Boost and MC Options

[EUREKA]

I want to buy an upgrade brake booster and master cylinder. I see several options for this. I do not have good access to a junk yard or used parts so I am essentially forced to buy new parts.

 

Any thoughts on this kit,
Crown Automotive RT31037 Power Brake Booster Conversion Kit

 

 

 

[ghetdjc320]

I strongly recommend against that kit! I had it. Booster lasted about 18months before it started leaking. The master cylinder bore is far too big also and you’ll have trouble stopping with stock brakes. Here is some ideas to get you started: 

 

[EUREKA]

Thanks I'll avoid it. Unfortunately I am not yet aware of any off the shelf alternative.

 

All junk yard solutions seem to require work aournds for rod length or brake line connections. Not that I have any junk yards within hundreds of miles of me.

 

Great collection of info on that thread, but I don't see anything for my situation.

No links or recommendations on  boosters or MC.

[Pete M]

I imagine you can get a reman WJ booster from a parts store.    there are links to the dual booster swaps in the link in my signature. 

[EUREKA]

4 minutes ago, Pete M said:

I imagine you can get a reman WJ booster from a parts store.    there are links to the dual booster swaps in the link in my signature. 

Is that option better than the 95-96 XJ option? It seems one required shortening the booster rod and one requires making new lines between MC and combo valve..

I can't wrap my head around the pro and cons of all the different options.

 

 

 

[ghetdjc320]

A good functioning stock system works very well for most people if your on 31’s or smaller tires. The link above will help you get the most from any braking system including your stock one. 
 

For upgrade options:

 

An 01 XJ booster and MC is a good setup. I like that the XJ booster has an adjustable MC rod. You’ll need to modify the pedal rod as with all these non original options and also reuse the 1/4” spacer that is behind your oem booster. The washer bottle will move ahead about 3/4”.

 

The WJ booster also works well and doesn’t require a washer bottle move. You will need to modify the lip that is on the firewall just above the booster slightly. The accompanying MC is a 1” bore and works well. 

 

 

 

[ghetdjc320]

1 minute ago, EUREKA said:

Is that option better than the 95-96 XJ option? It seems one required shortening the booster rod and one requires making new lines between MC and combo valve..

I can't wrap my head around the pro and cons of all the different options.

 

 

 

You can get all the parts from rock auto for any of these swaps or you can hit up a local yard. I would recommend you stay with a stock system with a 15/16 bore unless your truck is used for towing or runs 33’s or larger tires. 
If you start modifying then you should update to either and adjustable or XJ prop valve. The WJ has some flex lines from the MC to prop valve that are easy to work with. Otherwise you will need to make your own lines and grab a couple of adapters. All the newer options (XJ and WJ) Will require a m10 and m12 bubble flare to 3/16 inverted flare. The rear output (m10 on the MC) is for the front brakes. The stock prop valve is really just a distribution block on an MJ. If you still have a functioning rear load sensing valve than you can just keep that setup but will need to go through the elaborate process of bleeding that system. 

[EUREKA]

7 minutes ago, ghetdjc320 said:

A good functioning stock system works very well for most people if your on 31’s or smaller tires. The link above will help you get the most from any braking system including your stock one. 
 

For upgrade options:

 

An 01 XJ booster and MC is a good setup. I like that the XJ booster has an adjustable MC rod. You’ll need to modify the pedal rod as with all these non original options and also reuse the 1/4” spacer that is behind your oem booster. The washer bottle will move ahead about 3/4”.

 

The WJ booster also works well and doesn’t require a washer bottle move. You will need to modify the lip that is on the firewall just above the booster slightly. The accompanying MC is a 1” bore and works well.

 

7 minutes ago, ghetdjc320 said:

8 minutes ago, ghetdjc320 said:

A good functioning stock system works very well for most people if your on 31’s or smaller tires. The link above will help you get the most from any braking system including your stock one. 
 

For upgrade options:

 

An 01 XJ booster and MC is a good setup. I like that the XJ booster has an adjustable MC rod. You’ll need to modify the pedal rod as with all these non original options and also reuse the 1/4” spacer that is behind your oem booster. The washer bottle will move ahead about 3/4”.

 

The WJ booster also works well and doesn’t require a washer bottle move. You will need to modify the lip that is on the firewall just above the booster slightly. The accompanying MC is a 1” bore and works well. 

 

 

 

Interesting. A good functioning stock system is woefully inadequate for me on ZJ's , XJ's and MJ's even on 31" tires. I mean it's fine if I have no load of passengers or cargo. Different strokes I guess. As far as modifying the pedal rod, you mean grinding the flat spot and enlarging the hole right? Doesn't the WJ booster also require modifying the lines between the MC and valve?

