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Discussion Starter #1
I am getting my new axles in a week or so for my TJ. Disks up front will be off a K series Blazer. Disks in back will be SVOs off mid 90s Explorer. I was told by the guys making the axles that all I need to do is take out the spring in the rear proportioning valve and this will allow equal pressure to the back and front. Is this all I really need to do to have great brakes? Is there any other solutions? Does anyone know of a hydro boost system that I can fit on my TJ? Thanks.
 

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Generally the TJ has a combination valve which has more function than just rear proportioning. Rear proportion is a function of the combo valve. Not that it really matters in your case.

They are correct in that you can remove the seal from the plunger in the front portion of your combo valve to eliminate proportioning front to rear.

There is what looks like a large bleed screw on the grill end of the combo valve. Unscrew it and don't lose the spring. There is a brass plunger with a black seal on it. Remove the little seal and reassemble. Bleed the brakes and you are ready to go.

Your proportioning will now be done by the physically smaller size and smaller clamping pressures of the rear caliper.

If you have difficulties with generating enough volume for the fronts, you can swap in a ZJ master cylinder. Bolts up to the stock booster and has a step bore for the larger front calipers. Front is 34 mm and rear is 24 mm.

This set-up will generate around 1200 psi line pressure using the stock booster, which is usually sufficient for most calipers
 

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Discussion Starter #3
Does it matter what year ZJ? How is it that the new master cylinder doesn't also require a different booster? I thought there would be problems not replacing both.

Also, the guy doing my axles said to take the spring out of the proportioning valve and discard it. He said to leave the plunger and stuff in there and just let it float around. Does this make sense?
 

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I just picked a year that had 4-wheel discs on it.

I have not played with the valve enough to know which part does which. I just took the seal off of mine and reassembled it. Seems that either should work.

I am only giving you info that I have direct experience with and have done.

That is why I posted the line pressure generated by the stock booster. I did the line pressure check myself. That is what is generally needed to make calipers work, and if the stock booster does that, why change?

I looked at the zj booster and it appears to be the same diameter and depth, given this, I doubt there are any significant differences between the two with the exception of valving. Pressure is controlled by diameter and number of diaphragms. The TJ booster is already a high gain booster with dual diaphragms.
 

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Discussion Starter #5
Thanks. I will just hook it up as you described. Then I will see if I need the larger master or not. I better start looking for one just in case.
 
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