B-Body 8 3/4 Rear End in an A-Body

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MuuMuu101

MuuMuu101

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Good afternoon guys. So I've been debating about putting a B-Body 8 3/4 into my 68 Dart in the future. The A-Body ones I see are generally either too far or too expensive. I currently have an open 7 1/4 with 2.91 that was running fine when my car was running, but I'd like something that will probably kick it up a notch. I was thinking about something around a 3.23 to 3.55 gear ratio with a 25-26" tall tire. I was running with a stock 273 and 904 trans but hope to do a 340 or 360 engine swap sometime within the next year or two. I do plan on making the car more of a handling car. I have the KH disc brakes and 10" drums in the back with stock steel wheels all the way around. I was hoping, after the rear swap to throw on some 17 x 7 or 8" wheels with 4.25" and 4.5" backspace respectively. They make them in both sbp and lpb so I don't really have a problem. I know I won't be able to get too wide of a tire on there, but I was hoping for around 225/45/17" tires on the front and 245/45/17's on the rear for now till I can get better wheels.

Ok now that I've talked about my plans I can ask my question. Since bolt pattern doesn't really matter, how wide of a B-Body rear end can I go? I know the 65-67 rear ends are about 2.375" wider and the 68-70's are 3" wider. Is the 68-70 too wide? I also found a local 8 3/4 rear end from a 64 B-Body for $150 but I'm guessing that may be a little too wide for my Dart (3.75" wider). Also is there anything else that would be needed to do the swap besides changing the driveshaft length and relocating the springs 1" inboard? Thanks for all your help and have a great day!

Edit: Also found an A-body 8 3/4 drum to drum on CL for $500 not too far away. Maybe I should snatch that?
 
I think you answered your own question, jump on that A body 8 3/4. That's a good price.

The B body rears are going to need to be shortened or will need more backspacing to fit your wheels in there.
 
ESP47 said:
I think you answered your own question, jump on that A body 8 3/4. That's a good price.

The B body rears are going to need to be shortened or will need more backspacing to fit your wheels in there.
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Just called the guy. It's an open 2.76. I'm going to see it on Saturday morning. What things should I look for? From what I understand there's an early one and a late one and the distribution T for the brake lines may be placed in a different location.
 
Just make sure it doesn't have a center nut in the center of the axle.
 
Any other suggestions before I stop by tomorrow morning? Thank you!
 
The B will fit, but you will need deeper backspacing on the wheels. By the time you buy the rear and wheels you may just as well get the A body rear. 500 is a decent price. I see them around here upwards of 1000 bucks, and sometimes more.
 
The B rear swap is much better solution for a Duster or even a Barracuda than a Dart/Scamp/Valiant. The Duster's larger wheelhouses make it a much easier fit, even with the increased backspace rims. The stock A body width matches the Darts much better, its actually kind of short for the Duster.

If you did do a B rear swap on a Dart the '65-67 B would be a better choice than the 68-70. The width on the 68-70, and the backspace needed on the rims would make changing the wheels a pain in the butt.

I'm going to swap a '68-70 B rear onto my Duster so I can run modern 17 or 18" rims and run the same backspacing as up front, but I wouldn't do it on my Darts.
 
Just talked to the guy again on the A-Body diff. He said it's a 489 case with sbp and he believes the brake lines are intact; however, he does want near asking price money for it.
 
MuuMuu101 said:
Just talked to the guy again on the A-Body diff. He said it's a 489 case with sbp and he believes the brake lines are intact; however, he does want near asking price money for it.
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1970Duster said:
And you haven't bought it yet, why?
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Exactly!!!

$500 is a good price to begin with. The sell for more, especially with 489's. And unless they have aftermarket axles, all a-body 8 3/4's are SBP.
 
There are a few within driving range of me. Cheapest is $750. The other two are $1000 ea with a note - no discounts on them. I think $500 is fair and if I was closer I'd already own it.
 
I bought it... Update is on my project thread. It's a good diff for a good price. :D
 
72bluNblu said:
The B rear swap is much better solution for a Duster or even a Barracuda than a Dart/Scamp/Valiant. The Duster's larger wheelhouses make it a much easier fit, even with the increased backspace rims. The stock A body width matches the Darts much better, its actually kind of short for the Duster.

If you did do a B rear swap on a Dart the '65-67 B would be a better choice than the 68-70. The width on the 68-70, and the backspace needed on the rims would make changing the wheels a pain in the butt.

I'm going to swap a '68-70 B rear onto my Duster so I can run modern 17 or 18" rims and run the same backspacing as up front, but I wouldn't do it on my Darts.
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I too wondered about this, i have a 71 Duster i just hauled back to the house to fix up. I got a lead on a b-body 8 3/4 rear with sure grip for a decent price and wondered how it will fit my duster. Thanks for the info..
 
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