brake issues help!

[darksaga]

I have a 68 gmc 3/4 ton pickup with a 73 front axle and a dana 60 rear I bought the truck a few weeks ago knowing that the brakes had problems.

I thought the reason was that it had disc brakes and still had a drum master so I bought a a new (not rebuilt, raybestos) master for a 71 (interchanges with a 73) (morine), I installed it but the booster pushrod stuck out way too far so I cut it (bad Iknow bad), problems was far worse.

I bought a rebuilt napa booster for morine brakes but the pushrod to the pedal was too long........ so I started to hunt junkyards for a mounting bracket that was longer coulden't find one. I look on ebay and there was a booster and bracket, bid win install.

that brings me to today I put everytthing back together but the pedal still sinks to the floor with the truck running I adjusted the pedal rod all the way out.

the calipers and ruber hoses for the front have been replaced (one of the bleeder screws broke) and I checked the back wheel cylenders for leakage.

I am running out of options, the master may be reversed I installed the front brake lines to the front (small resivor) and the back lines to the back of the master (huge resivor). My dad thinks it may be the prop valve or the rear drums may need to be adjusted

[raceman6135]

I'll admit right away that I'm not sure what the early Chevrolet trucks need in the way of booster/master cylinder, etc., but on all the vehicles I've seen, the disc brakes need the larger resevoir, usually located at the front of the m/c.

The drums take much less volume, hence, they use the smaller capacity chamber.

If you are trying to activate front discs with a small chamber, that could be the first of your problems.

Sorry I couldn't help re: rod length, booster selection, etc.

DJS

[darksaga]

I think that's what the problem is, on my chevelle the larger line with the larger flare nut goes to the back breaks and the smaller line goes to the front but the resivor is bigger for the front. The chevelle is 4 wheel disc now and its the same way, as whjith my all wheel drum duster. I am going to swap the lines tonite after work with a set that I found in a junkyard alond with the prop valve. T rear drivers side self adjuster is frozen too so that can't help. I am not looking forward to pulling the rear drum again! (full floater axle)