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A body rear end in a B body

Convert66

Convert66

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Getting settled in a new place and starting a new project. Moved to south west Georgia a couple years now, still getting used to the place. And now working on a 69 satellite. It has a bad 8 1/4 rear in it and I have a good 8 1/4 limited slip from a 74 duster . B body rear is 60 inches wide and the A body is 57 inches wide. Has anyone ever done this swap. Looking for insight.
 
Never did the swap but it looks like you would have to change the wheel offset a little. But would this cause you to have to change the rear leaf location? Not sure I would assume you would have to check from the back of the wheel to the leaf spring just to make sure you have clearance. I'm not an expert but I do play one on TV maybe someone with more knowledge will drop in and help you out.
 
What's wrong with the satellite diff. If the ring gear extra is bad could you just swap center sections.
 
He said its an 8 1/4 it has a back plate and doesn't come out the front like a 8.75
 
I should drink my coffee before reading post. Sorry
 
Spring perches won’t be in the same spot

B body 8.75 diffs are usually readily available and inexpensive. Sell the A body sure grip and buy a 8.75. ?
 
Does the A body rear still have the small bolt axles? If not, that's an extra cost or work to change it. A buddy of mine did that....re-drilled the axles but that's not exactly an easy chore either. I'm with 4mulas comment above. The A body rear ends bring a premium price and if you look around a bit, the B rears are reasonable still....a 66/67 also is a good fit.
 
Cranky said:
Does the A body rear still have the small bolt axles? If not, that's an extra cost or work to change it. A buddy of mine did that....re-drilled the axles but that's not exactly an easy chore either. I'm with 4mulas comment above. The A body rear ends bring a premium price and if you look around a bit, the B rears are reasonable still....a 66/67 also is a good fit.
Click to expand...

He has an A body 8.25” which is ‘73 and up. It has Large bolt axles and not as valuable as an A body 8.75” as they seem less desirable by most. They can handle descent HP but if you start going high horse build the 8.75” is stronger.
The 8 1/4” is quite capable though and as a suregrip does hold some value. I’ll let others determine that. My off the cuff guess is maybe $500-700 complete maybe 800 even, whereas the small bolt 8.75: diff drum to drum to drum with a sure grip is more like $1500
 
What gears are in the A? They used some mid 2 series gears for economy in the 70s.
you can Move the spring perches and run it or depending what broke,switch the gears and carrier, or maybe just the carrier?
Imo..An inch in on each side is not noticable, maybe even desirable. I know guys that have done the b in a A body, rim with the right back spacing and it will be same.
 
If it was me swap the gear set. Aslong as the SG carrier is for the lower gear ratio like 321s in the Duster you should be good. Lots of info on this @ FABO.
 
I put a A body rear under a 72 B Body. First things first. Measure axle flange to axle flange on both the A&B housings.
Next measure the spring pad centerline of both axles. If you are within 1-2'' difference you can get offset front and rear spring hangers.
Splitting the difference per side you may be able to hang it quite easy.
Doing a search here, there are many posts showing charts of rears and the different widths per different years.
That should get you in the ball park.
Unless you throw some big HP at it and or it's a automatic I wouldn't be afraid to use a 8 1/4'' rear. A 74 dart Sport 360 4 speed came with a 8 1/4''. Basically all HP models had 8 1/4'' from 74-to 80ish ( in different body styles ) as the 8 3/4'' was phased out.
 
Last edited:
I narrowed a C body housing to approximately the A body width for my Charger. The spring perches were set to the 44" number the 70 B body uses. This was done to reduce tire rub. I didn't like how the tires were tucked in so I switched back to a stock 68-70 B body housing.
Yeah, it does fit but the tires will sit in further than you may like/
I agree though that changing the gears and differential would be the better way to go, though it will cost more. Moving spring perches can be done with a grinder and welder in a little over an hour for little cost. Setting up gears usually requires the help of a professional.
 
bearman said:
What's wrong with the satellite diff. If the ring gear extra is bad could you just swap center sections.
Click to expand...
Just wore out, the A body rear is all done and it’s a 3.21 limited slip. Also it’s narrower so I gain 1 1/2 inches on each side, which should make the rear tires to stop rubbing.
 
Kern Dog said:
I narrowed a C body housing to approximately the A body width for my Charger. The spring perches were set to the 44" number the 70 B body uses. This was done to reduce tire rub. I didn't like how the tires were tucked in so I switched back to a stock 68-70 B body housing.
Yeah, it does fit but the tires will sit in further than you may like/
I agree though that changing the gears and differential would be the better way to go, though it will cost more. Moving spring perches can be done with a grinder and welder in a little over an hour for little cost. Setting up gears usually requires the help of a professional.
Click to expand...
The A body perches are 43 inch , I remember years ago Mancinis had off set shackles for this .apparently they don’t make them anymore. Moving the perches a half inch on each side is no big deal .I was hoping someone had done it before and had some insight.
 
