Where is the residual valve in a '77 Ramcharger? Is it in the master cylinder or the proportioning valve?

I've had a brake issue on my Ramcharger since I swapped in the front Dana 60 (brakes were good with the 1/2 ton master cylinder and front 8-lug Dana 44). When I swapped in the Dana 60, I also swapped the proportioning valve and master cylinder from the donor truck ('85 W350). Both axles still have the stock front discs and rear drums.

No matter what I did, I always had a lot of pedal travel. Braking power was always good, the pedal just travels a lot further than it should. It pumps up just slightly (very slight), but the brakes have been re-bled countless times. The booster push rod was adjusted so the master cylinder would erupt inside with about a 1/2" of pedal travel. If I adjust the push rod longer, it reduces the pedal travel greatly, but the front brakes end up dragging badly and I have to shorten it again. There is no in-between adjustment.

I thought I had a bad residual valve in the master cylinder, so I installed a remanufactured 1 ton master cylinder and brake booster. The problem still exists. Braking power is phenomenal, it'll easily lock all 4 tires, but the pedal has to almost travel to the floor to get the braking power. Again, I've re-bled everything, I'm confident that there is no air in the system.

Do I need to replace the proportioning valve? Will my 1/2 ton proportioning valve work with the front 60?

My 75 had a residual valve in the master. You need to pull the cone at the port. Starting a metal screw and pulling it back worked for me. I also used a newer brass prop/shuttle valve. Newer 1 ton truck application.

So, if the residual valve is in the master cylinder, what is causing the excess pedal travel? Or did I get two bad master cylinders in a row?

There should be no residual valve in your system. They did away with them in the mid 70s, and all of your stuff is newer. A residual valve will have no affect on pedal travel anyway. If your travel is too long, I would think your master cyl has too small of a bore. Not enough volume to actuate the brakes and still have enough in it to keep the pedal off of the floor. Be sure your front wheel bearings aren't loose, and your rear shoes are adjusted up. Adjust the pushrod on the booster so it almost touches the piston in the master cyl (you might do this with the truck running, in case the vacuum causes the diaphram to move a bit). I would personally do away with all of the stock valving. Remove the safety switch, stock proportioning valve, and hold-off valve if so equipped, and then install an adjustable prop valve in the rear line. Adjust it and forget it.
Travis..

residual valve (http://www.stockcarproducts.com/residual.htm)
some related info (http://www.championtrailers.com/remove_residual_valve.htm)

Hey,

You can have the 1 ton PBB and MC out of my truggy for free if you want them. They only have 5,000 miles on them and no problems out of them what so ever. Might be worth trying, or keep it as a spare.

I'll be hauling the rest of it off in a couple of weeks so if you want them they're yours.

FWIW if it has wheel cylinders there is a residual pressure valve in the that system...

there should not be one on the disk side....


chris:cool2:

It is my understanding that when Chrysler started using the metal backed piston cups in their wheel cyls, they did away with the residual valve. The metal backer put enough tension on the cup to keep air from creeping in. This is the way I understand it, though admittedly I don't really mess too much with later model Mopars.
Travis..

It is my understanding that when Chrysler started using the metal backed piston cups in their wheel cyls, they did away with the residual valve. The metal backer put enough tension on the cup to keep air from creeping in. This is the way I understand it, though admittedly I don't really mess too much with later model Mopars.
Travis..


this is possible i guess, i too havent had to get that deep in the later model stuff... (this is how we learn right?)


chris:cool2: