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TeocaliMG

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Hey guys, here's a video I put together about the design and fabrication of a diff drop for my own Bronco. I suck at making short youtube videos, I always end up rambling on in detail but I think some of you on the forum are in to that.



I'll share pictures and write up as well for those who prefer to read. (all this is covered in the video)

For those who don’t, the primary goal of a diff drop is to reduce the CV angle at max rebound (max droop). Any spacer lift, or extended travel coil over will lower the rebound position of the wheel with respect to the differential and thus increase the CV angle. Strength of a CV joint is proportional to the operating angle, so even if a lift kit keeps the CV angle within an operational range with no binding, it still could have serious consequences for the strength. I went with ICON coil overs primarily to maximize my wheel travel which is why I am made this diff drop.

Before you go and just drop your differential, a couple things need to be considered.

1: Ground clearance. A well designed IFS system will maximize ground clearance between the wheels and that’s generally limited by the differential. See here how the differential protruced through the skidplate.
Ford Bronco Homemade Diff Drop for 6G Bronco 1709316477195


2: (more important) Plunge. Visualize the front suspension as a 2D model of a 4 bar linkage (frame, knuckle, and upper/lower control arms). The positioning of the inner and outer CV is critical for the axle to move freely and parallel to the suspension. Moving the differential downward misaligns the motion of the CV through suspension travel which means it will now plunge in and out more than intended. There is an allowable amount of plunge for a CV which again is tied to the angle. When the CV is straight it can plunge the most, in this case about 20mm in and out. When the CV is maxed out at 30°, the plunge is reduced to only about 10mm in and out.

I chose 20mm drop for my differential drop because that just about maximized the CV plunge I have available. If I were to drop further, 25mm or 30, even though the CV is at a lower angle, the plunge has exceeded the design limits and something in the system will be stressed excessively.

Here you can see the max CV angles in jounce and rebound for both the stock and icon equipped suspension. And for the standard differential position vs the 20mm drop position. Just putting on Icon suspension increased my max CV angle at full rebound by 50%! The 20mm diff drop reduces the max angle by over 3° or almost 12% reduced. Still not as good as stock, but a significant improvement vs where the ICONs were.

Ford Bronco Homemade Diff Drop for 6G Bronco 1709316656603


Ok, so now that I've established why I wanted a 20mm drop, I'll breakdown how I decided to achieve that.

The two main considerations I had when designing this diff drop were 1: strength/durability, and 2: ease of fabrication, specifically ease of fabricating it correctly. (dont want to do all this math and miss the mark.). With both of these in mind I came up with a relatively simple 2 piece design for the main bracket, where each peice could be relatively easily bend into the desired form. Bending 1/4" plate was more of a challenge than I anticipated. I first bought a cheap $50 vice break and shattered that. So, I coughed up the cash for a much beefier (and pricier) break, under the justification that I will use it for decades to come. This could have been avoided by fabricating more smaller pieces and welding them into form, but that was at least a partial compromise to my 2 most important considerations listed above.

Even with my relatively simple design, getting precise bends was a challenge. My first attempt was too far off the mark, on my second attempt I made little plastic guides to help align the break exactly before bending (3D printed green).
Ford Bronco Homemade Diff Drop for 6G Bronco 1709317001010
Ford Bronco Homemade Diff Drop for 6G Bronco 1709317040661
Ford Bronco Homemade Diff Drop for 6G Bronco 1709317067460


Welding up the parts was rather easy. First, I used a 3D printed gauge to check that the bent parts held position of the holes correctly as well as the width of the flanges. I also used this gauge to hold everything in place for spot welding the parts together.

Ford Bronco Homemade Diff Drop for 6G Bronco 1709317236113
Ford Bronco Homemade Diff Drop for 6G Bronco 1709317256542
Ford Bronco Homemade Diff Drop for 6G Bronco 1709317284592


Here's the bracket welded up prior to painting:

Ford Bronco Homemade Diff Drop for 6G Bronco 1709317322804
Ford Bronco Homemade Diff Drop for 6G Bronco 1709317344937
Ford Bronco Homemade Diff Drop for 6G Bronco 1709317363920


Here it is side by side with the OEM bracket, as well as the two less interesting but equally important parts of the kit:
Ford Bronco Homemade Diff Drop for 6G Bronco 1709317462126
Ford Bronco Homemade Diff Drop for 6G Bronco 1709317588348


Fully Installed:
Ford Bronco Homemade Diff Drop for 6G Bronco 1709317664659
Ford Bronco Homemade Diff Drop for 6G Bronco 1709317913950

Ford Bronco Homemade Diff Drop for 6G Bronco 1709318032264


----------------------------------------------------------------

Update: Regarding customization of the skidplate. The OEM badlands skid plate has only 4 bolts holding it in, In these photos, you may notice that there are 5, and later the bolt which used the OEM diff bracket was removed.

