Are they the same?

[krue]

I was looking at a 72 proportioning valve and a 75 proportioning valve and the only difference I could see is the 75 had an extra line coming out where the 72 had a plug. Other than that they were identical externally.

[tnblazerk5]

i have no clue i changed all my stuff out to newer 1980 stuff

[FormerMember]

The only differences I've found so far is in the rear circuit. Make sure you get a disk/drum or disk/disk if you need one.

Otherwise, it seems to be one big chunk of brass through the years that had them...

[Tx Firefighter]

Board member Matt67350 taught me a neat trick, Krue. He uses a complete late model lines, valve, and everything from the donor truck. Even though they appear drastically different, they all bolt straight in.

The 72 had the prop valve mounted under the master cylinder, while the later trucks mounted it down low on the front of the frame. He uses it all, and says the proper holes are already in place on the early trucks.

I've seen it done on his trucks and it looks very nice, much nicer than a 72 style setup is.

[krue]

That's the way I was going to do it when I was still planning to use the crossmember from the 75, but now I'm planning on using the plumbing and the spindles from the 72. I'm holding the xmember against the time I can rebuild it and purty it up.

[Tx Firefighter]

Interesting discussion here...

I'm not following you completely. I don't see where the crossmember's vintage will affect your brake lines. The later model stuff runs along the frame, to the little front under the radiator corssmember and then out to the framerails. The hoses, mount to the frame rails in front of the upper control arms.

I can't see how the crossmember affects this.

[krue]

I'm not pulling the engine to swap just the spindles (I was pulling it for the xmember swap), so I'm thinking it will be easier to get the 72 brake lines under it. Or I could be totally out to lunch.