'75 Dart Sport Front Drum to Disc Conversion

[shakotanboogie]

I've got a '75 Dart Sport I'm working on, a factory slant 6 car which has what I guess are pretty rare front drum brakes (with small bolt pattern I think?). I'm planning to swap over to Wilwoods so I'm curious what parts I'll need aside from the disc brake spindles. Are the control arms etc. the same for the '73+ front drum and disc cars? Thanks a lot, Mike

 

[Jimacuda]

Front drums arent rare on 73-76 A's. A lot of the slant sixes had them.
contol arms are the same, disc or drum 73-76. Lower ball joint is the same also.
Some disc conversion kits use the drum spindle. Check the manufacturers data to be sure.

 

[shakotanboogie]

Thanks much that helps a lot. Wilwood shows a drum spindle kit for the '72 and earlier cars but nothing for '73+ . Does that mean the '72 and '73+ drum spindles are different or is it just an oversight?

 

[4mulas]

Front drums arent rare on 73-76 A's. A lot of the slant sixes had them.
contol arms are the same, disc or drum 73-76. Lower ball joint is the same also.
Some disc conversion kits use the drum spindle. Check the manufacturers data to be sure.

Control arms are not the same. Disc brake upper control arms had a larger ball joint which also coincides with the spindle required for disc brakes. The lower arm is the same but does require the disc brake ball joint.

Also if you are sourcing the correct disc brake spindles I don't know why you want wilwood for the rest. Just get all oem parts.

 

[Jimacuda]

Control arms are not the same. Disc brake upper control arms had a larger ball joint which also coincides with the spindle required for disc brakes. The lower arm is the same but does require the disc brake ball joint.

Thats not correct.
Large ball joint uppers started in 73, all cars, drum or disc so they are the same. 73 to 76 used the same lower ball joint, no matter if drum or disc.

 

[Jimacuda]

Thanks much that helps a lot. Wilwood shows a drum spindle kit for the '72 and earlier cars but nothing for '73+ . Does that mean the '72 and '73+ drum spindles are different or is it just an oversight?

No, not an oversight. 73 up drum spindles are different than 72 back drum spindles.
I'd call Wilwood and ask them.

Also all drum brake A bodies had the small bolt pattern, right through the 1976 model year.

 

[4mulas]

Thats not correct.
Large ball joint uppers started in 73, all cars, drum or disc so they are the same. 73 to 76 used the same lower ball joint, no matter if drum or disc.

You're right. But they also used a left over glut of small ball joint upper a arms on 6 cyl drum brake cars.

 

[shakotanboogie]

No, not an oversight. 73 up drum spindles are different than 72 back drum spindles.
I'd call Wilwood and ask them.

Also all drum brake A bodies had the small bolt pattern, right through the 1976 model year.

Sounds good. Thanks a lot for the help. I'm thinking I'm just gonna go the disc brake spindle route as there's a lot more options available that way obviously. Sounds like the disc/drum spindles should be the only difference then?

 

[Jimacuda]

You're right. But they also used a left over glut of small ball joint upper a arms on 6 cyl drum brake cars.

A glut? hardly. Nothing beyond very early 73 would have been the 72 back parts.

 

[Jimacuda]

Sounds good. Thanks a lot for the help. I'm thinking I'm just gonna go the disc brake spindle route as there's a lot more options available that way obviously. Sounds like the disc/drum spindles should be the only difference then?

Should be, yes.
Any thought given to using "factory" disc brakes?
Lots of good options available...73-76 A body...76-88 F,M,J,R...late B...

 

[72bluNblu]

No, not an oversight. 73 up drum spindles are different than 72 back drum spindles.
I'd call Wilwood and ask them.

Also all drum brake A bodies had the small bolt pattern, right through the 1976 model year.

Actually, the drums went away by federal mandate in January '76. So, drums were still around at the start of the '76 model year, but only until January. Assuming the factory kept up with the federal mandate.

You're right. But they also used a left over glut of small ball joint upper a arms on 6 cyl drum brake cars.

That "glut" wouldn't likely have lasted past the first few months of production for the '73 model year. It wasn't uncommon for some parts to be "used up" despite a model year change, but as the owner of an August '71 built '72 Challenger I've done a decent amount of research into left over parts, since my challenger has a few. And usually, the model year leftovers never lasted more than a couple months. I'm no expert by any means and Ma Mopar has done some strange stuff, but if the small joint UCA's made December '72 I'd be really surprised.

Remember too that these cars are 40+ years old, and shade tree mechanics do weird stuff too, and that was true even a few decades ago. So, just because a later car has earlier UCAs doesn't necessarily mean it came from the factory that way.

 

[Jimacuda]

Actually, the drums went away by federal mandate in January '76. So, drums were still around at the start of the '76 model year, but only until January. Assuming the factory kept up with the federal mandate.

Thats correct, as of 1/1/76 front disc brakes were federally mandated.
Still, all 76 model year A body cars with drum brakes were small bolt pattern.

 

[shakotanboogie]

Should be, yes.
Any thought given to using "factory" disc brakes?
Lots of good options available...73-76 A body...76-88 F,M,J,R...late B...

Yeah either way the disc spindles give me options so that's nice to know. I'll do some more searching around to see exactly which route I go.

 

[72bluNblu]

And you don't need to find new UCAs since you already have the larger ball joints, so you just need the spindles, caliper brackets, calipers and rotors. Should be able to find that way cheaper than a wilwood kit.

 

[shakotanboogie]

Remember too that these cars are 40+ years old, and shade tree mechanics do weird stuff too, and that was true even a few decades ago. So, just because a later car has earlier UCAs doesn't necessarily mean it came from the factory that way.

That's a very good point. My car is a factory slant six '75 with drums up front, but the previous owner fitted an earlier style biscuit mount V8 K-member, and an 8 3/4 rear end. Wheels are the same front and back though.

 

[72bluNblu]

In that case, you'd better check to make sure you actually have large ball joint UCA's and the 73+ drum spindles before you buy anything.

 

[Jimacuda]

In that case, you'd better check to make sure you actually have large ball joint UCA's and the 73+ drum spindles before you buy anything.

What he said. That would have been good info to share from the beginning.

 

[shakotanboogie]

In that case, you'd better check to make sure you actually have large ball joint UCA's and the 73+ drum spindles before you buy anything.

Yeah I'll verify everything when I take the front end part. I guess there's a chance the previous owner moved over the whole front end to the earlier style and also installed a small bolt pattern rear end.

 

[4mulas]

Understood!

Here's a question, are the caliper mounts the same from diplomat and fifth ave line of cars as A body? Just would need to reverse them from side to side as the diplomat calipers are mounted on the rear? And splash shields?

This will help the OP in finding suitable donors.

 

[72bluNblu]

Understood!

Here's a question, are the caliper mounts the same from diplomat and fifth ave line of cars as A body? Just would need to reverse them from side to side as the diplomat calipers are mounted on the rear? And splash shields?

This will help the OP in finding suitable donors.

Yes, all that stuff is the same. If you can find an FMJ donor car it would have everything you need. You just need to swap the spindles side to side if you want the calipers mounted in the front. Although, mounting them in the back is better for sway bar clearance anyway, you just need longer brake hoses and careful routing.

 

[4mulas]

Yes, all that stuff is the same. If you can find an FMJ donor car it would have everything you need. You just need to swap the spindles side to side if you want the calipers mounted in the front. Although, mounting them in the back is better for sway bar clearance anyway, you just need longer brake hoses and careful routing.

For rear mount use 82 diplomat hoses. Actually anything that is 15" long. 69 camaro hoses work too