[importsmasher]

I just got my 74 GTO running, and have not driven it anywhere but onto a trailer (see the topic "another 74 GTO back to life)...as I drove it out of my driveway, when I hit the brakes, the rears lock up hard, then slowly release....This isn't an issue I have had before. Could it be the brake booster? I am not sure the front brakes work at all, but the rears definitely lock.

The rear axle, brakes included, as well as the brake line from the proportioning valve to the rear, and the master cylinder are off of my wrecked 73 Ventura that was on the road 7 months ago. The front brakes are unknown (they are discs)

Any input is appreciated, before I start throwing money at it....
Thanks, Importsmasher

[Rob B]

What kind of brakes were on your wrecked 73 in the front? You need to keep the proportioning valve and master cylinder from the disc brake system on the 74 GTO. Brake bias will be different from a 4 wheel drum set up to a front disc set up.

[importsmasher]

Sorry, I should have mentioned that the 73 was a power disc brake car also, so all of the parts are the same.

Also, I have not bled the front brakes, so they may not be working at all. I will address that when the car comes back from the shop. Right now, the issue is that with a light pedal force, the rear brakes lock up violently.

Thanks,
Importsmasher

[Rob B]

Bleed the system first.

[Kyflier]

Yeah, sounds like air in the line to me.....

[importsmasher]

Just thought I would update in case anyone cares. After a move out of state, and a whole bunch of other things that got in the way, I got some work done on my 74 GTO. I rebuilt the front suspension and bled the whole system. I drove the car for the first time ever yesterday. The grabbing issue is gone now. However, when you come to a stop and release the pedal, you can feel the brakes still holding on, and let up after a couple of seconds. I am thinking it would be the brake booster....any opinions? Could it be the proportioning valve?
Thanks,
Importsmasher

[post toastie]

Check the soft brakeline that hooks to the rear axle.

[importsmasher]

In case anyone is interested, my problem(s) have been solved. The old rear I had in the car used to leak a little gear oil. I used the same brakes, backing plates and drums when I went to the Moser axle in the Ventura in 2008. I drove the car on the street with these brakes without any issues, until I wrecked it in 2009. Once I transferred the drive train to the 74 GTO, I started having the brake grabbing issues. Apparently the gear oil on the brake shoes got gooey (perhaps from sitting?), and transferred to the drums (it was hard to get off). When I drove the car for the first time last year, I must have gotten them hot enough to work or something, because the issue came back the next time I moved the car (It isn't registered yet so I have not driven it). Anyway, the shoes were grabbing the drums so hard that it broke the return springs on the passenger side (it would violently lock the rear brakes). I replaced them last weekend, and the grabbing problem was still there, so finally, I replaced the shoes, and sanded the gunk off the drums, and all is now well.....

I feel kind of dumb, as I had thought this might be the problem for a while, but I kept telling myself, "they worked fine on the other car, and nothing has changed," so I was looking elsewhere for the problem. I have had gear oil and/or brake fluid get on brake shoes in the past, and I have always just cleaned them off and kept on going (after fixing the leak, of course).

Importsmasher