Factory Rear Axle Info

[DYak]

I am trying to piece together info on the factory rear axles to see what opportunities there are for upgrade, interchangeability in the event of a trail break etc. If any of you have additional information, please post up below

What I have found so far (please correct me if I am wrong on any of this)
-All rear axles are an M220 gear set
-All rear diffs/shafts are 32 spline
-You can get an open diff or E-locker from the factory, is there a limited slip option?
-From what I can tell, they all run the same brake caliper with integrated EPB
-I am guessing that, similar to Jeep M220, they all run a set 80 bearing at the wheel.
-They all have the same suspension brackets

What I haven't found
-Some models have a swaybar on the rear axle, some don't. Does anyone know what options trigger this feature?
-Are there different axle housing widths?
-Do the different factory diff options change axle shaft length? I have heard that on Jeep Gladiator, depending on if you have a factory E-Locker or an LSD in your M220, there will be slightly different shaft lengths. What I am getting at here, is can you take a driver's side shaft off of any bronco and put it in any other bronco on the driver's side.

Have any of you had failures? I have heard of the tubes spinning in the center section. Have any of you bent axle shafts, tubes or blown up gears?

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[Bmadda]

Rear sway bar was added to 22+ 4dr w/sasquatch. AFAIK all housings had the mounting bracket. No LSD on any 6g Bronco. Only width change would be for Raptor which also gets dana 50 (whatever that is)

 

[DYak]

Rear sway bar was added to 22+ 4dr w/sasquatch. AFAIK all housings had the mounting bracket. No LSD on any 6g Bronco. Only width change would be for Raptor which also gets dana 50 (whatever that is)

Killer, thanks for the info.

I find it super interesting that some come with the sway bar and some don't. Would be curious if anyone has driven both variants and been able to notice a big difference

 

[Brian_B]

There is an aftermarket LSD -
M220 Eaton Detroit Truetrac Limited Slip Rear Differential 917A736
https://www.eaton.com/us/en-us/skuPage.917A736.specifications.html

Also aftermarket - there's also an ARB air locker and an Eaton E-locker (although I am unsure that the Eaton E-locker option is any better than the ELD from the factory). Plenty of ring/pinion gear sets. The bearings and rebuild kits are available (but often on a few weeks backorder)

From the factory it's just ELD or non-locker. The non-locker has the ring gear welded to the carrier, which makes it difficult to upgrade.

The rear end non-ELD and ELD versions have different axle lengths. The pumpkin is in a sligtly different location on the two different rear ends, so the shafts are off by about an inch from each other. For the front end it's similar: the m190 (non-ELD) has a different CV half shaft than the m210 (ELD version)

They do share all the same mounting points - so it's not hard to interchange between the FDUs or rear ends. The rear ends do share all the same bearings.

@BigMeatsBronco just shredded a m220 rear end not too long ago, he has a couple of good threads about it and his Dana 60 replacement process. I wouldn't call rear end damage too common, and BMB definitely is pushing the envelope there.

I'll also drop this here:
https://media.spicerparts.com/cfs/f...token=eyJhdXRoVG9rZW4iOiIifQ==&store=original

 

[Bmadda]

Killer, thanks for the info.

I find it super interesting that some come with the sway bar and some don't. Would be curious if anyone has driven both variants and been able to notice a big difference

In 2021 you couldn't order a factory roof rack on any 4dr sasquatch. It was the general consensus at the time that adding the sway bar eased engineering concerns about potential rollover stability when weight is added to the roof. Ford AFAIK never released any statement to that effect...but it's what we assumed. 2dr remained unchanged

 

[HPNQ420]

-Do the different factory diff options change axle shaft length? I have heard that on Jeep Gladiator, depending on if you have a factory E-Locker or an LSD in your M220, there will be slightly different shaft lengths. What I am getting at here, is can you take a driver's side shaft off of any bronco and put it in any other bronco on the driver's side.

Somewhere there is a thread about this and they were not. You'll need to search for it (use google adding site:Bronco6g.com after your search terms) but IIRC they swapped left for right and cut down one shaft or something similarly. But please look it up as my memory is fuzzy on it.