Darter6 said:
I put a A body rear under a 72 B Body. First things first. Measure axle flange to axle flange on both the A&B housings.
Next measure the spring pad centerline of both axles. If you are within 1-2'' difference you can get offset front and rear spring hangers.
Splitting the difference per side you may be able to hang it quite easy.
Doing a search here, there are many posts showing charts of rears and the different widths per different years.
That should get you in the ball park.
Unless you throw some big HP at it and or it's a automatic I wouldn't be afraid to use a 8 1/4'' rear. A 74 dart Sport 360 4 speed came with a 8 1/4''. Basically all HP models had 8 1/4'' from 74-to 80ish ( in different body styles ) as the 8 3/4'' was phased out.
Click to expand...
Your right ,there is only a half inch on each side to make up for. B body perches are 44 and A body’s are 43. Mancini used to have the offset shackles but stopped making them.
 
I've modified several B and C body housings to fit A body cars but only once have I done it the other way.
Tire clearance is often a matter of choosing the proper offset/back spacing of the wheel. The leaf springs are in line with the edge of the inner wheel tub so you aren't gaining anything by going to a narrower axle unless you're rubbing at the outside. The B body cars had this oddly shaped outer wheel tub where the arch does not match the quarter panel. In a perfect world, they would have ran the outer tub in parallel with the quarter skin to maximize the tire clearance. AMD has started making wheel tubs in this fashion. The pictures below show the weird design the factory came up with along with a custom solution.

Jigsaw RWT 1A.jpg
JIgsaw RWT 2.jpg
W T 1.jpg
WW 5.jpg


I still suggest the gear swap. The stock axle in your car is still fairly narrow.
 
Kern Dog said:
I've modified several B and C body housings to fit A body cars but only once have I done it the other way.
Tire clearance is often a matter of choosing the proper offset/back spacing of the wheel. The leaf springs are in line with the edge of the inner wheel tub so you aren't gaining anything by going to a narrower axle unless you're rubbing at the outside. The B body cars had this oddly shaped outer wheel tub where the arch does not match the quarter panel. In a perfect world, they would have ran the outer tub in parallel with the quarter skin to maximize the tire clearance. AMD has started making wheel tubs in this fashion. The pictures below show the weird design the factory came up with along with a custom solution.

View attachment 1163479 View attachment 1163480 View attachment 1163482 View attachment 1163483

I still suggest the gear swap. The stock axle in your car is still fairly narrow.
Click to expand...
I like the wheels that are on the car but if the air shocks bleed down the tires rub. I’m hoping that with the A body rear I’ll be good with regular shocks. Moving spring perches is no big deal , it’s only a half inch on each side.
 
Kern Dog said:
I've modified several B and C body housings to fit A body cars but only once have I done it the other way.
Tire clearance is often a matter of choosing the proper offset/back spacing of the wheel. The leaf springs are in line with the edge of the inner wheel tub so you aren't gaining anything by going to a narrower axle unless you're rubbing at the outside. The B body cars had this oddly shaped outer wheel tub where the arch does not match the quarter panel. In a perfect world, they would have ran the outer tub in parallel with the quarter skin to maximize the tire clearance. AMD has started making wheel tubs in this fashion. The pictures below show the weird design the factory came up with along with a custom solution.

View attachment 1163479 View attachment 1163480 View attachment 1163482 View attachment 1163483

I still suggest the gear swap. The stock axle in your car is still fairly narrow.
Click to expand...
Makes you wonder what the factory was thinking.
 
Convert66 said:
Makes you wonder what the factory was thinking.
Click to expand...
I am pretty sure that they didn't think. Body overhang was common on many cars. Tires sucked and tucked in were the way that they looked. The 8% of the buyers that cared enough to mount wide tires just did as you did, install air shocks or longer shackles to lift the rear. As time went on and with the "Pro-Touring" theme gaining in popularity, the style of a jacked up rear end sort of faded. I like running tires that fill the wheelwell because it looks like a NASCAR type of setup.
Nascar:
Charger NC 1.jpg


My car:
Bad mu fu.jpg


I have the dreaded wheel tub problem in this car and plan to address it.
I did a practice run on my other car.
Same model, 1970 Charger. I simply made cuts that sort of resemble football stitching:

Jigsaw RWT 5.jpg


Jigsaw RWT 7.jpg


Jigsaw RWT 18.jpg


Jigsaw RWT 21.jpg

Jigsaw UC B.jpg

Tire clearance greatly improved for almost NO cost aside from welding supplies.
Do you have a welder?
 
Kern Dog said:
I am pretty sure that they didn't think. Body overhang was common on many cars. Tires sucked and tucked in were the way that they looked. The 8% of the buyers that cared enough to mount wide tires just did as you did, install air shocks or longer shackles to lift the rear. As time went on and with the "Pro-Touring" theme gaining in popularity, the style of a jacked up rear end sort of faded. I like running tires that fill the wheelwell because it looks like a NASCAR type of setup.
Nascar:
View attachment 1163494

My car:
View attachment 1163495

I have the dreaded wheel tub problem in this car and plan to address it.
I did a practice run on my other car.
Same model, 1970 Charger. I simply made cuts that sort of resemble football stitching:

View attachment 1163496

View attachment 1163497

View attachment 1163498

View attachment 1163499
View attachment 1163500
Tire clearance greatly improved for almost NO cost aside from welding supplies.
Do you have a welder?
Click to expand...
Yep, love the metal and fab work. Hate the finish work.
 
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