 

[EUREKA]

15 minutes ago, ghetdjc320 said:

You can get all the parts from rock auto for any of these swaps or you can hit up a local yard. I would recommend you stay with a stock system with a 15/16 bore unless your truck is used for towing or runs 33’s or larger tires. 
If you start modifying then you should update to either and adjustable or XJ prop valve. The WJ has some flex lines from the MC to prop valve that are easy to work with. Otherwise you will need to make your own lines and grab a couple of adapters. All the newer options (XJ and WJ) Will require a m10 and m12 bubble flare to 3/16 inverted flare. The rear output (m10 on the MC) is for the front brakes. The stock prop valve is really just a distribution block on an MJ. If you still have a functioning rear load sensing valve than you can just keep that setup but will need to go through the elaborate process of bleeding that system. 

I know I can buy any of these parts new/rebuilt ( in my case there is no local yard) the question is really which parts I want to buy.

Thank you for the excellent info. I do have the rear load sensing valve and was planning on making it adjustable. Should I keep it?

 

I guess I need to make a pro's and con's list for all the MC/Booster upgrade option out there.

[Pete M]

honestly, if I was going all out, I'd do one of the dual boosters, a front prop valve (from something with rear disks like a WJ), and then convert to rear disks and eliminate the rear height sensing valve.  if I found that it wasn't quite right, I'd add an adjustable aftermarket inline prop valve to the rear line to dial it in perfect.

[EUREKA]

1 hour ago, Pete M said:

honestly, if I was going all out, I'd do one of the dual boosters, a front prop valve (from something with rear disks like a WJ), and then convert to rear disks and eliminate the rear height sensing valve.  if I found that it wasn't quite right, I'd add an adjustable aftermarket inline prop valve to the rear line to dial it in perfect.

Makes a lot of sense.

What do you think about this kit for the rear,
https://leedbrakes.com/i-23439388-rear-disc-brake-conversion-kit-with-maxgrip-xds-rotors-dana-35-dana-44-chrysler-8-1-4.html

 

[Pete M]

I'm sure those are a great set of brakes, but whooooooweeee that's a big chunk of change for rears.    there's a writeup on using ZJ rear disks in the link in my sig.  Liberty and Explorer brakes are also common upgrades.

[ghetdjc320]

If we’re talking going “all out” run Wilwoods front and back with a mild hydroboost. I agree the stock ZJ system was inadequate with any sort of heavy use. But keep in mind how subjective everyone’s breaking experience is. Pads, rotors, vacuum leaks, tires ect all contribute to bad braking. I had a 98 ZJ 5.9 for years and also used it for towing. It was quite inadequate for towing for sure. Just not enough of contact area and the rotors were too small. Think about Jeep braking over the years: MJ single diaphragm 8” booster with 15/16 MC. If you engine vacuum is good and all components are working as oem intended, it was a system that could easily lock up 31s. Throw in a worn out engine, crappy hard compound pads and no pad break in (few people even know they need to break in their pads) and you get bad brakes. In ZJs stuck with the same front brakes but added rear disks and upgraded the booster. XJ upgrades the booster in 95 with a dual 8” and, with the newfound assist, increases the bore to 1”. WJ has essentially the same MC and Booster in terms of performance but updates to a dual piston front with about a 20% increase in piston surface area iirc. Larger rotors and more swept ultimately is the biggest improvement here. 

[EUREKA]

3 minutes ago, Pete M said:

I'm sure those are a great set of brakes, but whooooooweeee that's a big chunk of change for rears.    there's a writeup on using ZJ rear disks in the link in my sig.  Liberty and Explorer brakes are also common upgrades.

Yes I know. If I could just drive over to a wrecking yard I would absolutely be doing one of those upgrades. Nearest one is 152 miles away.  I suppose I could order new/rebuilt version of the parts involved in one of the swaps.

[ghetdjc320]

16 minutes ago, EUREKA said:

Makes a lot of sense.

What do you think about this kit for the rear,
https://leedbrakes.com/i-23439388-rear-disc-brake-conversion-kit-with-maxgrip-xds-rotors-dana-35-dana-44-chrysler-8-1-4.html

 

Rear disks do not increase your stopping power unless you go with big calipers like a Wilwood kit. Don’t get me wrong though, disks are so much better in many aspects. If you want disks in the back but aren’t going to upgrade to a 4 piston front then go with these: https://www.shop.blackmagicbrakes.com/Dana-44-Rear-Disc-Brake-Conversion-Kit-Dana-44-Rear-Disc-Conversion.htm

That being said, until you take care of the rest of the system you will not see an improvement in braking.

[EUREKA]

My friend told me today that his friend dropped off a ZJ at our local mini-wrecking yard two days ago. That would be their first jeep of any kind in more than 3 weeks. I need to call tomorrow(Monday) and see what's up with it.

[EUREKA]

1 minute ago, ghetdjc320 said:

Rear disks do not increase your stopping power unless you go with big calipers like a Wilwood kit. If you want disks in the back but aren’t going to upgrade to a 4 piston front then go with these: https://www.shop.blackmagicbrakes.com/Dana-44-Rear-Disc-Brake-Conversion-Kit-Dana-44-Rear-Disc-Conversion.htm

That being said, until you take care of the rest of the system you will not see an improvement in braking.

