Rear end swap

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DartGT360

DartGT360

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Would anyone be able to offer an opinion or share any experience. I am trying to find out if an 1980 Dodge Aspen rear end will work on a 1969 Dart. My Dart has the small bolt pattern and we want to swap that out.

Alternatively would it be possible to weld over and drill new stud holes on 4 1/2 centers on existing hubs and drums?


Thanks for your time.
 
Okay lacking a little about what you have but here goes.
What rear end do you currently have in your car?
If you have the 7.25 rear, they also made a 7.25 big bolt pattern axle as well
If you have the 8.75 (unless you're going to a Dana, why do you want swap it?) just call dr. Diff and order a set of BBP axle for it.

If you have the 7.25 rear and are looking for an upgrade, just get the 8.25 rear out of a 73+ A body. These will be BBP already but do know they come in two different forms depend on the gears inside, the housing is different. Try to get one the has at least 2.91(or num higher) this way you can go to the local junkyard find a 96 or older jeep grand Cherokee and pull the better gear and limited slip unit and install it into the A body 8.25 rear. If the jeep also has rear disc brakes take those as well because it's bolt on deal for the 8.25 rear!
 
The '80 Aspen should have an 8.25" rear axle, so if you have a 7.25" it would be a nice upgrade. It will work, but you'll need to relocate the spring perches. The axle is also about 2" wider than the A-body rear. Not a big deal, but you'll need about an extra 1" of backspace compared to a car with an A-body rear axle. So, typically in the back a 15x8 with 4.5"-4.75" of backspacing works, your car would need a 15x8 with ~5.5" to 5.75" of backspace or so. Those are just rough numbers though, I would definitely check that before I bought new wheels.

As far as welding hubs and re-drilling, are you talking about the front?

If you are, I wouldn't bother. If you have access to an '80 Aspen, just pull the spindles and brakes off of it and convert to BBP disks. The Aspen will have everything you need except for the large ball joint upper control arms to go with the spindles. And you can always just buy ball joint sleeves from Dr. Diff if you don't want to swap out your UCA's. http://www.doctordiff.com/a-body-upper-ball-joint-tapered-adapter.html
 
As for your drums, don't bother welding the old holes. Just drill the new ones for the 4.5" bolt pattern.

Oops, '72 beat me to it.
 
Thank you for the information. I am told my rear end is an 8 3/4 with 3;55 gears. SBP We have replaced the 360 cid with a stock 318 cid and want to go to 15 inch rims all around. Front already is converted to BBP disc brakes. New axles look like the way to go.
 
DartGT360 said:
Thank you for the information. I am told my rear end is an 8 3/4 with 3;55 gears. SBP We have replaced the 360 cid with a stock 318 cid and want to go to 15 inch rims all around. Front already is converted to BBP disc brakes. New axles look like the way to go.
Click to expand...

If you already have an 8 3/4 I would definitely not swap it for an 8.25!

Just buy new axles and brakes. On that note, you can use the brakes (backing plates, drums etc) off of that Aspen. A lot cheaper than buying a new set up.
 
As I recall the A-body specific 8.75 has different spacing from axle flange to backing plate than other mopar rears. There are several posts that address what parts should fit though.
 
mguner said:
As I recall the A-body specific 8.75 has different spacing from axle flange to backing plate than other mopar rears. There are several posts that address what parts should fit though.
Click to expand...

Only the SBP axles/brakes have a different flange offset.

BBP brakes and axles have the same flange offset for all applications, so you can use BBP backing plates from any 7.25/8.25/8.75 or Dana 60 with BBP axles.

What you can't do is redrill the SBP axles to BBP and use stock BBP brakes, or use stock BBP axles with re-drilled SBP brakes. If you re-drill the SBP axles you have to use SBP brakes and redrill the drums, and if you use BBP axles you need to use BBP brakes. The only exception to that is if you buy aftermarket BBP axles with the SBP flange offset, which you can do. Why you would want to spend the money on aftermarket BBP axles and then hamstring yourself by re-using your re-drilled SBP brakes I don't know, but you can get aftermarket BBP axles with the SBP flange offset.
 
you will need to weld plates over the spring seats and drill new holes for the spring center pins the f bodys use rubber insulators around the springs mounts, and the spring seats are wider as is the drum to drum measurement, so might need to cut off the spring mount and move them closer.
 
teringer said:
you will need to weld plates over the spring seats and drill new holes for the spring center pins the f bodys use rubber insulators around the springs mounts, and the spring seats are wider as is the drum to drum measurement, so might need to cut off the spring mount and move them closer.
Click to expand...

The spring perches are 44.5" c-c on the F-body's, A-body's are at 43"c-c. To use the F-body axle you'd have to cut the perches off and weld new perches on anyway, so there's no point messing with the stock F-body perches. Just get the correct perches and weld them on.

Sounds like the OP has an 8 3/4" anyway, so there's no reason to swap to the 8.25.
 
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