5.3L Chevy Motor Swap – Jeep CJ Brake Upgrades

Remembering back when I was on the trail with the Jeep previously… this thing was HARD to stop going down hill in 4 wheel low range… so I started doing some research on ways that I could address this issue.. especially now that I am going to have a big powerful v8 sitting in the engine compartment. I don’t want to have to bring a new pair of shorts every time I go wheelin. Plus, it would be nice to be able to have enough braking power to lock up the wheels when I’m on the highway… because before, while I had no troubles stopping the jeep on the road, it just didn’t have the power in the system to stop as quick as I wanted.   Time to upgrade!

I was reading in very brief research that a booster/master cylinder unit from a Jeep Wrangler would be a great upgrade..so I went to the salvage yard and picked one up for cheap… well, come to find out, it won’t really give much if any performance boost over the stock CJ booster/master cylinder unit… so DANG, time to hit the drawing board again…and now I have another fairly useless part that I have to sell…. joy unspeakable.

So, after literally hours of REAL research, it led me to this decision point… either buy a hydro boost system (to expensive),  buy a VanCo power brake system (again pretty expensive), or do some major modifications and put something like a E350 van booster unit with a corvette master cylinder in (too much work), OR find a dual diaphram booster unit from a 1995 Jeep Wrangler Sahara or RioGrande model (but it has to be from a 6-cylinder Jeep, the 4-cylinder models do not have this dual diaphram booster unit).   THATS THE TICKET!  So the search was on for the 1995 Wrangler Sahara booster/master cylinder unit.   After calling dozens of Jeep salvage yards across the country (I used the website  car-part.com to find listings of yards that supposedly had this unit or a unit from a 1995 Wrangler 6-cyl) I found a couple of places in other states that had them…but they wanted like $200 bucks minimum and wouldn’t confirm for me with a picture or anything that this was the correct booster/master cylinder combo.   I know after doing the research that these units have a plastic master cylinder reservoir, and the booster section is about 9 inches deep… at least 2 inches deeper than the standard booster units…with that booster it should provide about 1500-1600 PSI of stopping power, versus the 1000-1100 PSI that the stock single diaphram units provide, and I read in several boards that guys were able to easily lock up 37″ tires on the highway with this dual diaphram unit… that was enough to make me wanna buy one right there!

almost coughed up the 200 bucks for a unit from some jeep salvage yard that told me they had one (apparently the JEEP salvage yards know how desirable these particular units are)… until I ran across a salvage yard (not a Jeep specific yard) in Florida that emailed me back telling me they had one.  I called them immediately and asked the gal who answered the phone about it, and she did a quick lookup on her computer and verified that it met all of my questions…so I asked her to take a picture of it and email that to me, and she was kind enough to do that… when I got the picture back I was excited and told them to pack it up and ship it out immediately, especially after she told me they only wanted $75.00 for it!   CHA-CHING!!!!!!   So I got it, and got to work!

Here is a picture of 3 booster/master cylinder combinations that Jeep has offered in their power brake systems from the 80’s (on right) through the year 1995 (on left):


The Dual Diaphram YJ booster unit is on the left, the standard 1995 YJ single diaphram booster is in the middle, and the stock CJ single diaphram booster is on the right.

If you undertake this project…. BEWARE that it is NOT a direct bolt in type of thing… the bolt holes for the firewall will line up, but there are modifications you will need to make to the shaft length as well as putting on new flare nuts at the end of your hard lines, because this dual diaphram YJ unit has metric connectors on it, not SAE.  Also, if you didn’t get the rear bracketry, you will either have to fabricate something up, OR do what I did and take the bracketry from a regular single diaphram booster (the one in the middle) and use it …but when you do that you will have to bore out the bolt mounting holes to allow the thing to slip over the bolts that come out of the dual diaphram booster unit rear. In this next picture I am trying to show you the difference in the lenghts from the rear bracketry mounting surfaces to the end of the shafts so you can see how this needs to be addressed:


You can see if you look closely at the left side, there is about 1/4 inch difference in length on the 1995 dual diaphram booster unit shaft length…it’s 1/4 inch SHORTER than the others…which means your pedal will feel really mushy/sloppy at best, and at worst, it won’t effectively stop the Jeep in emergency situations… not good!  So what I did to solve this little problem is simply cut the shaft about 1-1/2″ from the back end opening where the shaft goes into the booster, and then I got a piece of 1/2″ all-thread, welded it to the shaft and then welded a threaded 1/2″ coupler on the other end… now I have the ability to adjust it if it feels sloppy by simply taking the shaft off of the brake pedal and either turning it out or turning it in…beautiful!  Here are some shots of how it went:


After enlarging those holes on the bracket, it was pretty easy to fit the bracket on the back of the new booster unit:


The next step was to figure out where to cut the shaft, so I came up with the approximate location of where I wanted the coupler to end up:

booster-coupler-location booster-shaft-marked

Then marked that location with my sharpie and CUT IT!


Scary cutting a shaft like that…. YIKES!!  After I cut it, we did the welding… then screwed on the end…



…and it was ready to mount in the Jeep!

The last step before mounting, was to measure the distance from the bracket mount point to the eyelet of the shaft hookup hole on the original CJ and make sure the new shaft length was the same:



Ok, so it as 3-/7/8″ from the mounting surface to the center of the eyelet for the pedal hookup.  Time to duplicate that on the new shaft:



Ready to rock and roll now!!!   Now, MOUNT that bad boy!!!!



and hook it up to the pedal….(yes, I know I have to put the cotter pin in there still)


Then figure out the hard line connections


The new flare ends you need for this mod are supposedly the Weatherhead Part # 7917 and Weatherhead Part # 7912, but when I went to Napa Auto Parts and asked them for those… I bought them and brought them home and NEITHER were correct, so what I ended up doing was taking my booster unit AND my hard lines from the Jeep straight to Napa and had their guys figure out which ends I needed and they went ahead and installed them right there for me on my hard lines, making entirely new connections for them. I brought it home, and hooked it up and tightened it down and now we’re ready to rock and roll… All that’s left for the braking system now is to fix a leak on the passengers rear line, fill and bleed the system and run a new vac hose from the booster to the manifold.  This project is basically done.   This setup is a marked improvement over the CJ unit I had in there before… very glad I did this because with a little elbow grease I saved hundreds of dollars and now have a braking system that I feel confident in!

On to the Cooling System Upgrades…

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