I'm looking for help with my 1979 ElCamino brakes.
The pedal must be pushed very hard to stop the car.
Brakes worked fine before I put another tranny in it.
Checked the brakes and replaced the front pads and one caliper.
Bled the brakes-same stopping problem.
Jacked up the car and applied the brakes.
The font calipers will stop the front rotors.
The back drums slowly come to a stop after pressing very hard on the pedal.
There are no leaks in the system.
I don't know if it's the master cylinder, power booster or the porpotion/metering valve.
Any help would be greatly appreciated.
Thanks,
Shrubby

I'd suspect that power booster as your problem. I'm thinking the trans swap/brake problem is a coincidence. Usually a hard pedal means lack of power boost...like when you try stopping the car when the engine's off and you're coasting to a stopping point.

Of course, I'd also may sure your rear shoes are adjusted perfectly...if they are too far from the drums, that would cause your slow stopping while you did the car-jacked-up test.

And...now that you've changed the front pads they will take a bit of time to seat, which means they will want higher pedal pressure now just because they're new.

Lastly, your worry about the proportioning valve is reasonable, except with all the other changes going on I wouldn't add that complexity into the mix at this time. Especially if the brakes were OK before. That means the valve was OK before...with the old set-up. I'd treat the proportioning valve as you do a carburetor. Don't mess with it until all the basics are covered first: fresh plugs and wires, new points, perfect timing, etc. So only after the brakes are working well would you want to fine tune them by changing the proportions. Good luck. Dave

My first question was "Was it doing this before you replaced the trans? Has this been going on for awhile or just suddenly started happening?"

When I got my 59 Elk it had a similar problem. Testing while up on jack stands revealed that the front brakes were working OK, but the back hardly worked at all.

I started gathering the parts to completely rebuild the rear brakes and discovered that one of the steel brake fluid lines on the rear axle had been pinched. The tube is on top of the axle, so I doubt it got crushed from being jacked up. The only thing I can figure is that someone loaded it on a trailer and chained it down with a come-along and crushed the tube with the chain. Or maybe they just hit it with a hammer. Whatever, it was flattened.

I went ahead & rebuilt the entire rear brake system but still didn't get very good results. The only thing I had not either replaced, cleaned, tested, examined etc was the flexible hose from the frame to the axle. I took it off and tried to blow thru it. Nothing.

I tried using compressed air to clear it. Still nothing. I tried running a stiff piece of wire thru it. Still Nothing.

I went to NAPA and got a new hose to replace it, installed it, bled the system. Problem solved. Apparenlty the rear brakes hadn't been working for so long that sediment had gathered in the hose & just petrified there.