Ford 8.8, disc brakes, porportioning valve question

I've installed a ford 8.8 with disc brakes in my 92 XJ. REALLY nice axle and pretty easy swap (not as easy as an XJ D44 swap - but both would have to have degree shims, or in my case cut and weld on new pads for the 6" lift and SYE/CV driveshaft angles).

Anyhow, my question is on the porportioning valve (just under the master cylinder and brake booster in the engine compartment). I haven't done any modifications to the brake system from that standpoint since I installed the disc'd 8.8. I have, however (previously) replaced the master cylinder and brake booster with one from a 97 XJ (larger booster, more omph and definitely made a difference in braking power over stock 92 stuff).

Should I have installed a different porportioning valve?

Also - there has been mention of a 'check valve' in the porportioning block on the XJs. A check valve needed for drum brakes, but if used with a disc brake setup it won't allow the pads to completely release pressure from the disc - shortning the life of the disc and pads. Has anyone heard of this as well?

Thanks in advance,

have u driven it? and used the brakes? do they work? if they work then drive it i never did anything to my brakes and they are bling bling!

stoney

I have a '97 with explorer brakes on a D 60 rear. I kept the stock MC and proportioner. I ran this with a stock front end for almost a year with no problems. The setup works just fine.
I now have a D44 front with Chevy 1/2 ton calipers and the pedal has more travel to it, but overall it stops better with 33's than it ever did stock.
Keep what you got until you find you are unhappy enough with it to start screwing with it.
mattk

i "fixxed" my prop. valve. removed the plug and pulled off the rubber o ring and reinstalled. Becareful of the spring that tries to pop out too. There are proper directions to be found I'm sure. I can nail the brakes and lock up all 4- 36" swampers make a neat sound.

Yeah - I've driven it several hundred miles on road, and 10s of miles on trail. The brakes work REALLY good (compared to stock - and compared to drums even with the 97 booster/master cylinder swap).

yellowxj: I'll do some digging around, but I haven't found a write up just yet for what you are talking about. I'm assuming the 'fixxed' you're speaking of is that check valve within the prop block - that is in there just for the rear drums (as drum brakes need to have a small amount of back pressure on them to keep the auto adjustment working correctly). I would like to do the same as you - as it will allow the rear discs to completely lax and keep from wearing out my rotors and pads (and lessen the chance that I'll warp the rotors).

Here's my interpretation of what you've said:

- you removed the rear brake line fitting that runs from the master cylinder to the proportioning block
- within the block after you removed the line, there is a plug and a rubber o-ring in there, remove those
- re-install brake line fitting
- bleed brakes

Am I correct in that interpretation?

There is no check valve in the proportioning valve. Removing the O ring or cup just means that it will run at a 50/50 split at all times not just under normal braking.
If you go to my site and the how to section you will find this mod written up in detail. Better to use a ZJ p/valve in my opinion

Thanks Mate!

I'll be trying the porportioning valve mod before this weekend's wheeling trip. I'll post my findings.

So far I have done nothing with the proportioning valve on mine, and all seems to work good. I also have a 8.8 with discs but I still have the 90 MC and booster. I am experiancing a low pedel but it seems to brake good, the rear will lock if need be. Hopefully when I install the WJ MC and booster I just got it will fix the low pedel problem. I know several others that have also left the proportioning valve alone too and it works fine for them too.

Tim