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Discussion Starter · #1 ·
Hello guys,

So after much deliberation I've decided I'm going to replace my 12 bolt with a 9 inch Ford. The planned changes are:

1. Narrow a current 9" housing I have to get to 6" narrower than what I have now with my 12 bolt, wms to wms. Needs to pull each wheel in 3".

2. Changing gears to 3.50's +/- with a Detroit locker.

3. Going with 31 spline Moser axles.

4. Want to convert to disc brakes that I can use my 5x5 bolt pattern GM wheels with.

Sooooo these are my questions.

I am going to.use my leaf spring set up with drop shackles. I know I will need to add pads and shock mounts. What measurements do I meed to be aware of (considerimg the pinion offset on the 9") other than the wheel mounting surface distance and where the pads and shock mounts go? Difference in thickness between GM drums and disc rotors? Pinion angle with drop shackles?

Also, does anybody know of the most efficient way to get to disc brakes that will allow me to use my 5x5 wheels with them? I do not want to use wheels adapters. I'm narrowing the rear so should I use different ends when welding it back up to make the brake conversion cheaper / not as much work?

Any other measurenents or engineering issues to consider?

Thanks in advance.
 

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What are you trying to accomplish with this swap? It’s going to be a lot of work, so I’m trying to understand what benefit it provides.

The GM axles in squarebody trucks are not perfect, but they are durable overall, and there are many parts available if something breaks.
 

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Discussion Starter · #3 ·
What are you trying to accomplish with this swap? It’s going to be a lot of work, so I’m trying to understand what benefit it provides.

The GM axles in squarebody trucks are not perfect, but they are durable overall, and there are many parts available if something breaks.

Just want something that is stronger than a 12 bolt to handle upcoming power upgrades, that will also eliminate c clips, and I have several 9" rear ends laying around. I'm not worried about the work. Just want to get it done. And part of me just wants to do it.
 

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check that the pinion comes out where you want it in relation to the track width.
get tapered axle bearings unless a drag only deal.
many many kits for rear disc brakes, they will move the wheel out 1/4 inch or so, put that in your calcs if you are that tight on clearance.
 

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Discussion Starter · #5 ·
check that the pinion comes out where you want it in relation to the track width.
get tapered axle bearings unless a drag only deal.
many many kits for rear disc brakes, they will move the wheel out 1/4 inch or so, put that in your calcs if you are that tight on clearance.
Thanks for the insight sir. I appreciate it.
 

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As far as narrowing goes there are several diffrent factory 9" widths. You may find a factory housing that does not need to be narrowed to match your intended width.



Keep the drums.
Drill them for the 31 spline 5x5 bolt pattern.

I just saved you tons of cash and headaches.

Unless your racing drum brakes will work just fine. More pad area means more friction at cold temps. Street ride they are better in most cases. Weight wise they are slightly heavier. But only slightly in most cases like less then 10lbs. That is a diffrence. But worth the few hundred and headaches and lessened cold street breaking performance it may not be justified.
 
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