B-Body 8.75 in a 72 Duster?

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Fuzz

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Hi all! Need a new rear end to replace my 7.25 now that I've managed myself a 340. My question is what 8.75 rear ends will fit in my 72 Duster? I'm not too familiar, I've read the guides on axle length and all but does that just mean the tires would stick out a little more?

There's a 742 (no idea ratio or suregrip yet, have to ask seller) that's wheel to wheel for $300 on Craigslist near me, owner says it came out of either a 67 or 68 Charger. Would that bolt in or would it be too big? I've heard that some earlier B body rear ends fit nicely in the Dusters/ Demons.

Thanks in advance!
 
yep, you are correct. Done this. We just oval the eye holes about 1/4 inch and drop it in.
 
66/67 B body is a drop in.

68-70 is noticeably wider.

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I've read the guides on axle length and all but does that just mean the tires would stick out a little more?

You can correct that with deeper backspacing on the wheels.

I put a B body rear in my Dart Sport, with 5 1/2 inch backspace. It fit's rather nicely.

Paved Road Shot2.JPG
 
NONE of the B body rear axles are a "drop in" operation.

The 62-70 B body housings all have spring perches at 44" center to center, vs 43" for an A-body rear axle. That means you need to move the spring perches. If you don't, you will put a bind on the springs and bushings. That will wear out your spring eye and shackle bushings prematurely, and the bind keeps the rear suspension from operating smoothly and doing its job properly. Do people take shortcuts? Absolutely. But that's what they are- shortcuts that hurt handling performance.

As for the widths, it depends on what you're doing for wheels and tires. An A-body 8 3/4 using BBP axles is about 57 13/16" wide at the wheel mounting surfaces. A 65-67 B-body 8 3/4 is 59 1/2", a 68-70 is 60 1/8". On a Duster/Demon/Dart Sport if you want to run a 15x8" and center it in the wheel house with an A-body 8 3/4 and BBP axles you want about 4.5" of backspace. So, if you use a 65-67 B 8 3/4 you'd want more like 5.3" of backspace on a 15x8 to keep the wheel in the same place. Use a 68-70 B-body rear axle and it would be more like 5.6".

I have a 68-70 B body 8 3/4 in my Duster. When I was still running 15x7" cop wheels with a 4.25" backspace the widest tire that would still fit was a 225/60/15, and that was pretty close to rubbing. In a 15x8 it's usually pretty easy to find rims with 4.5" to 5" of backspace, finding them with 5.5" or more is usually a little harder, but not impossible. Just fewer style options for off the shelf wheels. Now, if you use 17" or 18" diameter wheels it's easier to find them with deeper backspaces.
 
I had a 67 charger 8 3/4 in my Barracuda. I had the offset shackles and fit well with offset rims. Depending on what engine setup you have you can use an 8 1/4 will hold up and be a lot less and bolt right in.
 
I had a 67 charger 8 3/4 in my Barracuda. I had the offset shackles and fit well with offset rims. Depending on what engine setup you have you can use an 8 1/4 will hold up and be a lot less and bolt right in.
I have a 340 out of a 73 Challenger!
 
put a b body ('66) 8 3/4 in my '70 duster with no mods at all. running 14" ralley wheels.

Just wedged those leaf springs over a half inch and called it good huh?

Not worried about losing tire clearance or the rear suspension binding up I guess. Oh well.
 
No issues with wear or bind in over three years.

67 axle from Coronet in 73 Duster.

factory 15x6.5 rallye wheels

no mods to anything but driveshaft

looked and drove like it was supposed to be built that way
 
No issues with wear or bind in over three years.

67 axle from Coronet in 73 Duster.

factory 15x6.5 rallye wheels

no mods to anything but driveshaft

looked and drove like it was supposed to be built that way
Yep, the one we put under a '72 Duster about 18 years ago is still there. We did oval the eye holes about 1/4 inch in per side.

Again NO issues.....
 
No issues with wear or bind in over three years.

67 axle from Coronet in 73 Duster.

factory 15x6.5 rallye wheels

no mods to anything but driveshaft

looked and drove like it was supposed to be built that way

Yep, the one we put under a '72 Duster about 18 years ago is still there. We did oval the eye holes about 1/4 inch in per side.

Again NO issues.....

You mean “no issues that you noticed”. Which says more about both of you than it does the suspension.

There IS a difference. If either of you bothered to check the suspension movement before and after your little shade tree short cut you’d have noticed the binding. The fact that you didn’t notice doesn’t mean that there isn’t a difference, it just means you don’t know what it should actually feel like when the suspension is truly working properly. In stock trim these cars handle like barges, so I suppose I shouldn’t be surprised people think that’s normal.

