So I pulled my rear end apart to put in the carbon fiber clutches. Turns out its open carrier. bummer.

As usual the hoard provides, a seperate assembly. LSD carrier 28 spline, boo, the axles are 31 spline.

The cross pins are different sizes too. What determines the size of the cross pin?

The open diff has the larger pin. What do I need to make the 28 spine carrier into a 31 spline?

I measured both differentials, the bore that the axles go through are the same size.

What's really different on the 28 vs 31 LSD carrier? The holes for the cross pin?

The number of splines on the axle shafts and the spider gears they go through, for one. Not sure if you can mix & match like that...

You think just side gear set would need to be swapped? https://www.americanmuscle.com/ford-31spline-88-spidergears.html#product_pics-0

Now wondering about the cross pin, does it need to be the smaller diameter to accommodate the clutch packs and spring?

You cant mix and match the 28 and 31 spline diff internals, they are two different units and nothing can be swapped over from one unit to the other one .

Just want to be clear, when you say internals you mean hard parts, everything except the clutch packs?

I'm still thinking the carriers are the same with different sized cross pin holes.

Here on the picture you can see the difference between a 28 (left) and a 31 (right) diff .



The difference in the carriers are subtile but the cast is different.



The side and spider gears do not have the same shape and are more square on the 31.



The spring is also bigger on the 31 spline unit but still offers the same preload on the clutch pack. It is bigger to match the new size of internals.



The very only thing being the same as you already know if the clutch pack .
I didnt bother to try 28 splines internals in a 31 splines carrier or vice versa but without a doubt just because of the cross pin diameter difference you can do that .

Thanks a bunch for those pics! They cleared up some gaps in my info.

I thought that the 31 spline open just looked like that because it was open and not LSD. Now I see that there is more material instead of small ribs opposite the ring flange.

Pretty much summed up what I needed to know for now.

You cant just take swap the internals even if you opened the cross pin holes 1/8th inch? This is something im going to play around with, just out of curiosity.

Anyways, in the mean time, I'm probably going to hit the junkyard to find a suitable explorer diff.

Apparently, the Explorers are sitting either crooked in a manner I wouldn't get underneath or are just parked normal instead of the stands they put the cars on. no bueno.

Grabbed a diff from an 07 F-150, it has the ABS notched ring flange. $33!

welcome sir , glad I could help

So its an F-150 LSD carrier and new 3.73 gears/bearings.

Posting these to get a second opinion on gear mesh pattern!

resistance added with 15 pinion revolutions forward and 15 revs reverse to set marks.

looks like the pinion is too far away .

Thanks, kind of what I was thinking. Working on it tmrw

Dropped another .015 shim on, its .037 total.
Looks pretty evenly centered on all sides to me.

Observations?

How many shims do you have stacked now ?
yes pattern looks good to me .

Thanks for helping!
The stock one from the original was .037" total. .022" from original pinion and .015" from the shim kit. I dont know why I even bothered pulling that shim from the original because nothing is original anymore, so it wouldn't matter. I bought 2 of each shim kits just to have options. Its only been apart 4 times now lol.