Disc brake identification

[cudafish65]

Hey all, I have a disc brake set currently on a b body but was told it was off an a body. I can't ID these numbers. Any help is appreciated

 

[72bluNblu]

It’s a slider set up, so it could be either one. Probably the biggest thing to be concerned about is the piston diameter, which you can measure. A-body single piston sliders used a piston that was 2.6” in diameter from ‘73 through ‘75, everything else used a 2.75” piston (including the ‘76 A’s). The larger piston gives you more braking force.

Some B-bodies used the pin style calipers depending on the year, so if you’re buying parts you’d want to make sure they’re for slider calipers. As long as they’re 2.75” pistons I wouldn’t worry about it too much, unless you’re trying to match up casting dates or something.

 

[hemi71x]

Well, A bodies, and B bodies, both used those slider type calipers, but with the differences in the rubber flex hose location on the caliper.
From what i can see in your picture, you most likely do have a 73-76 A body, disc brake set up.
Another difference is also in the spindles, between the two.
More pictures would be of help.
Those numbers on the calipers are pretty much meaningless to you and me, the common enthusiast.
They must have meant something at the foundry, manufacturing level, but nothing to do with identifying them, 40 + years later.
You gotta know what your looking at, in this case.

 

[72bluNblu]

Well, A bodies, and B bodies, both used those slider type calipers, but with the differences in the rubber flex hose location on the caliper.
From what i can see in your picture, you most likely do have a 73-76 A body, disc brake set up.
Another difference is also in the spindles, between the two.
More pictures would be of help.
Those numbers on the calipers are pretty much meaningless to you and me, the common enthusiast.
They must have meant something at the foundry, manufacturing level, but nothing to do with identifying them, 40 + years later.
You gotta know what your looking at, in this case.

Oh that's a good point, if it was a full conversion it might have the A-body spindles too.

You can look at the measurements for the A-body spindles here in Ehrenberg's article on disk swaps. Just ignore all his BS about "ball joint overangling" and not swapping spindles side to side. He didn't actually check any of the geometry, there's no doomsday scenario like he implies. I'd love to never link this article, but it is still one of the best resources for identifying the parts
DISC-O-TECH: Stop on a dime from Mopar Action and Rick Ehrenberg

If after looking at that article you have some fear of the horribly altered suspension geometry Ehrenberg claims will happen if you run different spindles, take a look at this article. Here they actually checked all the geometry and determined it wasn't a big deal at all. There are also some more pictures to help with identification of the spindles.
Swapping Disc-Brake Spindles - Mopar Muscle Magazine

All of the geometry is for running B (or more likely, FMJ) spindles on an A-body, not A-body spindles on a B body, but the changes are pretty minor in either direction in case you do have a set of A-body spindles.

 

[cudafish65]

Thanks for the info guys. I was thinking that they were late a body calipers but unsure of rest. Will do some more research in the coming days!