5 Lug Swap Power Booster Question

1 bad pony

New Member
Jan 7, 2013
Los Angeles
So I'm in the middle of a 5 lug swap using all 95 gt suspension and brakes. I was wondering if any of you have already done this and which booster to use... I have the 95 booster but the bolt pattern is different than the fox body one. So could I use the fox booster with the 95 master cylinder??? And then I noticed that the driver side front brake bypasses the proportioning valve and goes straight to the caliper??? What do I do about that??? Hahaha any advice is very appreciated!!
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i'm familiar with penetration
Mod Dude
Feb 18, 2001
This swap is pretty similar to a swap done on a 5.0, so you can ask there as well

Basically if you are using 95GT front and rear brakes then you need the 94-95 GT/V6 MC and booster

Yes, the bolt pattern is a little different. 3 holes line up, 1 does not. You can slot/redrill for this one. OR, you can purchase a 1993 Cobra master cylinder which is virtually the same (some would even same the same) but featured the correct Fox-specific bolt pattern and thread pitch (SN95 is metric, Fox is SAE).

As for the brake line plumbing...yes. It's unique. You can't use your original MC though., you'll need the SN95 MC. If you are using 95 GT front and rear brakes, the 94-95 GT/V6MC is your choice. You'll need a 3-2 port conversion to install it.


I’m not much help unless you’re looking for ****!
Mod Dude
Nov 29, 1999
Morgantown, WV...where couches meet their doom
I never realized the booster made that much of a difference. On my old Turbo Coupe, when I converted it to vacuum-assisted brakes (instead of the factory electronic ABS junk that broke), I used an SVO master cylinder and a 5.0 Mustang booster (with 73mm front calipers). The standard Thunderbird booster was ginormous whereas the Mustang booster was a good bit smaller in diameter, and I needed that smaller diameter to fit around all the wiring harnesses the Turbo Coupe had in that area. I don't really understand the difference since they all had the same brakes. Anyway, it all worked pretty well for me.


i'm familiar with penetration
Mod Dude
Feb 18, 2001
I usually recommend to try it first, but don't be surprised if you find you need to stand on the pedal to get the car to stop. Also, you can usually "cheat" a bit if you undersize the MC slightly to gain more mechanical assist vs vacuum assist.

When i did my Cobra front and rear brakes, i left the fox booster in. Stopping the car felt like doing quad excercises. I could stop the car fast, but it took a lot of pedal effort. I swapped to an SN95 booster and it greatly reduced the amount of effort needed.

I find brake feel to be reliative to the individual user. I drove an explorer the other day with 150K miles. Brake fluid was BLACK! Obviously never bled. Pedal was spongy as hell. I recommended a brake fluid flush to my friend who shot it down saying the pedal "felt great and they don't like sensitive brakes" . So to each their own. I garantee you there are guys out there than prefer the firmer pedals associated with leaving the fox boosters.
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