lets talk brake proportioning valves
 

I found a set of Dana 35 Disc brakes on ebay for a fair price. I am going to clearance the axle hole and install them on a C8.25.

I have read much detail about the install, but it is rare to find info on how the proportion valve affects the braking. In theory the OEM valve in my 2001 XJ would cause the disc brakes to lockup in sketchy weather.

The two solutions I have read are:

1) Use the GC prop valve. This does not come with my ebay kit, but I have seen them for $50 on ebay.

2) Remove the prop valve gasket from the plunger to equalize the f/r brakes. This was a writeup on Naxja.

Has anyone done option 2?

Has anyone just left the prop valve in the OEM state and driven it as is? If so, how was the handling in wet/snow/offroad, etc.?


I'll have the kit in a week, so I have time to iron out some of the issues beforehand.


Thanks,


K

When i did my conversion in my 98' I left the stock prop valve the way it was. initially I did notice that the rears were a bit touchy but I attributed that to having more stopping power. I have noticed they do seem to drag a bit sometimes (especially when backing). I am planning on changing to a grand cherokee prop valve soon as I have time. I would not reccommend taking the valve gasket out as that eliminates the front/rear brake circuit isolation, which is a bad thing (if you get a leak or hole anywhere in the system you loose all brake pressure). I would just use the prop valve that is for a 4 wheel disc setup and call it good. Also the XJ's dont have a residual pressure valve. That only applies to vehicle that have the master cylinder mounted at or below the level of the brake caliper (I know that wasnt part of your question but if you read through alot of the threads on the conversion that topic seems to come up alot). Hope that helps!

I used GC discs on my d44. What I ended up doing instead of using the whole prop valve I just used the spring, and the brakes would lock up 33's, and hold my rig with my 2 cases in double low first gear at idle.

here is a pic of the springs.. one on left is gc.. one on right is stock xj

http://inlinethumb02.webshots.com/42...600x600Q85.jpg

Looks like the GC spring is shorter by a few MM. Is it also stiffer?

Point being, could I shorten the XJ spring?


K

Thanks for the info on the gasket. Sounds like pulling that off is a dangerous thing.


K

Definately stiffer.. not sure I would try cutting down the xj one. It was just easier to swap the spring instead of the whole prop valve

Does it matter what year Grand Cherokee you use for the Proportioning Valve Spring? I just did the Terraflex disc brake conversion on my 89' XJ. I would like to try replcacing the spring and see what happens.

All GCs had rear discs, so any ZJ one works fine.

Did you up grade your booster also ?

I have not yet. I definitely want to upgrade the booster. I have several detailed write ups on hand and it looks like the 96' booster is the way to go. I just need the time. At this point I have not felt a noticeable change in the braking characteristics with only the disc brake conversion.

I think 93s had rear drums.

I snagged the guts out of a 94 to 98 GC prop valve and swapped them into my 88s prop valve.