Will the rear axle fit?

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74 dart sport

Kameron
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Does anyone know if a 8 and 3/4 rear axle from a 1968 B- body would fit in a 1974 dodge dart sport originally with a 8 and 1/4 rear axle (A- body)? The 8 and 3/4 axle is a 3.23 sure grip and the 8 and 1/4 axle is a 2.76 peg leg. Would I be able to just swap out the two? Are the measurements the same?
Thanks, Kameron
 
Are you talking about the complete housing...brake drum to brake drum?
 
The spring purches on the B body is 44" where a A body is 43, close but not going to work
 
They're not the same size, but a '68 B-body 8 3/4 will work in a Dart Sport or Duster body. I have a 68-70 B body 8 3/4 in my Duster. You do have to move the perches, the B body perches are at 44" c-c and will need to be moved to 43" c-c. I moved mine to 42" c-c and installed a 1/2" spring offset kit, figured if I had to move them I might as well gain some room for tires.

The '68 B body 8 3/4 is wider drum to drum too, so you'll need rims with more backspacing. Not a great thing if you want to stay with 15" rims, but if you want to run 17" or 18" rims you'll have plenty of off the shelf options with the right backspace.
 
Yes, I meant drum to drum. So what does c-c stand for? Also, could you explain in a little more detail exactly what I would need to do to install the 8 and 3/4 axle? Thank you so much. Last, can it still be used with 15 inch rims, or will it just not work at all?
 
Center to center

Cut the spring perches off and weld new ones in the correct location

Yes, any wheel with the right bolt pattern that clears the brakes will work, the sticking point is the amount of room in your wheel wells.
 
The c-c measurement is center-to-center on the spring perches. No matter what you'll have to move the spring perches to match the A-body spring location, which puts the spring perches at 43". Unless you move the spring even further with a 1/2" spring offset.

You can use 15" rims still, I ran my Duster with 15x7", 4.25" backspace cop rims and 225/60/15's after I did the swap. But there wasn't any extra clearance, that's all I could run. The problem is you won't find a lot of positive offset 15" rims. And if you wanted to run wider tires you'd need a pretty significant positive offset. You can get 275's on a Dart Sport or Duster even with the stock spring locations. But to do that with a '68 B body rear you'd need like 6" to 6.5" of backspace.
 
This might help

Mopar_rear_axle_dimensions.jpg
 
Why not just swap the 2.76 open diff for a 3.23 suregrip in the 8.25 axle? The 8.25 is stronger than given credit and if you swap the 8 3/4 in, you'll need to have the driveshaft shortened and balanced.
 
halifaxhops said:
This might help

View attachment 1714967006
Click to expand...

It would help if it were right! Too bad most of those measurements are wrong!!!!!!!!

Worst chart ever. It always gets posted, it always gets flamed, and for some reason it keeps getting posted. It's wrong about most of the important measurements. A-body 8 3/4's? Wrong. B-body 8 3/4's? Wrong. Technically wrong about E body 8 3/4's, although it's only off by 1/64". But it's wildly inaccurate on the B body axles. Like listed one width for 62-70. There's 4 different width's for B body axles in that span, and none of them are 55". Here's an accurate list. I've personally confirmed the A, B, E, most of the C, and even one of the D100 measurements myself (although it wasn't originally my list). Also, using the flange to flange width doesn't tell the whole story, because on the SBP A-body 8 3/4 the drum to drum width doesn't change by the same amount because of the SBP brakes being a different offset.

For the OP, BBP 7.25 and 8.25" axles are 51.5" flange to flange. I measured the 7.25" axle myself, and confirmed with another member the 8.25's are the same.

