Differential mix matching

Posted by: Blu

Differential mix matching - 05/03/20 04:27 PM

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?
Posted by: RF_Overlord

Re: Differential mix matching - 05/03/20 04:32 PM

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...
Posted by: Blu

Re: Differential mix matching - 05/03/20 04:45 PM

Originally Posted By RF_Overlord
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?
Posted by: 2004_p71

Re: Differential mix matching - 05/03/20 09:13 PM

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 .
Posted by: Blu

Re: Differential mix matching - 05/03/20 09:53 PM

Originally Posted By 2004_p71
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.
Posted by: 2004_p71

Re: Differential mix matching - 05/04/20 07:36 AM

Originally Posted By Blu

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 .

Posted by: Blu

Re: Differential mix matching - 05/04/20 09:58 AM

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.
Posted by: Blu

Re: Differential mix matching - 05/04/20 01:56 PM

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!
Posted by: 2004_p71

Re: Differential mix matching - 05/04/20 09:20 PM

welcome sir , glad I could help smile
Posted by: Blu

Re: Differential mix matching - 05/14/20 07:28 PM

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.








Posted by: 2004_p71

Re: Differential mix matching - 05/14/20 10:41 PM

looks like the pinion is too far away .
Posted by: Blu

Re: Differential mix matching - 05/15/20 12:41 AM

Thanks, kind of what I was thinking. Working on it tmrw
Posted by: Blu

Re: Differential mix matching - 05/15/20 04:03 PM

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

Observations?




Posted by: 2004_p71

Re: Differential mix matching - 05/16/20 08:38 AM

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

Re: Differential mix matching - 05/16/20 12:08 PM

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.
Posted by: 2004_p71

Re: Differential mix matching - 05/17/20 08:43 AM

so you have 2 shims on it then ?
Posted by: Blu

Re: Differential mix matching - 05/17/20 03:57 PM

Correct 2 shims.

Going to play around with swapping internals later just to see if it can be done or not...
Posted by: 2004_p71

Re: Differential mix matching - 05/17/20 09:49 PM

I have always been lucky enough to only have to use one shims . I heard mixed opinions about stacking up shims.
Posted by: Blu

Re: Differential mix matching - 05/18/20 12:52 PM

They seem like they would be pretty secured from a rocking/extruding problem. They are underneath a pressed in bearing. Two tapered roller bearings with an oil film should soak up enough of that drive/coast shock to not be an issue. The only thing I could see getting sloppy is if the crush sleeve collapses more after sometime. What are the potential issues?
Posted by: 2004_p71

Re: Differential mix matching - 05/18/20 01:14 PM

Some shims were not made exactly the same way and would have an edge that would prevent the shim from sitting perfectly flush with the other one . The pinion nut requires lots of of torque to crush the sleeve so I dont see why it would cause an issue but like I said from what I read online there are mixed reviews .
Posted by: Blu

Re: Differential mix matching - 05/18/20 02:06 PM

Ok, I get what you're saying. I noticed that the thicker shims in the kit were die cut from plate steel while the thinner ones were cut from shim stock, which is typically ground and hardened. But even if there was a burr, the fact that the shims are squashed under that bearing and rechecked gear pattern/backlash shouldn't make much difference..?
Posted by: 2004_p71

Re: Differential mix matching - 05/18/20 10:35 PM

I guess not but once again I never had to deal with that so who knows .

after reading the ford procedure you posted it looks like using two shims is normal procedure after all
Posted by: professorP7B

Re: Differential mix matching - 05/21/20 09:59 AM

Not to hi-jack a thread entirely, but looking to get some thoughts on a 3.55 axle swap on my '11.

Reasons:

1. I've been noticing some acceleration whine clearly coming from the rear end that's progressively getting worse.

2. I noticed a squeaking noise when going over bumps at first, then I found I could get the noise to happen simply by bumping the car back and forth by hand against the parking pawl. Had a friend do that while I looked underneath and noticed the pinion flange sliding in and out of the axle housing by about 1/8" and was able to stop the noise by forcing my hand up against the flange. SOOO, the pinion bearings are likely on the outs. (I can see a pinion seal was installed recently, before I bought it. I know they obviously didn't tear it down and replace the crush sleeve because when I changed my gear oil it was black as night.)

3. I found a complete 3.55 axle assembly out of an '06 with 13k on it for $300 bucks.

4. I don't have the interest time to teardown my axle (while re-gearing it to 3.73.) 3.55 is close enough (currently has a 3.27 trac-lock.)

I'll replace the axle seals on it before installing, and since I'm pulling the axle I'll also likely install some Heinous control arms and a Metco watts linkage while I'm in there. Anything I'm missing here?
Posted by: 2008interceptor

Re: Differential mix matching - 05/21/20 12:32 PM

You may want to have the ecm tuned to reflect the higher gearing. Earlier you could change out a spedo gear but now it uses a vss sensor instead I believe. I went 3.08open -3.55 lsd on a 98 towncar. It was driveable but shifted early, yours is less of a difference than mine though. Mine would hit the Rev limiter under heavy throttle and not shift. You may just have the speedometer be off and slightly earlier shifts.
Posted by: 2004_p71

Re: Differential mix matching - 05/21/20 10:54 PM

Originally Posted By professorP7B
N
2 I looked underneath and noticed the pinion flange sliding in and out of the axle housing by about 1/8"


wow that is really bad !
Posted by: professorP7B

Re: Differential mix matching - 05/22/20 07:28 PM

Yes I plan to tune the ECM for the new ratio accordingly. Any preferred tuners? I'll make/ask on a more dedicated thread for heavy details. I don't plan on using any canned Mustang tunes included with the unit, but am interested to see what's best.
Posted by: professorP7B

Re: Differential mix matching - 05/22/20 07:31 PM

Yeah it's one of the worst I've seen. I cranked on the nut to take up some of it, not that that's an acceptable repair. But it'll let me do the light, around-town driving I'm doing now per the shutdown. 3.55 axle from an '09 CVPI w/16k on it is currently on it's way. That unit I mentioned in my first post wasn't available.
Posted by: 2004_p71

Re: Differential mix matching - 05/23/20 09:59 PM

Originally Posted By professorP7B
Yes I plan to tune the ECM for the new ratio accordingly. Any preferred tuners? I'll make/ask on a more dedicated thread for heavy details. I don't plan on using any canned Mustang tunes included with the unit, but am interested to see what's best.


got with marty .
I had an sct tune on my 2011 and ran ok but the tune for the crown vic are very generic . i got a tune from mart not even a week later and it,s a whole different car now