[daveinluray]

a bit old but as i search this thread is most recent. I am finding that the valve in question is called a combination valve(per service manual). this seems to indicate that this is another name for proportioning valve?
Please correct any thinking here as I am trying to get my head around doing my brakes correctly and safely.
It is my understanding that with front disc and rear drums the front need to be limited until the rear brake can overcome the pull back springs.

my truck is missing its valve and I have purchased one online new. Problem is it has an extra port (two) for the front. Can I plug one or should I get a different combination/metering valve?