76 blazer steering locks up at speed
 

I got a 76 and the steering is locking up when i get up to speed, about 30 mph or so. i just put on a new pump and its still doing it. its weird because it locks up more to the left. meaning the wheel is straight, i can move it a little to the right but none to the left. unless i jerk it really hard then it'll move. i cant figure it out. i bled the pump by jacking it up and turning the wheels left and right forever, still does it. i disconnected the high pressure line at the gearbox for a few seconds. still does it. any suggestions? does the gearbox have a bleeder valve that i need to utilize?

So is it related to ground speed or engine speed? As in, if you were to put the transmission in neutral & rev the engine to match the RPMs where the condition exists while moving, can you recreate the lock-up or is it ok?

What size tires do you have on it?

Running 36" tires. It was related to ground speed, engine speed didn't affect it. I replaced the gearbox and it fixed it. In fact I have never felt an old chevy with such crisp steering.