B-body axle in the A-body
Another alternative can be used to replace an existing 8-3/4" or the smaller 7-1/4" or 8-1/4" axles. An axle from a 66-70 B-body can be in- stalled in the A-body (note: a 62-64 axle can be used, but it does not contain the flanged axles of the later units). The later sport coupe style cars, Duster, Demon, Dart Sport, have the roomiest fenderwells. The 67-76 sedan and hardtop models have less. The 60-66 appear to be the tightest fit. The A-body has a spring perch spacing of 43.0", the 66-70 B-body is 44.0". To mount the B-body axle on the A-body springs, the perches need to be removed and new ones welded in place 1/2" inward from the original location on each side. The B-body track width is greater than the A-body. This may be a concern depending on the wheel/tire combination. The wider track enhances handling and aesthetics to some degree. This has been performed on the author's 73 Duster, now equipped with 15x6.5" rallye wheels and P255/60R-15 tires with 11x2.5" brakes. Originally setup with 15x7" rallye wheels and P275/60R-15 tires will rolled fender lips. The larger tires exhibited scrubbing when loaded on dips/bumps. If replacing a 7-1/4" or 8-1/4" axle, the driveshaft must be changed as the axle centerline to yoke centerline is greater for the 8-3/4" (12.35" vs. 10.09" for 7-1/4" and 11.69" for 8-1/4"). If changing a 7-1/4" axle the shock plates and u-bolts/nuts must be changed to the larger units from an 8-3/4" car.
Granada rear-end in a Mopar A-body?
The Ford axle is an 8" unit. So yes, its stronger than a 7.25" (anything is). The center drops out like the Chrysler 8 3/4 and Ford 9". If so, its a good thing. The only drawback to an 8" is that gears and posi units are harder to find than an 8-3/4.
The 8" Ford is a drop in replacement. Everything lines up, you need to use the mopar barking brake cables and a Ford/Mopar adapter U-joint.
The overall width of the Granadas 8" Ford axle is 57", the overall width of an A-body axle is 56 1/4". The spring perches are the same at 43".
The 8" Ford axle from the Granada is 3/4" wider then the standard A-body axle. The spring perches are in the same location. They use 3" U bolts, so 8.25", 8.75", 9.25" shock plates are needed. The 7.25" driveshaft should bolt on with an combination U joint. I would suspect that they weight about the same as the 8.25". Street Rodder has an article on the available drum brake packages for this axle in the current issue (two Ford, one Currie). There are several disk brake setup available, one from CE, one from Currie and there are most likely others.
Some Granadas had 9" units! , check the bottom bolt. if you can fit a box end wrench on it 8", if only an open end fits, 9" !
The Ford 9" and/or 8.75" axles will be found behind 351 powered Granadas/Monarchs. Everything else, used the 8" axle. Avoid the 8.75" axle, it is not supported by the aftermarket nor Ford. This axle can be identified by the bolt on rear cover. It looks vaguely like the 8.8" axle.
Some 8" Ford axles are a drop in replacement in an A-body as far as width of spring perches. Of course the 8" is not as strong as the 9" but it's good enough for most slant sixes and is not too heavy. It's a cheap non-permanent modifiation which might look like the 8 3/4 at first glance. I like the looks of the banjo type housing. The 8" Ford is the removeable carrier type like the Mopar 8 3/4. These go for $60 at the local pick-n-pull. I rarely see an A-body 8 3/4 in a salvage yard for a price that I can afford, plus those have the 4" bolt pattern which require new axle shafts for better wheel choices.
A buddy of mine with a '66 Mustang weighed his 8" 2.90 open center section at 55 lbs.
My 8.75" 2.94 open is 69 lbs. 3.91 SG is 75 lbs. 8.75" A-body housing (bare) is 40 lbs, and the small-bolt axles w/brngs are 33 lbs. 10X1.75" brakes are another 20-25 lbs - total around 175.
I bet the 8" with regular drums is around 25-30 lbs lighter than an A-body 8.75"
The Ranger rear end is a 7.5", also found in Bronco II , many are traction-locks, most had a 3.45, 3.73, or 4.10 ratio and parts are cheap because the same carrier came in mustangs etc. with V6s. These might be a good option.
The width is about 1/2" narrower than an A-body rearend and it's got the 4 1/2" bolt pattern. I'll have to move the spring pearch's to the bottom of the axle housing. But this thing looks big and strong when you put it up next to a 7 1/4" mopar.
Pinto wagons have 8" axles with 3.50 gears. The carrier drops out like an 8 3/4.