7.25 to 8.25 swap

[Brown8404]

Howdy gents,

I recently picked up a 1978 Dodge Aspen slant six car for parts for my 74 duster.
I removed everything including engine, transmission, the 8.25 rear end and other various parts.

My duster has the 7.25 rear end and it is also a slant 6 car. I heard swapping out the 7.25 is easy, but does anyone have any idea if the 8.25 out of the Aspen will just bolt up, and would it be worth it. any help on the swap would be great thanks

 

[Sedanman]

Does the aspen axle use the same style spring perches? If so then measure both axles center of perch to cewnter of perch and see what the difference is then measure width ouside of drum to outside of drum and see if it will fit.

 

[72bluNblu]

The F-body 8.25 will fit, but it's not a direct bolt in. The spring perches are 44.5" center to center instead of 43" for the A-body. It's wider as well. A BBP a-body 7.25 is 51.5" wide flange to flange, the F-body 8.25 is 54.3". It's very doable but it's not the same. (It's narrower than the 68-70 B-body 8 3/4 in my duster)

Also, any 7.25 to 8.25 swap will require the driveshaft to be shortened a little.

So, at the very least you'll have to weld on new perches and have the driveshaft shortened. And if your current wheel combo can't be moved out an inch and a half without rubbing, you'll need new wheels too.

Here's some axle specs, there are some 7.25 and F-body 8.25 specs in here as well. An accurate 8 3/4" rear axle width list

 

[Brown8404]

Awesome gents I appreciate the help

 

[Killer6]

Does the aspen axle use the same style spring perches? If so then measure both axles center of perch to cewnter of perch and see what the difference is then measure width ouside of drum to outside of drum and see if it will fit.

Not if it is equipped w/the "iso-clamp" system. The perch will have a large 1.25"(approx.) hole in it instead of the small center bolt head sized hole. No matter, you'll be cutting
them off to move 'em in anyway, so weld the correct ones on when you do.