Looking for a Brake Pressure Differential Valve
 

Hey everyone! My first thread in this forum, but definitely not new to FTE.

Looking for a Brake Pressure Differential Valve part number C8TZ 2B257-D for a 68-72 truck with 4 wheel drum brakes.

Any of you who have pulled it off when you upgraded to front discs and still have that valve, I'm interested in getting it from you.

Please PM me if you have one you'll part with.

There is a rebuild kit with the o-rings needed to fix the valve, available from Muscle car research. I fixed mine and it is fine now.

KOT390

He doesn't already have the brake valve since he has a '65 F250 --tandem MCs and pressure differential valves didn't come out until 1967. He's looking to add one to his truck because he's installing a tandem MC to replace the single pot MC he currently has.

^^^What Steve said ^^^ :-blah

If no one has one lying around, I do know where a '68 F250 with all wheel drums is, in the wrecking yard (I had robbed the single diaphragm booster/mounting brackets off of it a few years ago). I highly suspect the brake valve is still on the truck. It would probably need to have new seals installed, since it's been sitting in the same spot for years but, it should be a rebuildable core.

That's a fantastic offer Steve and I would appreciate it. Please PM me what you need to do this for the part, labor and shipping. Looks like you're about 1,000 miles from me. I'm in zip code 22801.

Of course, we should wait until others have responded, in case they already have one in hand. But I'm thinking these valves may be made of unobtainium.

I have not purchased the new master cylinder yet, so this doesn't have to be done immediately (not that I expect that anyway).

I'm just trying to get my ducks in a row before I start messing with the brakes on a driving truck. Since you're the one who told me about the valve in the first place, you know I still need to wire the switch/light in besides redoing the brake lines. And I'll need to figure a way to hook in a tee for the brake light switch. I saved the info on the valve rebuild kit from Muscle Car.

I understand. I like to gather all my parts up before adding/converting something over on my truck as well.

Personally, I don't know anyone with a pre-67 truck that's installed the brake warning light along with installing the pressure differential valve --although, it would probably be a good idea to take the time/effort to install the warning light/wiring along with the safety function of the PDV.

As to the wiring; I'm not sure if the ignition switch on a '66-earlier pickup has the Prove Out contact circuit in it, to do the self-test of the brake warning light, when the key is turned to the "Start" position when using a '68 or later valve pressure switch (?)

If the '68-later ignition switch is needed and if it's compatible with the '66-earlier wiring harness and the hole in the dash, then, it would be needed to make this feature and the warning light function as it should.

Hmmm... This is starting to get complicated. Since I've never seen anything regarding the Prove Out function before you mentioned it, I have to assume the pre-67 trucks did not have it.

Maybe I'll just skip the valve addition and go with a simple dual chamber m/c and add a brake light switch.

I really appreciate all your input. You are apparently the brake expert here.

Aaahhh. Right. Sorry, I missed that :o

Easy to miss since I didn't state it. Just have my avatar to go on, and that's not a description of what I wanted to do.

Does this rebuild kit work for the -D valve which is for drum/drum though? Has anybody actually installed it on their '68 and up F250 2WD with drum brakes on the front and drum brakes on the back? the o-rings fit?

I did the Ultra brake upgrade. Mine is still under my truck if you get in a pinch...

Chris, I really appreciate your offer to take the one out of your truck. It's not a 67 is it? That brake system is apparently a one-year deal. EDIT: I just looked at your gallery pics and I think that's a 68? I know next to nothing about the newer trucks.

I may ask you to get that off your truck but I'm in a bit of a quandary right now. I have to decide if I want to figure out how to include the Prove Out circuit Steve mentioned before I continue this quest. The idea of a warning system is appealing, but I'm ignorant of whether the later ignition switch will work in my 65. I may just change the m/c and leave out the brake PDV. :-X19

My truck is a 69. I do have a 78 laying around, but I dint think that will help you. I understand what Ultra is saying, but I don’t need a light to tell me my brakes aren’t right. Just saying...

Technically, there may be different engineering numbers on the Bumpside F100 through F350 pressure differential valves but, the internals and operation of them are all the same --they're just looking for balance (or, imbalance) in circuit pressures.

The only difference between a '67 PDV switch and a '68-up PDV switch is that a switch for a '67 has a 1-wire connector and a PDV switch on a '68-later valve is a 2-wire configuration.

The two switches are interchangeable between the '67 valve and the '68-up PDVs --provided you have the correct wiring connector to plug into the switch.

The '67 switch would require a 1/2" end wrench/socket to remove/install it on the valve body. The '68 - later switch would require a 9/16" end wrench/socket. Both the '67 and the '68-up nylon pressure switches have a 3/8"-24 threaded base on them, where they screw into the valve body.