Tuning suspension is just like anything else. Little things add up and make a difference. Like port matching an intake manifold. Is it a “holy crap that’s amazing!” kind of difference all by itself? No, it isn’t. But it does make a difference, and when you start adding up those little differences you end up with a car that you can tell was “done right”. Or one you can tell wasn’t.
 
You mean “no issues that you noticed”. Which says more about both of you than it does the suspension.

There IS a difference. If either of you bothered to check the suspension movement before and after your little shade tree short cut you’d have noticed the binding. The fact that you didn’t notice doesn’t mean that there isn’t a difference, it just means you don’t know what it should actually feel like when the suspension is truly working properly.

LOL.... Ummm……. your responses lately says more about you than it does the suspension as well. Read what you right, then take a chill pill and re-read it.

The op asked a question, and we answered it as well as you. We all gave our opinions and experiences. He'll decide for himself. And to the op, I have a B-body rear end myself that i'm going to drop in in place of a 7.25. And I was so happy with the way they turn out by 1/4 inch oval of the perch, it's the way I'm doing it again.
 
I didn't elongate anything either.

1/2 inch per side is pretty close to the factory tolerance, judging by how off center I've seen some.
 
LOL.... Ummm……. your responses lately says more about you than it does the suspension as well. Read what you right, then take a chill pill and re-read it.

The op asked a question, and we answered it as well as you. We all gave our opinions and experiences. He'll decide for himself. And to the op, I have a B-body rear end myself that i'm going to drop in in place of a 7.25. And I was so happy with the way they turn out by 1/4 inch oval of the perch, it's the way I'm doing it again.

I do read what I write, perhaps you should too. I considered what I said this time pretty carefully because I've argued against people taking lazy shortcuts on perch locations before. It's obvious you just slapped those leaf springs on without checking for any binding in the spring action compared to leaf springs mounted properly. Your springs aren't working at their best, period. If that lazy shade tree operation is good enough for you, awesome. But just because you don't know the difference doesn't mean there isn't one, and telling other people your lazy shortcuts work just as well as doing it right is total BS.

I have put a 1/4" worth of bind on the leaf springs on my car when I was using those poorly designed " 3/4" " Mopar Performance offset hangers and shackles that use a 1/2" offset hanger and a 3/4" offset shackle. It's noticeable on install, and it's noticeable in the spring action if you bother to check for it. I did, and I got rid of that binding when I switched to spring sliders and lined everything back up. It makes a difference. Do all kinds of people run with that bind? Yes. It just means none of their leaf springs are working as designed. Given that most of these cars are infrequently driven and poorly set up, it's not a surprise that people don't notice or write it off as it being normal on an old car. Doesn't make it right.

I didn't elongate anything either.

1/2 inch per side is pretty close to the factory tolerance, judging by how off center I've seen some.

Not on the axle perches it isn't.

Yes, it is fairly common for the axles to not be perfectly centered to the body. But that's almost always because of body tolerances, not axle tolerances. All the factory axle perch widths I've measured have been within an 1/8", and I've measured dozens. Most are exactly at the factory specs. Wheel housings and quarter panels on the other hand are frequently off by a 1/4" or more, and if an axle isn't centered to the body it's usually because the body is off. And that's not the frame rails either, the axles are usually well centered to the rails. The body tolerances are all over the place, and people notice that because of tire clearance issues. But that's a totally different issue.

Dropping an axle with the perches at 44" c-c and spreading the leaf springs out a 1/2" per side because they're mounted at 43" c-c isn't anything close to the factory tolerance.
 
If that lazy shade tree operation is good enough for you, awesome. But just because you don't know the difference doesn't mean there isn't one, and telling other people your lazy shortcuts work just as well as doing it right is total BS.

  • Ok, I'm lazy, I take shortcuts, and I don't know the difference, and I spread garbage! :D However, I never insulted you once (nor did I comment on your method). But I'll stand out of your way and let you put on a vulgar display of ignorance. Carry on !!! and..... So Long !!
:lol:
 
I have a Bbody rear end in my 72 dart, I put it in more than 20 years ago. When I installed it, I just pulled the springs apart to fit the perch width. Over time both mounting brackets for the spring shackles were twisted, and actually started to separate from the frame. I have since realigned, and reinforced the shackle mounting brackets. I also moved the perches in on the rear end to A body specs. Not saying anyone is wrong, just saying what happened to my car when I inadvertently put too much stress on the shackle mounts.
 
I have a Bbody rear end in my 72 dart, I put it in more than 20 years ago. When I installed it, I just pulled the springs apart to fit the perch width. Over time both mounting brackets for the spring shackles were twisted, and actually started to separate from the frame. I have since realigned, and reinforced the shackle mounting brackets. I also moved the perches in on the rear end to A body specs. Not saying anyone is wrong, just saying what happened to my car when I inadvertently put too much stress on the shackle mounts.
I can see that happening. That's why I oval the perch holes about 1/4 or more in each, to give it relief.
 
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