Burgess]

Ok build date i was wrong on it was August, 99 axle code is H9

 

[ExplorerTom]

I’m pretty sure the switch to 14mm studs was late in 1999. I seriously doubt you can just swap lug studs. You might be able to swap axle shafts though- depending on what’s wrong with your current axle.

 

[Joseph Burgess]

Im thinking its in inner pinion bearing or ring and pinion gear, bad whirling sound at speed, if the axles are the same spline then swapping will be easy

 

[captain chaos]

You cannot just swap studs. Swapping axle shafts, maybe, but not just studs.
Also, the larger studs use a slightly different center cap (lug cover) for the wheels so they don't interchange; I ran into this problem on my 2000.

Besides measuring the studs themselves to see what you have, the easiest way to tell is by lug nut size.
12mm studs will take a 19mm(3/4") socket.
14mm studs will take a 21mm(13/16")

 

[Joseph Burgess]

Well looks like im either gonna have to have it rebuilt or swap both front and rears to match, all i can locate is the 3.73 gear rear ends and that wont work to well with my front 3.55, if i can find a front 3.73 then id like to just swap both for the better ratio oh and yes i have a 2000 model with 12mm studs