.

 

What axles?

If your brakes are still stock (Dana 30/AMC 20) then a MC and booster for a cj with power brakes would do the job fine.

I could lock up 37's on pavement with my well maintained stock power brakes.

If you plan on 4 wheel discs in the near future stick with a Corvette MC. Bore size will depend on your caliper size.

For example with 1 ton 4 wheel discs I use a Vette MC with an 1-1/8 bore and no booster. This set up works very well.

 

There really is no legit listing for stock dual diaphragm booster for CJ7. Did they even come power?

I have some 'Vette master cylinder, but don't know what. What bore should I use with stock '86 D30/D44, and what should I use when I swap to Chevy calipers on all four corners (disc conversion using 70's Chevy calipers)?

There's a place that will sell me a MC, booster, and adjustable prop valve for $300-ish, but that's a awful lot if I knew what to go get myself.

 

I have been around a number of cj7's with stock power brakes. Run the stock stuff.

Edit: my 77 had them as well as my friends 83.

 

My 83 CJ7 had stock power disc/drum. If you want a dual diaphram, I understand you need to go late YJ.
Travis..

 

I've put a few dual diaphragm Corvette boosters on CJ's. You need a stock YJ firewall bracket, a 3/8" SAE fine thread grade 5 or higher coupler nut and you have to cut and thread the stock CJ pushrod to 3/8" SAE Fine to make the connection to the coupler nut. A vast improvement over the stock CJ single booster. You need to match the booster to the master. The one you want fit the third gen Corvettes, '68-'82. There's a split in the 70's, the later one uses Metric bolts at the fire wall bracket and the pushrod depth is different for the master cylinder. If you get them for the same year 'vette, either one will work the same. The holes in the stock YJ firewall bracket need to be opened up a bit to fit the Corvette's larger studs. (Early is 3/8" coarse, later are 10mm metric. YJ boosters are 8mm threads.)


A second way for better power brakes on a CJ:
The stock CJ brake booster uses a weird bracket with a bell crank that actually decreases the pedal leverage to the booster. Tri County Gear sells/used to sell an adjustable pushrod and tells you how to re-drill the firewall side of the bracket and the swinging link to bring back more leverage to the stock booster. The holes are relocated about 5/8" down on the bracket and link, making it more of a straight shot to the booster with a slight increase in pedal travel.

Jeep Brakes, Brake Install, Brake System, and Brake Upgarde - 4 Wheel & Off Road

Lastly, the YJ boosters with dual diaphrams are found only on '94 and '95 models. In '94 they were only on ABS equiped models. It's a bolt on if you use the YJ brake pedal arm and have the firewall bracket with the booster. I have a '94 booster and master on my CJ-8.

Hope this helps!

 

Thanks for the input. I figured out a solution that I'm pretty happy with. Not sure who else will beneift from it specifically, but may be able to adapt to their needs.

I had the brackets that I believe the PO installed, using a unknown booster and a Corvette style MC. I assume it was some setup from some website or the other. It did have the proper brackets, though, and relocated the brake line front-to-rear. That booster had a input shaft that was threaded well inside (3/8 fine thread), and a end that links to the bracket's swing arm.

I dug around on every website I could find and cross referenced who was using what MC on what booster with what setup, Jeeps, hotrods, everything. I eventually found that a '77-'82 Corvette was "perfect" so I ordered on up at the locals parts store and got it the next day. The input shaft was NOT threaded but 1/2" and could not be threaded. It was also 1.5" too long for my needs.

So now I had to either return the part and start over or adapt it.

I have a welder.

The bracket is now extended 1.5", my old end piece on the new booster, and everything installed.

I need to bleed it better and adjust rear brakes for best performance, but right now it will lock the 33's up. I have never had brakes this good in the 4 years I've owned it and I'm very happy with the results.

I hope this somehow helps the next poor guy with more time than money.

 

With the Corvette master conversion you do swap the CJ's original lines front to back, forgot to add that.

An original Corvette dual diaphragm booster has only a stub shaft coming out the back that is threaded 3/8" fine, maybe 4" long at most, no eye on it.

The YJ brackets ('87-'94 with a single diaphragm booster is the application) used to be available new at the dealer for under $10, but they have been long discontinued.

O'Reillys, has the Corvette booster/master assemblies for $122, exchange. Their countermen are usually pretty dumb, if you wait until the next day or for a shift change, return the old CJ booster and master for the core. :flipoff2: The core charge is only $20 anyways, if you don't have an old one to turn in.
BrakeBest 50-1200 - Power Brake Booster | O'Reilly Auto Parts

One more thing, if you do redrill the stock CJ pedal bracket, you really don't need the adjustable link. If you don't use it, the pedal ends up at about the height as the pedal is on a CJ with manual brakes. about 1" higher than it was stock with factory power brakes, about even with the clutch pedal if you have a manual trans. It just takes a day or two of driving it to get used to lifting your foot a little higher to hit the brake pedal.

 

So then the bracket from a early YJ instead of my modified one would have accounted for the additional 1.5" input shaft on the booster? I will keep my eyes open for one to swap down the road, if so. Thanks for the info.

Yeah, I got mine from O'reilleys. They do have a couple dummies that work there, but also a pretty intelligent manager and assistant manager who have told me that they really don't care what core I bring. They take good care of me there. I keep going back and keep going back. It's a good relationship.