Upper Control Arms in Disc Conversion

dozer556 said

True, but UCAs between disc and drum setups are the same, if you're talking the same ball joint size, right?

In other words, UCAs with LBJs work on disc OR drum LBJ spindles. UCAs with SBJs work the same way, on disc or drum SBJ spindles.

Duster_71 was asking if the UCAs were the same between the disc and drum LBJ setup, even though they had different part #s. I believe they are the same, even though you stated in an earlier post that you used 73-76 A body disc brake UCAs on your swap.

Not trying to make anything more confusing, but I guess this all boils down to whether or not there are different LBJ UCAs for disc and drum systems. I know the disc and drum spindles are different but I believe the UCAs are the same.

Click to expand...

According to the links I posted and what I have found there are two different upper control arms on A bodies. The disc brake upper control arms have a larger ball joint. The drum brake upper control arms have a smaller ball joint. This is probably because the disc brake can put a much higher load on the ball joint (better/faster braking). If you read all of the links I posted earlier you'll see which upper control arms have the large ball joint and which ones do not. You can't use the large disc brake rotors (like from a Charger) unless you convert to the large ball joint upper control arm and spindle because the disc brake B body spindle requires a larger ball joint in the upper control arm. You can rig it to work with a small ball joint but that would make no sense because of the higher loads. I know from the way my '69 Barracuda brakes....there is a world of difference in the stopping power now that I have switched to the big disc brake system.

The ball joints in disc brake and drum upper control arms are different!! When I ordered adjustable upper control arms for my Barracuda (after disc brake swap) there were different P/Ns for drum brake set-up versus disc brake set-up (different UBJs).

The lower ball joints are not an issue!!

Hope this helps.....

treblig