Yukon 5.13 Gears in Factory M210 Housing: It Fits!

[Hey Buddy]

I like what @Just_Jim did with placing the locker switches next to the window switches on the center console, so I'll probably copy him. I plan to buy the connectors on Ebay or Amazon and wire them up myself rather than using Ford's harness.

I cannot wait to see this one on YouTube!!

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[BigMeatsBronco]

As I mentioned elsewhere on the forum, I've been gathering up parts to do a drivetrain overhaul on my 2-door Base non-Sasquatch, which currently has an M190 front end, open diff of course, and 4.46 gears due to the manual transmission.. So I bought a used M210 FDU and M220 rear axle assembly that had come out of a Badlands Sasquatch, so they already had the electric lockers. The FDU still had the factory 4.70 gears but the previous owner had re-geared the rear end to 4.88, so they were mismatched anyhow and I was going to have to re-gear at least one end to match them up. But part of this upgrade also entails 37" tires (currently running 35's) so I preferred to re-gear both axles to an even deeper gear.

Like many here believed, the conventional wisdom has been that any gears lower than the factory 4.70 simply would not physically fit into the factory M210 gear case. As is often the case on the Internet, this was first said, and then repeated, by people who carry some authority on the subject, in a YouTube video. So voila, instant fact. But I'm always one to question authority

I'm pretty good friends with the guys up at Yukon due to my industry connections so I called up there and asked if they knew anything about it. They said of course, they actually have gears specifically designed for the Bronco M210, all the way down to 5.38. I chose to go with 5.13's (I'll explain why later), so I ordered R&P's and install kits for front and rear.

So yesterday I had a chance to load everything up and haul it over to my buddy Mike's shop (4XDoctor) in Riverside to set these up and independently verify, for myself and for the rest of the Internet, that yes indeed you can re-gear the factory Bronco M210 to lower than 4.70. Now, Mike is mostly a Jeep shop doing straight axle gears out of Jeeps and Early Broncos, but he'd done a few IFS front drive units so he was somewhat familiar with them. But I'm not going to say the Bronco M210 FDU didn't throw him a few curveballs. But he figured it out and got it all set up. The final result is that the gears fit fine, the setup went fine, all of the bearings, shims, crush sleeve and seals that came in the Yukon install kit were correct for the application (not simply re-purposed from the Jeep JL M210 as some have found with other install kits). Basically, once we figured out how everything comes apart and goes back together, everything went smoothly and fit just right.

So the FDU is now buttoned up and back sitting on the bench in my own shop ready to be installed. It got late on us so I left the rear end with Mike to do at his leisure and I'll pick it up later this week. But there was no question about the M220 so I didn't see the need to hang around for that. I won't actually get these installed into the Bronco for at least a month though, as I'm waiting on some other stuff to come in so I can do everything at once. So I can't give you any seat of the pants or performance results yet but I can only verify that yes the Yukon gears do fit and everything in their install kit fits and works as intended.

So, about that Internet myth. I believe there are two things at work there. First, it was a claim made by the guys who have a vested interest in selling the very expensive complete "Ultimate" FDU. So there was an incentive to simply say their product was the only way you could get deeper gears into a 6G Bronco. Second, I believe the "deeper gears won't fit" claim was based on an early state of affairs, in which the only M210 aftermarket gears were specifically made for the Jeep JL version of the M210, and perhaps those did indeed not physically fit, at least back at the time that claim was made.

But the Nitro 5.29's have been out for a while, and those were just verified for fitment on this board a couple of days ago. I don't know how long these Yukon's have been on the market. But it looks like we now have a couple of options for deeper gears in the stock M210 FDU. So we can put that Internet myth to bed.

As an aside, Ford themselves now offer 5.13 and 5.38 gears pre-loaded in complete FDU assemblies through Ford Performance, in what appear to be factory FDU housings (not a re-branded Dana Ultimate housing). And of course Dana makes those too. But as of the last time I checked, neither Ford nor Dana offer those Ring & Pinion sets by themselves without having to buy the complete FDU.

Lastly, some have asked why I chose 5.13 gears, why not go deeper to 5.29 or 5.38. I came up with it after playing with Grimmjeeper's excellent gear calculator. I remember when I first got my Base-non-Squatch with MT, and it was on the stock 30" pizza cutters. To me it felt like it was too torquey for comfortable street driving. It felt like 32" or maybe 33" tires would have been perfect for that drivetrain. When I went to 35's it felt slightly under-geared. The stock final drive "crawl ratio" for my Bronco was 79.92. Going to 5.38s would have put me at a crawl ratio of 96.41 on 37" tires, which is slightly lower than the stock Sasquatch crawl ratio of 94.75, while highway RPMs at 75mph would be 2367. In the stock congifuattion on 30" tires, its was turning similar rpms at highway speeds (2420 at 75mph) and I always felt like it was winding out a bit too high for me. With 5.13's on 37's I'll still get a very respectable crawl ratio of 91.93 and turn 2257 rpm at 75mph on the highway. So it seems like a decent compromise for a Bronco that sees quite a bit of both freeways and off-road.

Who knows, maybe I'll regret not going with the 5.38s. We shall see!

this is accurate, folks on FB did a gearswap that did require machine work with jeep gears. broncos gears have the bevel on the backside for FDU clearance IIRC. the real advantage of the "ultimate " spicer FDU is the huge axle shafts and the cast iron intermediate tube.

in the near future, someone will modify the oem FDU to accept the 32 spline diff and shafts, and bearing and seals.

the bigger CV axles and CV joints are impressive. 35 spline inner, with CV balls, race and cage the same size as race proven 934s!!!

