Rear diff question

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Hello I have a 72 dart swinger with a 360 and 727 it has a 7 1/4 rear diff and my ex father in law just gave me a Ford 8" diff out of an old falcon, I know I will have to fab some stuff like relocating the spring pads and possibly the drive shaft. So I was wondering if anyone had any input on this? The 8" diff is 4 inches shorter over all and the spring pads will have to be moved out 2" on each side.

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HI It sounds like you have a very mild motor , by the time you cut your housing if you can do that and buy shorter axles or have your axle shorten for a ford 9'' good strong rear if your building a full track car. You can buy a 8 1/4 posi rear that will be good for 375 hp cheep . have picked them up for $350 there a a lot of these around or 8 3/4 rear there are some guys out there that don't want your arm and leg four them but they are at swap meets most of the time , this rear will be good for at least 800hp and more . I have picked up a body housings for as little as $150.00 and 849 posi housing for $ for $175 to $350 yes would put a bearing kit in them , And a body axles for$ 50 a pair to $ 100.00 . but this takes some looking around . Hope this is of some help to you
 
Yeah I wouldn't do all that work for a Ford 8". A Ford 9" or 8.8 maybe. You mean the 8" housing is 4" narrower? I wouldn't do that either unless you're planning a mini-tub, you'd need negative offset wheels to keep the tires off the springs if the backspace has to change by 2" per side.

I'd be looking for a 8.25", or even an 8 3/4 out of a 65-67 or 68-70 B body. Or yeah, a Ford 8.8 or 9". You're going to have to relocate perches and shorten the driveshaft anyway, might as well do it for something worthwhile.
 
Just searched a bit and found it has 28 spline axles, can get many gears, locking differential and disc brakes.

I like the idea, I like free too.
 
Here's a thread on the 8.8 swap. Well, this is the stickied thread. There are a ton of them on there though 8.8 swap

The 8.8 out of the explorer's are offset, so, typically what is done is the side with the long tube is cut down to match the short side. That way you get a centered diff and you can still use factory 8.8 axles, you just get two from the same side (shorter side). And you only have to shorten one end. Even if you have to pay to have the housing narrowed it's only one side, and the cost of the 8.8 core compared to almost any of the stock mopar stuff would mean you'd still probably spend less money. There should be quite a few members that can answer questions about that swap too. I looked into it but I have a Duster (wider quarters in the back) so I just used a B-body 8 3/4, which cost half as much as their A-body counterparts.
 
Hello I have a 72 dart swinger with a 360 and 727 it has a 7 1/4 rear diff and my ex father in law just gave me a Ford 8" diff out of an old falcon, I know I will have to fab some stuff like relocating the spring pads and possibly the drive shaft. So I was wondering if anyone had any input on this? The 8" diff is 4 inches shorter over all and the spring pads will have to be moved out 2" on each side.

View attachment 1715043001
I forgot to mention he also gave me a-body spring relocation brackets
 
Much like the Mopar 8 1/4, the Ford 8" is a lot stronger than people give it credit for. But, axle availability is not good, unless you go custom like Moser, Strange or Currie. Keep in mind it has three pinion bearings, much the same as a 9" and that gives it some strength.

Lastly, if you find the ribbed center section, it is very strong. I have one in the 8" housing under my Mercury Bobcat.

Here is the heavy duty extra ribbed 8" center section. A lot of people don't even realize Ford ever made one, but they did.

HEAVY DUTY 8 INCH.jpg
 
HI It sounds like you have a very mild motor , by the time you cut your housing if you can do that and buy shorter axles or have your axle shorten for a ford 9'' good strong rear if your building a full track car. You can buy a 8 1/4 posi rear that will be good for 375 hp cheep . have picked them up for $350 there a a lot of these around or 8 3/4 rear there are some guys out there that don't want your arm and leg four them but they are at swap meets most of the time , this rear will be good for at least 800hp and more . I have picked up a body housings for as little as $150.00 and 849 posi housing for $ for $175 to $350 yes would put a bearing kit in them , And a body axles for$ 50 a pair to $ 100.00 . but this takes some looking around . Hope this is of some help to you
There isn't a lot in my area for mopar and what there is is super expensive and I'm on a budget
 
Much like the Mopar 8 1/4, the Ford 8" is a lot stronger than people give it credit for. But, axle availability is not good, unless you go custom like Moser, Strange or Currie. Keep in mind it has three pinion bearings, much the same as a 9" and that gives it some strength.

Lastly, if you find the ribbed center section, it is very strong. I have one in the 8" housing under my Mercury Bobcat.

Here is the heavy duty extra ribbed 8" center section. A lot of people don't even realize Ford ever made one, but they did.

View attachment 1715043229
It's all free including the wheels and tires to start with the only thing
There isn't a lot in my area for mopar and what there is is super expensive and I'm on a budget
My biggest reason to swap right now is for slightly stronger than the 7.25 and for the 5x4.5 bolt pattern it's basically all free the rear diff, the spring relocation mounts, the wheels and tires, and his help, garage, tools, and knowledge. The only thing that I have to pay for used the front rotors and pads for a 73 dart swinger and with all the input from you guys and what I've read elsewhere it seems like it will be fine for a start thank you all for the input
 
I forgot to mention he also gave me a-body spring relocation brackets

A full 3" relocation? That's a lot of work to do right, and if you're not going to mini-tub the car there isn't any point in doing it. You can get the same tire clearance with a bolt in 1/2" spring offset hangers/shackles. Doing the 3" relocation and mini-tub will be a lot of welding. If that's what you want to do great, but I'm just pointing out that doing a full 3" spring relocation and mini-tub is a lot more involved than just moving the perches and bolting in an axle.

