I have read a lot of stuff about this Load Sensing brake prop valve. It is a great idea if it works. Mine does not.

I have adjusted it all the way down, all the way up (tied it to the frame). Reworked an verified function of the rear brake mechanicals. The brakes are adjusted and will self-adjust. My e-brake works great but I get very very little rear braking. If I am lucky I can get the rear wheels to lock up on ice.

Normal driving is not so bad but towing my boat is not so good. What goes wrong with these things and how do I check/rebuild/clean it out so that it functions correctly.

FSM section on the LSPV-BV

Do you have rear ABS?

On a side note, you don't want them to lock up before the fronts do, otherwise you'll be swapping ends pretty quick.

Yeah, a friend of mine rolled his Runner on account of rear brake lock-up, but then he was not used to the truck yet, was new to him.
I purchased a Wilwood manualy adjustable valve.
Will be installing it later this summer with new routing, etc.
I also can lock up the rear un slippery surfaces.

Thanks for the info. Mine is just way out of adjustment.

Many times they are sludged up internally and therefore inoperable. While the FSM shows them as being a non-serviced part, they are in fact easily disassembled and cleaned.