Reply to "Tasks Required if proportional valve taken out"

The stock non-adjustable proportioning valve was designed for hard belted-bias 185-70x 15 front tires & 205-70 x 15 rears. If you are not running those tires & sizes, the valve- if it still works- is set wrong and cannot be changed. Replace w/a modern manually adjustable valve to see it you really need one, especially if connected the factory way. Most braking is done with the fronts and the stock prop-valve plumbing limits pressure to the front brakes, unlike every other car on the road that I know of.

The shuttle valve often builds up varnish in the areas at each end of the shuttle's bore. Then when brakes are bled or something else happens to drive the shuttle into the unused areas, it sticks and has no return springs (like other cars) to push it back to center after the problem is fixed. A shuttle stuck at one end of its travel stops about 90% of fluid flow to the two brakes on that end of the car- a VERY dangerous thing!

Sometimes the shuttle can be blown back to the center with air pressure (very sloppy!) but most often it takes complete removal from the car and disassembly to re-center the shuttle. It's function of lighting a red warning light on the dash is compromised by 'other' functions- if the e-brake handle is slightly pulled, the same light lights, as it also does if you have brake pads with grounding wires attached to the chassis and the pads get thin. So when that red light lights, you must search among the 3 possibilities to find the real reason. Not worth the effort IMHO- a good owner will inspect pad thicknesses & brake fluid levels periodically, and not drive if the e-brake is partly on. I dumped the OEM shuttle and prop valve from our '72 in the last century and have not missed either.