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I have a 1972 Jeep Wagoneer and need a new Brake Booster and Master Cylinder - but, it's not as simple as it should be:

I'm looking to replace the brake booster AND master and be done.

The axles/brakes are not original, they're out of an 86 Dodge w150 - drum/disc combo

No idea where the current booster and master came from.

Curious - what do I need to know to source a proper replacement for the Booster and Master? - eg: be able to mount to the firewall properly and pair with the stock brake pedal - and properly drive the drums and discs?

Thanks!!

Do you believe the booster and master cylinder came from a different application?

A '72 Wagonner came with 4-wheel drums, and a dual master cylinder, and 99% likely power brakes. I suspect the booster and master cylinder ar the originals. Look here https://www.rockauto.com/en/moreinfo.ph ... 15&jsn=408 - this is the original master cylinder. If you want, you can get a new one of these for about $40. Some of these cylinders have a residual pressure valve behind the brake line seat. You don't need it with front disk brakes, but it may or may not be present in your master cylinder.

If you have the original brake booster, RockAuto shows it as available rebuilt and is shown here https://www.rockauto.com/en/moreinfo.ph ... 12&jsn=412 - If this is what you have, you could just replace it with a rebuilt part.

I have never done this but I heard or read somewhere that the 74-80 FSJ booster and master cylinder are compatible in 68-73 models. What I read probably has more to do with putting the 74-79 Wagoneer axles (disk/drum) under an earlier drum brake Wagoneer. I could be totally wrong but would be looking at that option if it was me.

tgreese wrote:Do you believe the booster and master cylinder came from a different application?

I know for sure that the Booster isn't original, and I'm mostly sure the master isn't but can't confirm that. (previous owner did some really really random work on this thing)

But, I like the rock auto option, just grab both and go.

fulsizjeep wrote:I have never done this but I heard or read somewhere that the 74-80 FSJ booster and master cylinder are compatible in 68-73 models. What I read probably has more to do with putting the 74-79 Wagoneer axles (disk/drum) under an earlier drum brake Wagoneer. I could be totally wrong but would be looking at that option if it was me.

Do you know if there's any advantage to grabbing them off a newer FSJ?

turtlehead wrote:

fulsizjeep wrote:I have never done this but I heard or read somewhere that the 74-80 FSJ booster and master cylinder are compatible in 68-73 models. What I read probably has more to do with putting the 74-79 Wagoneer axles (disk/drum) under an earlier drum brake Wagoneer. I could be totally wrong but would be looking at that option if it was me.

Do you know if there's any advantage to grabbing them off a newer FSJ?

sometime ago such as BC, it was said that you could put the 79 and latter brake booster/MC combo on the earlier FSJ such as 74-78 which have the single diaphragm brake booster.

May be a pict of your set up will be helpful to our investigation unit!

turtlehead wrote:

fulsizjeep wrote:I have never done this but I heard or read somewhere that the 74-80 FSJ booster and master cylinder are compatible in 68-73 models. What I read probably has more to do with putting the 74-79 Wagoneer axles (disk/drum) under an earlier drum brake Wagoneer. I could be totally wrong but would be looking at that option if it was me.

Do you know if there's any advantage to grabbing them off a newer FSJ?

I would think the main advantage is the later parts have the same geometry as the earlier, so they will work with the existing firewall shape, dash and sled bracket. Plus you shouldn't have to figure out the push rod lengths. Should mostly bolt on.

I put newer ‘79 parts on my ‘73, had redrill 1 maybe 2 firewall holes IIRC. The ‘73 was oddball 1yr only setup.

‘83-‘91 uses a decent dual-diaphragm booster and gm style alum. master. If I was doing similar swap these days that’s what I’d use.

Thanks Tony! I knew this had been done to some extent before but my gray matter is less capable of storing the footnotes nowadays.

fulsizjeep wrote:Thanks Tony! I knew this had been done to some extent before but my gray matter is less capable of storing the footnotes nowadays.

I had my '73 build thread/dealio on here w/ pics and such, but when site crashed or whatever happened way back when it all went bye bye.
There was some good info in that thread on using later model brake parts on my '73.
My memory isn't great either, but overall it was pretty easy IIRC.