[dennislbrooks]

I have seen answers on both sides of this. As I understand if with disc disc front and rear are evenly matched, no proportioning valve is required. On our custom setups this is probably unlikely but how would you know exact proportioning needs unless you test with emergency braking on good traction to see when the rear wheels lock up first? What about poor traction?

Hence ABS was invented, On my 67 which has 4 wheel disc I have an adjustable proportioning valve but doubt if it it set for all/best situations. I suppose if all wheels lock at the same time, it may be close without abs. This truck also has Hydroboost.

I would want to keep the shutoff valving for front or rear pressure failure that is in a proportioning valve or in a distribution block like in a stock 60-70 (maybe) but this may be in your 2009 setup.