Need A Brake Upgrade For 79' Chief...

[Rompn]

Basically I now have no brakes. Before it was so so but now nothing. I heard on the list before that you can upgrade things like the power booster to a dual diaphram booster. I would like to do this conversion. I am going to replace everything (Booster, master cylinder, fluid, pads and shoes). I need to know what year dual diaphram booster will work on my 79' Cherokee Chief. I think someone said that a 77' J-10's will work? I'm not sure though. I need to get this done in a hurry to because I am taking the Jeep to the lake over Memorial Day Weekend and I need brakes. Anyone know if there are any other upgrades you can do on the brake system as well? Thanks.
Pat
bmxtrme@aol.com

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INNOVATIVE FABRICATIONS
79' Cherokee Chief W/T
360/TH400
Jacob's Pro Street Ign.
31x10.50x15 Fun N'Mud's

[Michael F]

The 77 J10 booster is single diaphragm unless sombody has installed a double for a J20. The 79s use a cast iron master, you can use any year double booster that uses a cast iron master. The aluminum master style will not work.

The double diaphragm booster is a couple inches thicker than the single.

You will also need to make sure the whole system is in good shape so you do not blow out a brake line that has badly rusted.

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81 Cherokee Laredo WT
56,000 orig. miles (not the engine I6 to V8 conv.)
360/727/208/3.31w/tracklock/35x12.5 ProCompMT/double diaphragm brake booster
4" BDS lift/TrailMaster SSV shocks
79 Cherokee Chief WT (snow plow)
360/400/QTw/LR/3.54/31x10.5

[Rompn]

So what year would I want to get that would use a double diaphram booster? Will a 79' J-20 brake booster work? Also, I was just planning on using the stock 79' Cherokee master cylinder with the dual diaphram set up unless there is some kind of upgrade for the master cylinder? Maybe running a J-20 or J-30 master cylinder will increase capacity and braking power? Also, I don't think an aluminum master cylinder was offered in 79' right?
Pat
bmxtrme@aol.com

------------------
INNOVATIVE FABRICATIONS
79' Cherokee Chief W/T
360/TH400
Jacob's Pro Street Ign.
31x10.50x15 Fun N'Mud's

[Michael F]

The TSM says the Wag and J20 masters are the same. You can call the parts places to make sure.

The aluminum master did not come out until posibly 80 and I know 81 for sure. The 81 master also has a quick take up valve that may not work with the older calipers.

For the price I would replace the master cylinder. The masters can get a worn spot where the pistons ride and when you can push the brake pedal further easier you will be working outside of this worn spot and can damage the piston seals as they are pushed over the edge from worn to the new part of the cylinder bore.

[Rompn]

I don't have a Wag though. Also, will a 79' J-20 brake booster work?
Pat
bmxtrme@aol.com

------------------
INNOVATIVE FABRICATIONS
79' Cherokee Chief W/T
360/TH400
Jacob's Pro Street Ign.
31x10.50x15 Fun N'Mud's

[Michael F]

The 79 TSM says the Cherokee/Wagoneer and J10/20 use a master cylinder with a 1.125" bore, this sounds like the same master cylinder.

I have only been able to look at one J truck to compare brake rod length to my Cherokee (both installed) and they looked to be the same. I could not find a good used J20 booster so I used a booster from a 3/4 ton chevy van. The booster had a longer brake rod and it had to be shortened to work in the Jeep. The boosters in the Jeeps are a chevy unit and are identical to the chevy trucks except for the brake rods.

So yes a 79 (or older) J20 booster should work in your Cherokee. If you buy used you need to make sure the booster is good by seeing if it will hold a vacuum for at least several minutes.

[Rompn]

Mike,
Thanks for the help. I am running down to Kragen right now to order my new 79' J-20 Brake booster.
Pat
bmxtrme@aol.com

------------------
INNOVATIVE FABRICATIONS
79' Cherokee Chief W/T
360/TH400
Jacob's Pro Street Ign.
31x10.50x15 Fun N'Mud's

[Mike D]

and how about a 60'ys fsj... i would really like a booster now for my wagoneer

[Sitting Bull]

Originally posted by Rompn:
I don't have a Wag though. Also, will a 79' J-20 brake booster work?
Pat
bmxtrme@aol.com

.
Yes, this will be a direct bolt-in, I used the same year swap for mine. HELPFUL HINT: On the back of your existing booster there is an adaptor bracket, make sure you remove this bracket before turning it in as a core. You will need it for the new booster as well. Several people have forgotten this, and it will cause a big headache.

[turtlejoe]

FWIW I installed a 79 J20 dual on my 78 Chief - straight swap, although the booster is thicker than the stock one was. This however did not cause any fitment problems. Nice improvement in my braking.