Much like the Mopar 8 1/4, the Ford 8" is a lot stronger than people give it credit for. But, axle availability is not good, unless you go custom like Moser, Strange or Currie. Keep in mind it has three pinion bearings, much the same as a 9" and that gives it some strength.

Lastly, if you find the ribbed center section, it is very strong. I have one in the 8" housing under my Mercury Bobcat.

Here is the heavy duty extra ribbed 8" center section. A lot of people don't even realize Ford ever made one, but they did.

View attachment 1715043229

Yeah I would avoid the 8" not because of strength, but because of parts. And yeah, if it is 4" shorter it wouldn't work well with the stock spring locations. And if I was going to run a 3" relocation and mini-tubs to clear some wide sticky tires I wouldn't want the 8" because you'd probably want better axles to do that, and those would need to be custom, so, more expenses.

"Free" always sounds great, but if it takes twice much work to use the "free" part it might still not be worth it.
 
Is the 7 1/4 a really weak unit? If you are on a budget, why not try to break it? You could still put the spring relocation kit on to prep for wider wheels while saving a few bucks or sell the falcon diff. I dont see any traction on your ride right now. I think its a cool car for sure! I personally like the challenge of breaking ****. If you cant break it, no need to swap it. Do the 7 1/4 have the "lunchbox locker" available? Really cool car though. Has that Mad Max look, especially with the Arizona background.
 
Oh I just read the part about wanting a different bolt pattern.....now I know why you want the swap. got it...a little slow over here.
 
Is the 7 1/4 a really weak unit? If you are on a budget, why not try to break it? You could still put the spring relocation kit on to prep for wider wheels while saving a few bucks or sell the falcon diff. I dont see any traction on your ride right now. I think its a cool car for sure! I personally like the challenge of breaking ****. If you cant break it, no need to swap it. Do the 7 1/4 have the "lunchbox locker" available? Really cool car though. Has that Mad Max look, especially with the Arizona background.
That is in oatman as lol
 
My dad has broken a couple axles in his 8" rear in his 65 ranchero. Considering how light the car is as and the lack of weight over the rear, that shows how weak they are. I wouldn't use an 8" rear in an A body mopar if it was given to me. In my opinion, you're better off selling it and finding an 8-1/4, 8.8, etc.
 
IIRC
At 4 inches narrower, and with the springs relocated, the housing will be too narrow to put the perches in the correct location. One U-bolt on each side would be on the bearing housing, and that won't fly. You would have to suck the springs towards the centerline, to make it work; and I cannot imagine what that might do to the bushing life, or the handling.

To fill the wheelwells up, you will want about 8.5 inch rims with about a 4 inch backspace.I'm guessing a little there.
 
See all this talk about cutting and shorting , Didn't rear all posts but am i missing something are you tubing the car . you can get a 245/60 14'' under the car no trouble or a 15'' on a rally wheel .You can get other wheels and go 265/ But here what i am getting at 1971 to 1976 darts / dusters /sport darts all could be gotten with the 8 1/4 rear this would be the same with as you rear now NO CUTTING and after 72 were 4.5 bolt patt. if you still wanted more tire under car WITH out cutting the housing and replacing the axles just do the spring relocate . or 71 to 72 and just find a pair of later axles from a body 4.5
 
So I went to do the swap today and with some closer measurements it is the same width from back plate to back plate but the perches would have to be moved out 2" on each side and I would have to have the driveline shop here in town make a custom $50 u joint so I decided to sell this diff and buy this 73 dart for the 83/4 and front spindles because my dart has disc brakes with 4 piston calipers and small 5x4 bolt pattern and I can't find rotors little lone to fit with 5x4.5 bolt pattern. But thank you all for your input here are some photos of the 8" diff
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The narrowest of the 8" rearends that I have researched is 56". An A Body is 57 1/8" wide with 43" spring perches. I have seen that 56" 8" Ford swap, it was pretty much a drop in, except for the driveline. 66-67 Mustangs had a 57 1/4" wide diff in them with 43" perches as did early Mustang IIs, if ya like 4 bolt wheels like the Mustang IIs. I flogged the 8" in my 66 Ranchero unmercifully and never hurt it. Where in the world did a 53" wide 8" come from? I'm going the 9" direction myself. It's about the same width as the short B Body rearends. Spring perches are 44" centers, but the register hole in them is about an 1" in diameter, I think the spring contact area can be modified to put the centerbolt in the correct place with very little effort. The shock plates are the big question. The OE holes are on 3" centers and just guessing the 3" tubes on the 9" will require about a 3 1/2" centers. I have the technology to weld the holes in and redrill them. Anything I'm missing? 8 3/4s are great rearends, but way too many of them found their way to the smelters in a foriegn land better left unspoken.
 
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