M body rear in an A body?

[Jacksdad]

I originally tacked this on the end of another thread - sorry for the repetition. Okay - why, when I had no time (or money), were there a bunch of Aspen and Volares in the wrecking yards, but none since I started looking for an 8 1/4" for the Duster? What I did see though were a whole lot of Dippys and 5 Avenues with 8 1/4s. Lying on my back trying not to p**s off the black widows, I took some rough measurements (total width from flange to flange, and spring center to spring center) and compared them to the one and only Aspen, which had (of course) a 7 1/4, and a Valiant with the small rear end and found this;

M body 8 1/4 - 60 1/2" flange to flange, 44.5" spring to spring

F body 7 1/4 - 59" flange to flange, 44.5" spring to spring

A body 7 1/4 - 55 1/2" flange to flange, 43" spring to spring

I know the F body will fit the A body with the stock spring perch location if you don't mind spreading the springs a little, but it seems the M body rear has the same spring spacing, but a little more total width, which to be honest I don't mind as the Duster rear is too narrow anyway. My question is, has anybody used an M body rear in an A body without problems?

[5thAve]

You probably just saw a bunch of 7 1/4 axles in those cars. Pretty much the only ones that had 8 1/4 ones were police car and taxi Diplomats. Hardly any normal ones or 5th Avenues had them and usually the ones that do is because somebody changed it before.

[ehostler]

As your F-body and A-body measurements are off a bit, I would have to guess that you M-body measurements are also off.

I did not have any M-body measurements, so they were not presented in the axle dimensions diagram that is in the archives.

F-Body (ALL) 54.340" Flange-to-Flange 44.46" perch center-to-perch center
A-Body (1963-1972) 53.200" Flange-to-Flange 43.02" perch center-to-perch center
A-Body (1973-1976) 52.625" Flange-to-Flange 43.02" perch center-to-perch center

Spreading the springs for fit can be done, however it puts alot of lateral stress on the springs and mounts that they were not designed for. Eventually, something will bend or break.

[Leige]

Ever think of tossing in a 9" Ford rear end in your Duster? I have a 9" 489 posi Rear End out of a 70 mustang in my 71 Duster and from my understanding it matched up with no alterations.

[Jacksdad]

I told you they were rough measurements
Actually, problem solved. I finally managed to find a Duster with an 8 1/4 and gears I can live with (3.21) until I decide whether to got to an 8 3/4.
BTW - thanks Eddie. I printed up the A-518 stuff. Very informative. Appreciate it

[George G. Leverette]

The 8 1\4 rear end has the big bolt pattern, better rear brakes with parts easier to find, dosent cost as much and probably just as strong as tyhe 8 3\4 the only draw back is no drop out pig.

[dodger1]

And axles are (were?) available from Moser. To replace those axles with excess wear on the bearing surface (like mine )