chrysler mini vans used to have them on the rear axles so did some of the lighter FWD cars that used discs all around . they tried them on ford ranger pickups in the late 80's and had some problems with them trying to get them to work right they were too sensitive and still allowed the rears to lock up with no weight in the bed , they discontinued there use . when ABS came out they all but disapeared . have to watch the linkage for binding and length , if one of the rods get bent it messes things up . and also the position on the axle is another thing to look at . as if you offset it bodyroll has a effect on how it will work . have to mount it in the roll center point of the axle
Isn't it ? Front dives in hard breaking and weight transfer unloads the rear. It's sort of an unintendend use I guess. It's supposed to let the rear brakes work better on a vehicle when its carrying a load. Yeah, I've seen them hooked up a few different ways. Its always been 1 valve, 1 mount, 1 linkage rod, and 2 lines. My thinking goes to 2 valves, 2 mounts, 2 linkage rods, each with 1 line to deal with body roll. Most traction gets the most brake.
you could try it but if more than likely your going to upset the balance of the vehicle and might roll it over from over and under braking , most of the oems got away from this valve with ABS but some did it by going to a diagonal braking system this way the pressure was more even , and it pulled straight if you lost a side . I would mount it on the top of the pumpkin that way it will evenly control both sides at the same time even on RWD the front discs supply 70% or more of the braking power , My O/t C3500 chews up front brakes , but the rears because they do not self adjust ( murphys law of self adjustment , anything that is supposed too doesn't )
I deal with a lot of Toyota pickups they have used them on 2&4 wd trucks and they work real good but when you modify the suspension you have to change the rod . At times on jacked up trucks It is sometimes trial and error in that it is not proportional to the lift .The Toyota ones cannot be repaired they must be replaced when they leak.
There's 1 on the back of my crew/dually , you can feel the difference in braking when we put the 3K lb. truck camper iin .. so it does work . dave
I never owned a vehicle with one, but worked and tested many vehicles that had them. They became necessary because of ever tightening DOT braking requirements in the '70s, and initially used mainly on trucks because of the drastic F/R weight changes from empty to loaded, but gradually on many front drive cars and mini vans. ABS systems eventually made prop valves obsolete, but was in it's infancy and many years away from reliability and normal production until the 90s.
The reason OEs went to diagonal split braking was to comply with DOT braking requirements when front drive vehicles came about in the '80s. Front drive F/R weight distribution is mainly on the front axle, so with the standard vertical split hydraulic system, a large rear brake was not needed. But, DOT requires split system testing, and a small braked rear axle would not p*** stopping distance testing. Diagonal plumbing, however, allows one smaller/cheaper rear brake along with one large front disc to easily p*** failed systems testing. (The rear brakes still have to be able to hold the vehicle on 20/30 % parking brake grade tesing). Diagonal braking was (and may still be) used on some vertical split rear-drive vehicles, where a large enough rear brake was/is not available to qualify for DOT. Extended length limos is one example I worked with. Driving an early diagonal split system during failed system testing could be a real handful, but over the years improvements in suspensions and ch***is design resulted in much improved handling when one system is failed.
I have an extra mini van bouncing around over here. I'm gonna play with it and see what's up, and if that valve might have any use on a hot rod. The load difference won't be as big as a truck but that's a linkage ratio thing.
Keep in mind load sensing valves were designed for specific vehicles, complicate plumbing, and are a real pain to set up in a custom ch***is. An adjustable prop vale is a MUCH better choice, especially in a vehicle that does not have a high percentage of weight transfer empty to loaded, like a normal street/hot rod. Not trying to burst your bubble, jmo, based on a lot of experience.
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