8 3/4 Housing widths, flange to flange

A BODY
'66-'72= 52 5/8"

B BODY
'62-'63= 53 1/4" (And '64 Max Wedge)
'64 = 55 5/8" (Exc. Max Wedge)
'65-'67= 54 1/4"
'68-'70= 54 15/16"
'71-'74= 57 7/8"
'71-'73 wagon= 59 7/16"

C BODY
'65-'69= 56 3/4"
'70-'71= 57 7/8" (Chrysler & Fury)
'70-'74= 59 7/16" (and '69 wagon)

IMPERIAL
'65-'66= 57"
'67-'69= 57 3/8"
'70-'71= 54 3/4"
'72-'73= 59 5/8"

E BODY
'70-'74= 56 31/64"

A100
'65-'70= 56 3/4"

D100
'65-'71= 58 5/16"
'72-'74= 59 7/16"
 
Last edited:
Well, i have a '69 B-Body 8 3/4 in my '74 Dart Sport and all i had to do was cut off the spring perches and weld new ones on 1'' inboard on both sides. The brakes are new stock sized parts.
The car has 15X6 1/2'' stock rallye wheels off of a Cordoba on the back with 255 60 15'' tires.
When it was installed with the original stock saggy springs, it would slightly touch the sidewall to the quarter panel lip if you went fast over a bump.
I simply hammered the inner lip in (it is about an inch overlapped toward the tire) and there was lots of clearance.
Since then, i have installed Super Stock springs, so it's more of a non issue.
The inside offset of the rim is about 3 3/8'' and the tire is still almost 2'' from touching the spring, there is at least an inch to the inside of the quarter panel lip.
Getting a 275 60 15'' tire would be easy with the right wheel.
I would do it again in a heartbeat.........
 
74 dart sport said:
Does anyone know if a 8 and 3/4 rear axle from a 1968 B- body would fit in a 1974 dodge dart sport originally with a 8 and 1/4 rear axle (A- body)? The 8 and 3/4 axle is a 3.23 sure grip and the 8 and 1/4 axle is a 2.76 peg leg. Would I be able to just swap out the two? Are the measurements the same?
Thanks, Kameron
Click to expand...


Absolutely, I have one in my 74 Dart Sport. I moved the perches in on each side to get the 43' center to center measurement.

Keep in mind pinion angle when doing so. I scribed lines extending inward, removed the old perches and lined the new ones up with my scribed line and it worked out perfect. I run 15" 60 series tires on a 10" wide wheel with 5 1/2 inch backspace.
 
Ok, well my father and I have talked it over, and we have decided to just stick with the 8 and 1/4 and put some 3.23 or 3.55s in it. We also talked about the posi, and from his research, there isn't that large of a benefit from a posi. Thanks guys!
 
74 dart sport said:
Ok, well my father and I have talked it over, and we have decided to just stick with the 8 and 1/4 and put some 3.23 or 3.55s in it. We also talked about the posi, and from his research, there isn't that large of a benefit from a posi. Thanks guys!
Click to expand...

That depends on what you're going to do with the car. One of the first things I did with my duster was put posi in it. What are your plans for it? Ever plan to do a burnout?
 
Plans are : do a burn out once a year maybe (yes I know burnouts look lame with a posi)

And 350 is a good price. How much do you think labor would cost if we put it in at the same time we changed the gears? ( might as well put it in with the gears, since the axle housing will already be open). What are the pros and cons of a posi vs a peg leg?
 
Doing the change with the gears at the same time would be ideal. That way you'll only pay for labor once. Price for that is unknown. Find a drivetrain shop who does rear ends regularly. If you're 8.25 is the original, it's a 27 spline unit. The 29 slines didn't come out till 97
 
You can get sure grips out of jeeps and others with a dana 35, most have decent gears also. And the Cherokee disks can be simply modded for the 8 1/4.
Lots of info here.
The 8 1/4 thread
 
It's true you can find them in salvage yards, but for the price of a new one with bearings from a trusted source like Doctor Diff, it's hard to beat the price. And by upgrading his oem axle, no fitment issues, no shackles to relocate, no special offset rims to deal with.
 
I meant just the gears and the trak lok. I have done a bunch of them and usually 150 for both here.
 
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