After seeing alot of misinformation spread around numerous threads regarding how this little piece of metal on the rear frame works, I thought I'd post up some info. One of the most popular misconceptions is that the brake line going from the LSPV to the "T" near the passenger front wheel some how redirects pressure from the rear to the front brake circuit. How does the LSPV move fluid from the rear brakes to the front, to an area with higher pressure, without a mechanical pump? the line going to the front brakes is only used for "pressure sensing" in case of front brake failure - here's some reading on how proportioning valves work, scroll down to pg 13

here are 2 screen shot from the link above



Here's the Field Service Manual for the Brake System on a '93, but not much changed in over a decade - the system is essentially the same
and for anyone thinking of getting rid of the LSPV, Here's my write-up - look at post 18

 

those things are finicky when i did my leaf swap i teied it up and cut off the rest and have it tuned pretty good.

 

thanks for the info and link to a reasonable proportioning valve.