This middle bolt is using an otherwise unused weldnut available right next to the diff bracket. I had previously modified my skidplate to use that additional weldnut per the install instructions for the Lobo hidden winch skidplate. I later forgot that that was a modification I made and thus forgot to mention it here.

If you modify your OEM skid plate with this diff drop, and lose the mounting attachment there, you will definitely want to modify your skid to accept a bolt in the unused hole next to the diff bracket.

From Lobo:
Ford Bronco Homemade Diff Drop for 6G Bronco 1712073705685-xw


My modified skid with new hole:
Ford Bronco Homemade Diff Drop for 6G Bronco 1712073770171-1o
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PWillette

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Holy shit man...nice work!
 

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Nice work. You’re calling it a kit… Does that mean you’re making more? Definitely something I plan to do later.
 

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TeocaliMG

TeocaliMG

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Nice work. You’re calling it a kit… Does that mean you’re making more? Definitely something I plan to do later.
I've considered it. It's not hard to design but I know not everyone has the tools to cut the patterns, let alone bend it. But if there was enough interest I would do it, but I would also get a little CNC plasma cutter to cut the plates. Much more appropriate than using the tormach just for cutting out 2D patterns. Something thats on my shopping list already for another project.
 
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TeocaliMG

TeocaliMG

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I’ll take a 1/2” kit in American size thanks! I don’t know what the mm equivalent is 😂

Seriously good work!
25.4mm=1 inch. 20mm is about 0.8". I might be able to push it all the way to an inch, but I wanted to account for the plunge, plus variability with alignment (not bottoming out because of where the control arms are pinned down.

If you have adjustable UCA's you could run more drop, this is because you really only hit the plunge limit in compression of the CV (rebound) and if you could adjust your alignment outward more you could bias the plunge range to accept a drop lower than an inch. Also, aftermarket CV's like RCV's might have more plunge but I have no idea.
 
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TeocaliMG

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I dig it. If you don't want to make and sell these you could check out Send Cut Send they support drop shipping.

(86) [ModCrate DIY] How to Produce your Own License Plate Frame | Bronco6G - 2021+ Ford Bronco & Bronco Raptor Forum, News, Blog & Owners Community
Thats a great idea, i've heard of send cut send but never considered it for dropshipping. Now I just have to decide how badly I want a CNC plasma cutter for myself lol


I'm also working on a little 1/4" plate bash guard/ramp for that sharp notch on the front of the diff. But honestly, I may just use the cutoff wheel and chamfer it off since its probably just a remnant from the manufacturing.

Ford Bronco Homemade Diff Drop for 6G Bronco 1709326668364
Ford Bronco Homemade Diff Drop for 6G Bronco 1709326700197
 
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I use my friends shop all the time, nice 5'x10' plasma table and DMG4100 mill. Have to say I prefer SCS as I don't have to clean up dross on the plasma cut parts. Checking out your site, wish you had a hard top, I think you could come up with some cool attachments for the hardtop mounts I make.

Protocase and OshCut are some resources you might also find useful.

Open door if you ever want to talk shop
 
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TeocaliMG

TeocaliMG

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I use my friends shop all the time, nice 5'x10' plasma table and DMG4100 mill. Have to say I prefer SCS as I don't have to clean up dross on the plasma cut parts. Checking out your site, wish you had a hard top, I think you could come up with some cool attachments for the hardtop mounts I make.

Protocase and OshCut are some resources you might also find useful.

Open door if you ever want to talk shop
Just checked it out, and I agree! So far, my (limited) products are based simply on things I wanted lol. Not great at coming up with stuff out of the blue unless it's solving a problem for myself first.
 

Brian_B

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That looks awesome. I love homemade mods
 

5GENIDN

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I’ll take a 1/2” kit in American size thanks! I don’t know what the mm equivalent is 😂

Seriously good work!
You may want a 3/4 inch if you want the same drop.

Edit: oops already addressed....
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