Ball joint trouble - Do I need new control arms?

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DemonSwede

DemonSwede

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Sorry if this issue has been addressed somewhere in the past, I tried to search for it but the main issue people seem to have with ball joints is the shaft and/or socket size! I'm in the process of doing a disc brake conversion on my -72 Demon. I bought the disc brake kit used (I believe it comes from like a -69 Dart) and it has the smaller shaft upper spindle hole (app. 0,55" diameter). I bought a set of new upper ball joints to fit this smaller spindle hole and they fit, but the issue is that the threaded part of the ball joint is too small to fit the hole in my upper control arm! The threads on my old ball joints that I used on my drum setup measure app. 1.8" diameter and the new smaller shaft ball joints measure only app. 1.6".

Now, is there a ball joint out there that has the larger diameter threaded body and the smaller diameter shaft or do I simply need to get new upper control arms with a smaller diameter hole?

The disc brake kit is fine otherwise and the lower control arm fits the lower ball joint and the steering rod fits as well so the only problem seem to be the upper control arm hole.

Thanks!
 
What do your brake calipers look like? Are they single piston calipers or 4 piston calipers? Pictures would eliminate any doubt.
 
The disc brakes are 4 caliper, see pic.

Yes, you are probably right in that I’ve got -73-6 control arms as this is not a genuine Demon but based on a late -72 straight six model. So will I be able to find ball joints that work for with these control arms?

EACC840D-F4F0-434A-B49F-36C5691027E0.jpeg
 
DemonSwede said:
And an old picture of the control arms if that helps

View attachment 1716042130
Click to expand...

It's hard to tell from a picture, but looking at the width of those front drums you might have the later 73+ brakes, which would also mean those are large ball joint UCA's. But it all looks pretty similar, the later brakes are only a little bit wider and the UCA's look exactly the same, except for the slightly larger ball joints.

There aren't any ball joints that have the larger outer diameter and the smaller tapered pin that I'm aware of. You'll either have to get a small ball joint set of UCA's (67-72) or ream the taper on the spindles to accommodate the larger ball joint.
 
Thanks, that’s what I suspected…

If I need to change, would you recommend going for tubular or find a used set of stock UCAs?
 
Depends on your plans for the car. The tubular UCA’s have additional built-in caster, which is really helpful if you’re running more modern radial tires. You can use Moog K7103 offset bushings with the stock UCA’s, but even with those you usually don’t get as much positive caster as with the tubular UCA’s. For a weekend cruiser with 15” wheels and skinnier tires it doesn’t matter much. For better handling and those running wider modern tires the offset bushings don’t really get you enough caster.

I think the QA1 UCA’s may be the only ones that offer a small upper ball joint? Could be wrong. I change all my stuff over to the 5x4.5” pattern and large ball joints.
 
Are those 4 1/2 inch bolt pattern rotors? They look to be. If not you will need wheels. I have seen rotors 4 1/2 bolt pattern but very rare on an early A-body. If they are 4 1/2 not you can use 68 mustang rotors with some modifications to the spindle for the bigger seal.

I have the a-arms if needed but there are plenty out there for sale from 67-72. They are the same with all brakes for all those years.

Keep the 4 piston brakes and make them work. Single piston are not as good. They have constant drag and wear. 4 piston calipers release completely run cool and free wheel easy . Nice score on the brakes. It is what I am going to use with 4 1/2 Bolt pattern mustang rotors.
 
Thanks all, appreciate it! Yes it is the 4 1/2 bolt pattern on the disc brakes, I have the smaller pattern on my current drums and 14’ wheels so I will need to get new wheels anyway to clear the brakes.
 
The cheapest and easiest solution is to get the small ball joint upper control arms.....used from 1960-1972. As mentioned, if you need more caster adjustment for some reason, the aftermarket parts would be a better choice.
 
cudamark said:
The cheapest and easiest solution is to get the small ball joint upper control arms.....used from 1960-1972. As mentioned, if you need more caster adjustment for some reason, the aftermarket parts would be a better choice.
Click to expand...

If you run any kind of radial tires, you need more caster than what the factory UCA's will give you with stock bushings. Offset bushings at the minimum, even for just a cruiser with stock-ish sized tires. Unless you like your car to handle like a shopping cart.

And honestly, the cheapest and easiest solution would probably be to ream the spindle for the larger taper. He's already got all the parts for that, just needs a reamer. $100 and a little bit of time, all his current parts fit. Probably be able to re-sell the reamer after too.

Speedway Tapered Ball Joint Reamer, 7 Degree

Might be entertaining later when someone tries to figure out why they have KH brakes and large ball joints, but that's already gonna be a thing with the KH brakes and the large bolt pattern.
 
The availability of the parts or tools in Sweden along with shipping costs might be the deciding factor. Stock upper control arms are usually easy and cheap to find....here in the U.S. anyway.
 
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