Those who have gone to 2005+ axles

ghohouston

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Guys, I am finally getting some progress made on swapping an 07 suspension into my 97. I have a few questions regarding braking. For the rabs valve, did anyone do anything to/ with it? Modify, got rid of it, etc? I'd like to hear anyones experiences. I swapped over to the F Superduty hydroboost and moved the brake pedal pin years ago. Problem is I don't remember if I replaced the master or not, as it's been a good 8 years or so since I did that. Which brings me to the next question, is the factory obs master adequate for the 4 corner discs? Is there any way I can tell which master I have ( is there a p/n stamped in them or anything)?
 

ghohouston

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Couple of pics with ye olde shitbox finally sitting on it's own weight in the ass end with the 07 rear end.
 

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Powerstroke Cowboy

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No answer for you, but have the same questions. I plan on doing the same axle setup in the future and would like to know as well. Following this one.
 

BrewTown

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I don't have definite answers, but traditionally swapping from drum to disc the master needs swapping, along with the proportioning valve. Drum vs. Disc takes a different amount of fluid to operate, and iirc drums need more pressure sustained in the lines to stay adjusted correctly. Something like 10 psi anti-drainback vs. 2 psi for disc.

I'm probably using incorrect terminology and figures, but I think there's something to look into.
 

Powerstroke Cowboy

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I don't have definite answers, but traditionally swapping from drum to disc the master needs swapping, along with the proportioning valve. Drum vs. Disc takes a different amount of fluid to operate, and iirc drums need more pressure sustained in the lines to stay adjusted correctly. Something like 10 psi anti-drainback vs. 2 psi for disc.

I'm probably using incorrect terminology and figures, but I think there's something to look into.
In your opinion what about the fact the OBS pickups have a combination of disc and drum brakes?
 

BrewTown

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In your opinion what about the fact the OBS pickups have a combination of disc and drum brakes?
They have different circuits front and rear, and a proportioning valve to allocate pressure. When I said traditionally, I should have been more specific and said from disc/drum to disc/disc.
On top of that, master cylinders can vary in size pretty dramatically, which changes the pressure ratio (foot to caliper) and volume of fluid moved (affects how far the pedal moves to apply appropriate pressure.) Although I don't know what bore the SD trucks or OBS trucks use, I have seen 3/4" bore to 1 1/4" I believe. I know pedal ratio can be changed as mentioned too, a throw vs. pressure trade-off.

All that said, they increased the size of the brakes too for that generation, with '05 F350 bigger than F250 as far as I know. Does that mean they 'tuned' the master along with that change? I don't know but I think there's a great possibility of it. None of this means the OBS one won't work at all, but it most likely won't be optimal.

Someone who has actually played with it and tested how it works would be a great resource. I have seen and played with an adjustable proportioning valve to stop the rears from locking before the fronts as a workaround. Never did have great brakes with that set-up. There may have been more going on there though as it's a '34 Plymouth street rod with a Dart 427 SBC, 700R4, Mustang 2 front suspension and 9'rear with Explorer discs. A whole mashup...
 

Tiha

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Factory master cylinder will work but it is not ideal.

I screwed around a bunch with proportioning valves on the factory master cylinder, did not make a bit of difference between stock and completely gutted and bored out.

Put the truck together and decide what you don't like about the brakes and go from there.

too much pedal travel? Then you need a bigger bore master cylinder.

pedal too stiff? Then you need a smaller bore master cylinder.

Then you just grab a master cylinder from a 4 wheel disc vehicle. I think I am currently using one from a 99 expedition, but the 99 superduty would work as well, just larger bore.
 

Strokersace

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When I did it, I left the rabs in place. Was also running the hydroboost prior with the obs master cylinder. When I did the 05+ axles, I swapped to the F-Superduty master with larger bore, and changed the proportioning valve. I cannot remember if the proportioning valve was from an 05+ Superduty or what though.

I did new pads and rotors at the same time. That was by far the best braking setup I’ve ever had!
 

KBMKVIII

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I just recently finished my swap.
No modifications to the existing brake system except new rotors/pads.
Just bent new lines and installed a new (same as oem) booster and master with new fluid.
Booster was leaking previously.
Brake feel is exactly how I like it.
Not mushy at all, steady pressure but not heavy whatsoever.
Stops 100times better than oem setup.
I’m not changing a thing
 

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