 

[Darrell]

Great write up Dusty, you really hit this out of the park. I will be following your Youtube channel.

Thanks again

 

[Turbo yzel]

When can we get these axles in raptor form ?
I’ve called several manufacturers of the regular ones
And the answer is
Not enough man power or no current plans

 

[Dusty]

UPDATE: We just published an episode on the 5.13 gear install for our Horsin' Around YouTube channel. Please check it out

 

[Bird Dog Off Road]

UPDATE: We just published an episode on the 5.13 gear install for our Horsin' Around YouTube channel. Please check it out

Great video! Definitely doing this in the near future. Hope you guys will do a follow up posts/video a couple months out with how it's doing. I have 38s and am debating on 5:13s vs 5:38s for gearing.

 

[Dusty]

Great video! Definitely doing this in the near future. Hope you guys will do a follow up posts/video a couple months out with how it's doing. I have 38s and am debating on 5:13s vs 5:38s for gearing.

We'll definitely do some follow-up videos I'm already having "gear choice remorse" over not doing 5.38s but when I go back over my reasoning I still conclude that it was the sound choice for our use-case. With the Crawl gear in the manual transmission this thing was already a tractor even with 35's in 4-low (though slightly sluggish off-the line in normal first gear, 2-high, on the street). My final crawl ratio will be a bit deeper now even with the 37's so I think it will be just about right.

 

[Bird Dog Off Road]

We'll definitely do some follow-up videos I'm already having "gear choice remorse" over not doing 5.38s but when I go back over my reasoning I still conclude that it was the sound choice for our use-case. With the Crawl gear in the manual transmission this thing was already a tractor even with 35's in 4-low (though slightly sluggish off-the line in normal first gear, 2-high, on the street). My final crawl ratio will be a bit deeper now even with the 37's so I think it will be just about right.

Yeah, I have the Auto trans and I'm leaning towards 5:38s just in case I ever decide to go to 40s down the road.

 

[Dusty]

BTW I forgot to mention the Yukon Hard Core Diff Cover for the Bronco M220 rear diff in this thread. I figured I may as well beef that up too while I was at it. This thing is built like a brick $h&thouse out of cast nodular steel. My only complaint is I wish it had a drain plug.

 

[Aztec1382]

Great work
Interested in how they hold up
And if how you like the ratio you picked for 37s

 

[FstFrd00]

BTW I forgot to mention the Yukon Hard Core Diff Cover for the Bronco M220 rear diff in this thread. I figured I may as well beef that up too while I was at it. This thing is built like a brick $h&thouse out of cast nodular steel. My only complaint is I wish it had a drain plug.

Its a nice cover and was on my short list until I saw no drain plug

 

[Dusty]

Another piece of the puzzle showed up today. I hope they look nicer on the inside than they do on the outside, but the price was right

 

[Dusty]

A couple more pieces of the puzzle showed up this week.

 

[Dusty]

Well it's a few months later but I finally had the time and motivation (UBB) to get these axles swapped in, and I finished it up yesterday. I'll do a thorough writeup about it along with videos for our YouTube channel soon, but I wanted to let those who have been following this thread know that the deed has finally been done

I ended up just using the AUX switches since I was running out of time. I used switches #3 and #4 as they're 10-amp and #1 & #2 are 30- and 15-amp, respectively (rather save those for something that needs bigger draw). I read somewhere that the lockers only need a 10-amp circuit so hopefully that will work out OK. They do function correctly.

I also used the ProCal tune, really just for FAD delete. I'm not sure if I did it right, but I'm not getting any codes or other malfunctions. When I downloaded the tune to the ProCal unit, I was prompted with the question of whether I was installing any of the Ford Performance aftermarket FDU's. I technically was not, since it's a used factory M210, but I lied and told it I was, figuring that's what it wanted to hear, so I clicked the part number for the 5.13-geared one. It downloaded both the tune and some sort of DCLM -alphabet soup file. My best guess is that extra file is the re-write for the FAD delete. When I did the procedure to load the tune into the Bronco, there was no mention of FAD delete, or any prompting to do anything with that other file. Nor was there any mention of FAD anywhere in the settings in the ProCal unit. So I'm guessing it was just an automatic, invisible thing that it does if you tell it you bought the aftermarket FDU.

I still had a half tank of 87-octane (I'm a cheapskate) in it so my first trip was to the gas station was to put some high grade in it. The gas station in my little one-horse town only had 91 so I topped it off with that. So far no pre-detonation or any other problems I can tell.

In addition to the lower gears I simultaenously installed bigger tires. So I went from 35's on 4.46 gears to 37's on 5.13 gears (Nitto Recon Grapplers). That yielded a modestly lower final drive ratio than I had before, but that I thought would be better for my commutes than if I'd gone all the way down to 5.38. Since I did all this at once it's hard to judge what part of the "seat of the pants" difference is due to the tire and gear change versus the ProCal tune. But I do like it. It seems almost as peppy as it was in bone stock form with 30" tires on 4.46. Certainly better geared than the 35's on 4.46. I think the lower gears will come in handy off-road, even though it's not quite the tractor it would be had I gone to 5.38.

On Wednesday morning we're leaving for United By Bronco at Sand Hollow, Utah, so I hope to get at least a few easy break-in miles on it before then, though I know I won't be able to meet the conventional wisdom on break-in procedure. At any rate, I'll get some good seat time in it later this week so I can give a better reaction to the performance improvements.

Until then, if anyone has any questions feel free to ask.

 

[orion]

Nope, I broke down and got the Ford tuner to finally eliminate all FAD components.

So are you like @Snacktime and have to come to a complete stop to engage 4H?

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