 

[DYak]

There is an aftermarket LSD -
M220 Eaton Detroit Truetrac Limited Slip Rear Differential 917A736
https://www.eaton.com/us/en-us/skuPage.917A736.specifications.html

Also aftermarket - there's also an ARB air locker and an Eaton E-locker (although I am unsure that the Eaton E-locker option is any better than the ELD from the factory). Plenty of ring/pinion gear sets. The bearings and rebuild kits are available (but often on a few weeks backorder)

From the factory it's just ELD or non-locker. The non-locker has the ring gear welded to the carrier, which makes it difficult to upgrade.

The rear end non-ELD and ELD versions have different axle lengths. The pumpkin is in a sligtly different location on the two different rear ends, so the shafts are off by about an inch from each other. For the front end it's similar: the m190 (non-ELD) has a different CV half shaft than the m210 (ELD version)

They do share all the same mounting points - so it's not hard to interchange between the FDUs or rear ends. The rear ends do share all the same bearings.

@BigMeatsBronco just shredded a m220 rear end not too long ago, he has a couple of good threads about it and his Dana 60 replacement process. I wouldn't call rear end damage too common, and BMB definitely is pushing the envelope there.

I'll also drop this here:
https://media.spicerparts.com/cfs/files/media/gKvvL6ujMaD8b5GND/LAXIP-0002-52022.pdf?token=eyJhdXRoVG9rZW4iOiIifQ==&store=original

That Spicer catalog is excellent, thank you very much. Also thanks for confirming that there are different axle shaft lengths. I find it interesting that the catalog says the shafts are different part numbers but they are one of the only items they did not tell you what the part numbers are. "contact vehicle manufacturer"

 

[Bmadda]

I have a pair of takeoffs handy if you need any measurements. They are from ELD/Sasquatch. Dont have any open diffs to compare.

 

[Brian_B]

I’ve got both an ELD and nonn-ELD rear end and posted axle measurements around here somewhere that can be dug up if needed.

 

[DYak]

@Bmadda @Brian_B I appreciate you guys. Brian I found the post you mentioned with length measurements, quoted below.

I have the open diff so I have been scheming on what to do with it. Personally I don't think I am going to be hard enough on it to warrant a UD60, especially since I just plan on going 37s. That said, if I am going to install a locker and regear, maybe even that RK rear end kit, it's a lot invested in the factory rear end.

What I think would be sweet is swapping the 32 spline side gear out of the ARB M220 locker for a 35 spline side gear out of one of their other diffs then getting some shafts cut. Dutchman does custom big bearing Ford shafts for under $500 a set on their website so there you have the 35 spline inner, set 80 outer, all you need is the tone ring press. Obviously the devil is in the details but there are probably worse ways to spend $500 and a boat load of time.

I had the opportunity to pick up a takeoff 4.46 Locker rear end, so I was able to pull shafts from both the Standard and Locker rear ends and set them side by side.

It appears the pumpkin sits a bit to the left on the Locker version compared to the Standard.

Here are the shaft measurements - don't take these to the bank, this is me eyeballing with a tape measure.

Standard
Left - 33 1/4" stamped 92
Right - 37 3/16" stamped 97

Locker
Left - 32 3/8" stamped 22
Right - 38 1/8" stamped 21

Photos - parallax makes the tape not quite look like what I eyeballed it at - again, I wouldn't take it to the bank.

Left shafts - tape on Standard

Left shafts, tape on Locker

Right shaft standard

Right shaft Locker

Pic showing the stamp on the hub, this is Standard Left

 

[BigMeatsBronco]

good info right there...so I have a pair of m220 "locker axles" and the e-locker available I'm not using.

 

[DYak]

Nice are those the ones where you shredded the gears? Looking to build those things back up?

Also would be interesting to know if the ELD and non-ELD diffs are interchangeable within ELD/non-ELD housings. I am guessing no since ARB lists their M220 locker as not compatible with Jeeps or Broncos that came with the factory E-Locker

 

[87-Z28]

Good info right here. Thanks. When details are flushed out please compile in first post.

I have been contemplating this also. I think with a light and skinnier 37 the OEM rear end will be fine if you don’t beat on it. At least for my use case. I have a 22 non SAS and it has mounting locations for rear sway bar. Not sure I am going to add it if I don’t go with 4 link rear. Still thinking thru that and waiting a bit. I think you need to be committed to your use case to invest a bunch into the oem m220. That is what I am struggling with.

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