So I've been reading around a bit on rear end swaps and all, and I've been wondering something.
How does one figure out which rear end would make a good candidate to swap into a car? How do you decide what's going to work out and fit and what won't?
I think it would be some interesting research, once I know what key points there are to look for, to see just how many different rear ends you can pull off cars to swap in for the different gear rations, disc brake conversions, etc., and compile them all.
Can anybody explain it to me please?

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

Your critical dimensions are the distance between the brake sheilds/axle flanges (this is kind of the 'overall length'), the distance to the outside of the drums or discs (this will determine what kind of wheels are needed/ what kind of offset to make it work), also the distance between the centerline of the leaf spring pads if just doing a straight swap between models *or* if needing to cut the old suspension mounting parts off the axle and weld on spring pads to work with your existing leaf spring set up... (another good measurement is the pinion position so someone swapping will know how much shorter they need to cut down their driveline)...

Lets use an old style 'hack' that's widely known (and I'm not going to get totally specific (you can change studs/ brake shoe widths, etc... to get the desired effect if trying to get something to work...):

A 1962-1972 A-body 7 1/4" rear axle is 53.2" axle flange to axle flange, the spring perches center to center are 43" and the centerline of the axle shafts to the centerline of the rear u-joint is about 10"...

Suddenly uncle joe stops by with an 8 3/4" rear out of a 1968 Dodge Charger to donate to you... he says, just use a pry bar and spread the leafs out another inch and it'll swap right in....but you decide to check the measurements and remount the perches and see if the width is going to allow you to still mount those 215/70R14's under your car....

8 3/4" B-body rear for 1962-1970 is 55" axle flange to axle flange, 44" between the centers fo the perches, and 12.35" center of u-joint to axle shaft center....

So you'll need to remove 2"+ inches from the driveline, the perches need to move outward another 1/2" each (so maybe getting some big guys to reef down on the u-bolts isn't such a bad thing)... and the brakes at 2" or so each plus the 55" is about 59" over the A-body 53" + 4" (or so), at 57"... so if you don't have the tight wheel wells that some of the 4 doors have or down size the width of the tread, or change the offset of the wheel if using some 'fat' tread, you can get away with your 'stock' tires on that swap....

(so if you can come up with an axle that with the disc brakes is as long as the drum axle face to face, and remount the perches, you are in good shape...)

-D.Idiot

On any potential swap (rear axle, transmission, engine) I look at the interface points.

Where does my swap item interface with the vehicle?

On Robs rear swap the interfaces are: spring perches, wheels, driveshaft, body sheet metal , brake lines, ebrake.

On a 5 speed trans : trans mount , floor hump, clutch linkage, bell housing, pilot bushing.


By focussing on the interface points and making a chart of all the interface measurements on BOTH the car and donor you can make decisions as to fit and price.

Research is fun and very inexpensive. Share what you find.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Thanks you guys!! Once the weather gets a bit steadier I'll probably be spending some time in junkyards with a measuring tape and a notebook.. a friend of mine who builds/races Fords gave me some tips he learned from the Ford guys pertaining to rear end swaps, so I thought I'd look into them and see how well they translate over to us. It'll be a while, but I'll let you know what I find as I find it.

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

I did the 8.8 swap which was better for my needs as the next engine going in a reasonable amount of time will oush the envelope. However, after doing the swap and fighting with perches and such this is my suggestion...
An 8 1/4 have been cheaply built to handle a healthy 360 if you look around the internet. Get a drop in unit for not a ton of money and don't fight welding perches. The strength shouldn't be an issue any time soon for ya Steph. If you got anymore questions of thoughts bounce them off us.
So to answer your question from the first post you just need to know hub-to-hub distances on what is close enough and what to cut. Than the costs of the unit or amount to adapt it, and last should be the worries of strength.

well how big are you goin to build this motor, ive only been through one 7-1/4 in my super six slant in the decade ive owned and abused the crap outta it...
and what is your income... you got the money go for it...

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder

I haven't completely decided on where I'm going yet, still need to see for sure whether I'm going to be commuting/what's going on..
I originally asked just to see what different rear disc options there are out there. But it would be nice to compile some sort of data that way when people are looking for different combinations of things, they can check out a list and go hey, that car has what I need.
I know there are a few different standards to swap, but I can't imagine they're the only choices available.

Your friendly neighbourhood research geek,

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

My personal opinion, is the rear disc option should be the least important item, to consider. On an "A" body car rear disc will not be a "Major" improvement over 10 inch drums, and do add another level of cost and difficulty, to the swap.
Also as previously stated, don't get rid of a 7 1/4 rear that is still good, "just because". If it is in good condition, it will take a lot more abuse then it is given credit for (especially if it is a SG (rare)). I have a 7 1/4 SG in my 13 sec drag car.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

As far as the rear disc option thing, you can see the thread I started on that --> http://www.slantsix.org/forum/viewtopic ... sc&start=0. I'd rather not discuss it here.

Whether I'm swapping things out or not, doesn't matter. I'm still going to look into things just as options, for myself in the future, my friends who are building slants around here, and hopefully anybody on the board who wants/needs the information.
I think a compilation of these things would be good.
I know a lot of people on this board have full time jobs, families, houses, and their projects.. doesn't leave a lot of time to go to the junkyard just to look. I have that time, and since I don't have any money to put into my car right now, I may as well take the extra time and go look around, see what's out there for us. It'll keep me busy, doing something I enjoy, and hopefully I can contribute something useful to the site.
That's the whole reason I started this particular thread.

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

I'm really happy with the 8 3/4 sbp rear end I found. It was $300 bucks and bolts in. I can get discs for it now without changing the bolt pattern which is nice because I've got the K-H front discs. My suspicion is that if you can find a 8 3/4 a-body rear end and the K-H discs you've got yourself a cheaper set up than a lot of other options and a hell of a lot easier to bolt up for an amateur wrench like me. The 8 3/4 a-body rear end is not common but it's also not unobtanium and has the great advantage of a easily changeable rear end.

If you find these parts and need a set of 14" steelies with good Eagle GT tires let me know. I've got a set with less than 7500 miles but I'm going to use a set of the Coy's sbp wheels when I get home in September. Since it sounds like your going to take your time and figure things out that may work for you. I highly recommend a copy of Tom Condran's "Performance Handling for Classic Mopars". He does a great job of debunking some myths and comparing the different systems available from the junkyard. He tends to stick to the Mopar stuff and he doesn't go into all the exotic rear end selections that people here have used but it's a jem and easy to read. It will also help you with your brake options. Just my two cents...

-Ned Lange

you got hooked up if you got that axle for 300$, i might get just the third member for that, and im gettin hooked up... sigh

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder

What are you looking for? I got a 489 case 3.55 pumpkin for $150 (before tax), and the same place had a couple of other 489 case pumpkins for $100, one was a 3.23 (I think). I also saw a 742 case on the floor with a 2.79 gear in it, don't remember if I asked what they wanted for it though.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car