 

I understand. I do find not having to adjust them nice. But I plan on improving the front brakes as well. I was considering this,

https://www.rustysoffroad.com/rustys-wj-steering-and-brake-system-xj-tj-zj.html

 

I notice that black magic kits says will not work with XJ Dana 44. I have a Dana 44 in this Comanche, its a metric ton edition.

 

 

[ghetdjc320]

8 minutes ago, EUREKA said:

 

I understand. I do find not having to adjust them nice. But I plan on improving the front brakes as well. I was considering this,

https://www.rustysoffroad.com/rustys-wj-steering-and-brake-system-xj-tj-zj.html

 

I notice that black magic kits says will not work with XJ Dana 44. I have a Dana 44 in this Comanche, its a metric ton edition.

 

 

Most people on almost all the Jeep forums will tell you to stay away from Rustys. Not sure if you read through the post we linked here earlier but there are several options if you have the 89 and earlier Dana 30 front knuckles. They are all linked there. All the rear disk kits your looking at are not going to fit the xj/mj d44 our if the box. The pre 90 Dana 35’s and the xj/mj 44 have a different flange and some require a spacer to retain the axle bearing since they are pressed into your axle shafts. They can all be modified to fit though. You have to think about how much your willing to spend on brakes. You can easily go down a 2-4k rabbit hole. 

[EUREKA]

13 minutes ago, ghetdjc320 said:

Most people on almost all the Jeep forums will tell you to stay away from Rustys. Not sure if you read through the post we linked here earlier but there are several options if you have the 89 and earlier Dana 30 front knuckles. They are all linked there. All the rear disk kits your looking at are not going to fit the xj/mj d44 our if the box. The pre 90 Dana 35’s and the xj/mj 44 have a different flange and some require a spacer to retain the axle bearing since they are pressed into your axle shafts. They can all be modified to fit though. You have to think about how much your willing to spend on brakes. You can easily go down a 2-4k rabbit hole. 

Yes I have heard of their reputation. I'm in a tough situation on parts availability.

Yes I did read through the post you linked. I guess I could steal the knuckles from my 88 MJ but this project is a 91 MJ.

Yeah I see you are right, none of these will work for my dana 44.

I am FAR more concerned about time right now than money. I will gladly pay for easy bolt on options.

[ghetdjc320]

6 minutes ago, EUREKA said:

Yes I have heard of their reputation. I'm in a tough situation on parts availability.

Yes I did read through the post you linked. I guess I could steal the knuckles from my 88 MJ but this project is a 91 MJ.

Yeah I see you are right, none of these will work for my dana 44.

I am FAR more concerned about time right now than money. I will gladly pay for easy bolt on options, though it seems none exist.

For your rear axle you already have 10” drums that are quite decent if your in a time pinch. Do the wj or xj swap then and if you have a good functional real valve you can keep that setup or remove that system and run an xj prop valve or an adjustable Wilwood one. In my build thread I documented the swap a few weeks ago

[EUREKA]

I'll check out your build thread.

 

[EUREKA]

This kit does seem to have the required parts to work for the MJ Dana 44.

https://teraflex.com/shop_items/528ffa7fead962f416e72f53

 

Mentioned by HOrnbrod on this thread,

https://comancheclub.com/topic/28034-mj-d44-zj-disk-brake-swap/

 

[EUREKA]

AS far as Booster/MC, I think I'm going with a 95-96 XJ booster and mc route.

 

[ghetdjc320]

Let’s clarify a few things here. The kit that fits 90/91+ d44/d35 and 8.25 will NOT bolt on to original XJ/MJ D44s. It can be modified to fit but it’s basically just a set of d35 ZJ backing plates with Exploder or ZJ rotors. Treadles does make a kit that is supposed to be bolt on for earlier model D35’s and D44s. Non c-clip d35s (89 and earlier) and XJ and MJ D44’s have the same mounting flange pattern. TJ d44’s and 90+ D35s as well as 8.25’s share the same flange pattern. The ZJ backing plate has to be slightly enlarged for the tj d44 and the xj 8.25. Easily done with a dremel. Also as @Garvin mentioned, you’ll need a press and might as well replace the axle bearings and seals while your in there.

Just remember, your really not gaining any additional braking power when going to an exploder/ZJ caliper and rotor setup. I’d look into doing at least a dual piston caliper with 12” rotor for all the work it entails. The ZJ rear disk setup is an easier swap on  the newer d35/tj d44 and xj 8.25. 
Here is some info on the variations of the teraflex kit:

[bval]

15 hours ago, ghetdjc320 said:

I strongly recommend against that kit! I had it. Booster lasted about 18months before it started leaking. The master cylinder bore is far too big also and you’ll have trouble stopping with stock brakes.

 

I agree with @ghetdjc320. I have that kit in my truck right now and I have the big 4 piston Wilwoods up front, with the stock metric ton 10x2.5" drums out back (but recently refreshed) and the bore is still too big. I'm going to rear discs in the near future and if it's not better with those, I'll probably go down to the 1" MC (but keep the booster).