1973 Mustang straight axle swap

[48Ford]

I'm starting on my project again, it's a 73 mustang fastback. I have a 351w in it now but I found a 429 so I'm yanking the 351w back out. I'm gonna get weird with this one, since I already redid a 1972 coupe so I'm gonna have more fun with it. I used to build custom trailers and people would order them with lifts and all kinds of weird disires. I have a big storage unit full of all kinds hangers and shackles, and I'm pretty confident in my frame work and welding skills. I'm gonna turn it into a gasser, and I know "Gassers ended before 73" "Its not a real gasser" "I'm a poser" blah blah I don't care, it'll be different.  I'm going mild on raising the frontend up nothing crazy. I bought a 48 F1 straight axle, it has new leaf springs, bearings, new stock brake assembly and drums on it. I was curious if I could use the stock 48 brakes and drums with the 73 brake system? The 73 had all 4 drums on it. I own a orginal 1948 F1 since I  was 13 so I know the brakes on them can be a little dangerous especially with a 429 and 4 speed top loader, but the car has a long ways to go before its race ready so I'd like to drive it around during its build. So my question is can the 48 Brakes on the straight axle be used with the 73 mustang's brake system? Also any information on this build and what I'm going to run into is welcome besides criticizing it. Thanks!

 

[Don C]

The way I look at it is it's your car and you can do anything you want with it. It's not a super rare concourse trailer queen, either.

Yes, you can use the brakes on the '48, brake fluid pressure doesn't care what it is applied to. But, you are correct, the brakes will be even more marginal than they were especially with the added weight of the 429. I would strongly suggest an upgrade to both the front and rear brakes. You didn't say what size engine came in it originally, but because it has drums/drums I'm guessing the rear drums are the small ones.

Brake upgrades are available

https://www.speedwaymotors.com/1948-1956-Ford-Half-Ton-Deluxe-Disc-Brake-Kit-5-x-5-1-2-Inch,36492.html

 

[cwalker509]

Make it YOURS!

 

[48Ford]

The way I look at it is it's your car and you can do anything you want with it. It's not a super rare concourse trailer queen, either.

Yes, you can use the brakes on the '48, brake fluid pressure doesn't care what it is applied to. But, you are correct, the brakes will be even more marginal than they were especially with the added weight of the 429. I would strongly suggest an upgrade to both the front and rear brakes. You didn't say what size engine came in it originally, but because it has drums/drums I'm guessing the rear drums are the small ones.

Brake upgrades are available

https://www.speedwaymotors.com/1948-1956-Ford-Half-Ton-Deluxe-Disc-Brake-Kit-5-x-5-1-2-Inch,36492.html

It's a base model fastback that came with a 6 cylinder 250 and 3 speed manual trans. 8.8 rearend with small drums. I have a 69 f100 out in the pasture, I was thinking about yanking the 9" out of it, but I havent done much research on if that's gonna be more of a headache than it's worth. Definitely going to change the brakes on the car later on. I live out in the sticks of Kansas, so I'm not gonna kill anyone lol. I'd like to get the car how I want it, running and driving then start making it more safe and road worthy. Would the old mustang drums thats on the car work on the 48 axle? Would that be better approach? My 72 coupe has 4 drums and honestly I never had any complaints or "Oh sh*t" moments with them haha

 

[Don C]

No, I doubt if the Mustang drums can be made to work on the '48 front axle. Obstacle #1 is the bolt pattern, 4-1/2" on the Mustang, 5-1/2" on the '48. The hub and bearing sizes are likely different, so you won't be able to use the Mustang hubs on the '48 spindles.

The rear end in the pickup is 4" wider than the 57.25" axle in your Mustang. The only advantage is that the wheel bolt pattern is the same as the '48 wheels.

One of the easiest swaps is one from an Explorer. Here is more information about it

https://www.7173mustangs.com/thread-rear-end-suspension-and-wheels

The 429 weighs a lot more than the 6 cylinder did. More weight requires more braking force.

 

[48Ford]

No, I doubt if the Mustang drums can be made to work on the '48 front axle. Obstacle #1 is the bolt pattern, 4-1/2" on the Mustang, 5-1/2" on the '48. The hub and bearing sizes are likely different, so you won't be able to use the Mustang hubs on the '48 spindles.

The rear end in the pickup is 4" wider than the 57.25" axle in your Mustang. The only advantage is that the wheel bolt  pattern is the same as the '48 wheels.

One of the easiest swaps is one from an Explorer. Here is more information about it

https://www.7173mustangs.com/thread-rear-end-suspension-and-wheels

The 429 weighs a lot more than the 6 cylinder did. More weight requires more braking force.

I forgot about the explorer swap, my buddy did that to his Ranchero he made into a gasser. I'll definitely look into that. Believe they had limited slip as well!

Did the BB Mustangs have bigger drums? Because I was told the 6 cylinder drivetrain was the same as the SBF V8s besides the front springs. My v8 coupe has all the same drivetrain as the 73 even with the cute little drums in the back along with the 8.8 rearend. I have never seen a factory Big block 71-73 mustang in person, so I've always wonder what differences they had.

 

[48Ford]

I've got a local kid that has a straight axle from an F1 its already set up for disc brakes. I'm not very familiar with disc brakes though. What I see is what I get and he doesn't know what type of setup it is. Can you recognize what that is? Should I go ahead and pick this one up too? He wants 65 bucks for it

 

[Don C]

The drum diameters are the same, but cars with 351s and 429s had 0.25" wider shoes.

I can't help you on the other axle. It could be challenging trying to find calipers and rotors that fit. I would want to take a look at the spindles, see if they look as bad as the outside.

 

[clevelandcoupe]

For the disc brake set up, check out speedway motors or TCI, the brackets shown may be one of them.

Thanks, Jay

 

[Don C]

I have to correct myself, our years of Mustangs rear axle width is 61.25", the '69 F100 is the same width, 61.25". They (F150s) went 4" wider in 1973.